Thursday, March 08, 2007

Belluschi, Pietro

Belluschi, Pietro (1899-1994), Italian-born American architect, whose innovative work established a northwestern regional style. His planned community (1942) at McLaughlin, Washington, included the first modern shopping center, and his Equitable Savings and Loan Association Building (1948) in Portland, Oreg., was the first postwar curtain-wall skyscraper.

(August 18, 1899 - February 14, 1994) was an architect, a leader of the Modern Architecture movement, and responsible for the design of over one thousand buildings. He was a principal at the Portland, Oregon office of the Chicago architecture firm Skidmore, Owings and Merrill.

His designs include:

He also served as dean of the M.I.T. School of Architecture. He was awarded the Gold Medal of the American Institute of Architects in 1972.

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Thursday, February 15, 2007

Folk Art

Folk Art, carvings, paintings, needlework, decorated utensils, and other artifacts created by artists and artisans—often anonymous—who have no formal academic training in the arts. Folk art has existed in every culture, past and present. Of necessity, this article is restricted to folk art in North America produced by colonists and émigrés from Europe and Africa and by native Americans working in European styles. For the folk art of other cultures, see African Art and Architecture; Native Americans: Crafts and the Arts; Furniture; Glass; Inuit; Lace; Log Cabin; Mask; Needlework; Oceanian Art and Architecture; Pottery; Quilting; Silhouette; Stencil; Tattooing; Wood Carving.

Carved Native American Figure This figure of a Native American trapper was carved from a single pine log (about 1850-1890). The figure is not that of the typical “cigar store Indian.” The unknown artist chose to dress his trapper in the buckskin pants, suspenders, shirt, and hat commonly worn by white trappers and frontiersmen. The decorative wooden pieces attached to the figure’s legs and arms were originally plugs for bottles and jugs.Smithsonian American Art Museum/Art Resource, NY

The Western world has long distinguished between the highly structured teachings of the academies that produce the fine arts and the orally transmitted traditional arts, created by and for the artistically less sophisticated. In the conservative view held by many folklorists, for a work to qualify as folk art it must be part of a long-standing tradition, must be learned from an active practitioner, and its genre, style, and technique should be those of an isolated culture, such as that of the Amish or whalers.

In fine art the idiosyncratic is admired, whereas anonymity of style is characteristic of folk art...

In the United States and Canada the concept of folk art is far less restrictive. In the normal usage of museums, dealers, collectors, and the general public the key word is nonacademic—art that has developed outside, but not necessarily uninfluenced by, the arts taught in art schools. In fine art the idiosyncratic generally is admired, whereas anonymity of style is characteristic of folk art, in that it expresses an aesthetic for a specific group that includes the artist and the artist’s immediate audience.

Included in this broader concept current in America are such products as were created by teams of workers: circus-wagon carvings, carousel figures, and manufactured weather vanes. Paintings by artists of little or no training are included; many of the paintings in collections of folk art, however, are by artists with an awareness of academic mannerisms either through prints, an occasional viewing of an academic painting, or chapbooks (small books or pamphlets) on painting, such as those written by Rufus Porter (see below). Also included in the broader concept are the works that were produced by young people in seminaries and academies, such as memorials, needlework pictures, and calligraphic pictures.

An inclusive definition, then, of what is generally understood to be folk art in North America includes both traditional folk arts handed down from one individual to another—such as frakturs (illuminated writings), quilts, and scrimshaw—and other nonacademic objects that might be called associative folk arts. Such nonacademic objects have been included, for all practical purposes, in the literature and in the exhibitions of folk art for more than half a century. Often in this latter group are portraits sometimes designated as provincial, naive, or vernacular.

Another distinction is that between folk art and craft. If the utility of a work predominates, then it is a craft object; if decoration predominates, then it is an example of folk art.


In general, the same types of folk art are found on either side of the Canadian-U.S. border. There are differences, however, in style and emphasis that are derived from the differences in historical development.

A French-Canadian Folk Art

Obviously, the oldest traditions are in Québec and other French communities. As early as 1670, under the sponsorship of Bishop François de Laval, a school was founded near Québec where carving, painting, and other crafts were taught to the sons of the habitants (French settlers). Although its primary purpose was to provide art for the churches, it seems to have nurtured a carving tradition that survives to this day.

The predominant theme in Canadian folk carving is religious, especially the crucifix intended for the family shrine, but there is a considerable body of minisculpture, predominantly of birds and animals. The carving of animals may well have derived from the animals made for the crèches that were popular both inside and outside the homes. One ubiquitous figure is, of course, the beaver, symbol of Canada, which appears as a decorative element on a wide variety of objects and as a subject of carving in life-size. Carvings, usually of pine, were often painted in bright colors, reflecting the exuberant use of color inside and outside the French-Canadian home. In contrast, the figures on the crucifixes were often painted with a white finish similar to enamel.

... wide woven belts that young Native American women were taught to weave by Ursuline nuns.

The weather vane is still seen on country churches and barns. Most often it is in the form of a cock, either of wood or tin, but made in the round rather than in flat profile. Three other forms of folk art are common and characteristically French-Canadian: the small carved wooden pipes that go back to the days of the voyageurs; the carved molds for maple sugar, with such designs as maple leaves, snowshoes, and abstractions; and the handsome flèches—wide woven belts, colored by natural dyes, that young Native American women were taught to weave by Ursuline nuns. The overall spirit of French-Canadian folk art is colorful, happy, and, at the same time, devout.

B Anglo-Canadian Folk Art

The English tradition in the Maritime provinces is strong in the decoration of utilitarian objects, in graining, marbling, and incising, and in ship carvings (both figureheads and stern-board decorations). The emigration to Canada of many New Englanders during and after the American Revolution led to interesting similarities between eastern Canadian and New England arts, not only in ship carving but also in quilt patterns, hooked rugs, and full-scale sculptures. Such sculptures have been an especially strong tradition in Nova Scotia, continuing to the present time. The Anglo-Canadian Atlantic seaboard also seems to have produced a livelier painting tradition—mostly seascapes and ship portraits—than did French Québec.

C Swiss and German Folk Art

Ontario received many Empire Loyalists at the time of the Revolution, and they were soon followed by Swiss and German immigrants, mostly members of Amish, Mennonite, and other austere sects. Some came from Pennsylvania, but others came directly from Europe. In either case, they kept their own carefully circumscribed cultures intact, continuing and developing the colorful creation of frakturs of all types—birth and wedding certificates, religious texts, and merit awards—which were hardly known to the outside world until recently. They also kept alive a vigorous needlework tradition, including quilting and crocheting.

D Other European Folk Art

Like the western U.S., the Prairie provinces of Canada were settled late. They attracted not only Anglo-Canadians but also a wide variety of peoples from central and eastern Europe: Russian Doukhobors in Saskatchewan and Ukrainians throughout the Prairie provinces. Among these 20th-century pioneers a sprightly painting tradition developed, some of it depicting memories of earlier times in Europe, but far more often depicting the vast prairies and pioneer life. These paintings, naive and explicit, have a direct and sometimes powerful impact.

Derived from many ethnic groups and extending over three centuries, Canadian folk art is varied and handsome. The collection and exhibition of folk art has only recently come into its own in Canada, and it is likely that much Canadian folk art remains to be discovered.


Folk art created by settlers in the U.S. distinctly reflects the cultures of at least eight European countries—England, the Netherlands, Germany, Switzerland, Moravia, Norway, Sweden, and Spain—and of many nations on the African continent (see American Art and Architecture).

A English Influences

Painted Wood Figurehead This is a painted wood figurehead from early 19th-century England and was probably used on a military vessel. This piece and others like it had an influence on the figureheads made in the United States, although this one is much more elaborate than its American counterparts.

Although the history of English and Scottish folklore collecting dates from Samuel Pepys in the 17th century, and folklore was vigorously collected throughout the 19th century, almost no attention was paid to British folk art until recently. As a result, few collections of folk art are available in Great Britain with which to make comparisons to American colonial folk art. Such items as trade signs—both two-dimensional paintings and polychromed carvings—were a commonplace in Great Britain in the 17th century and were well established in the American colonies by the 18th century. The English tobacco-shop “black boys” are known to have influenced the early tobacco trade signs in America. Figureheads were a commonplace in Europe, but the predominance of British shipping in American ports unquestionably influenced U.S. wood sculptors who made stern-board carvings and figureheads. By the 19th century, American and British ship carvings were sometimes indistinguishable except for the figureheads depicting national heroes, and the American tendency toward greater simplicity.

... the women’s carved wooden busks (corset stays) were the undoubted precursors of...

British sources are easily recognizable in household folk art. Stenciling and an occasional fully painted wall were known in rural England, and the women’s carved wooden busks (corset stays) were the undoubted precursors of American scrimshaw busks of the great days of whaling. Carved buttermolds and some carving on other household utensils were part of the British tradition, but such carvings were better known on the Continent. British women coming to America brought needlework techniques that influenced their quilting, knitting, and crewel work. The rash of memorial pieces, both in needlework and watercolor, that sprang up after the death of George Washington in 1799 utilized motifs—the urn, the weeping willow, the church, and the mourning family—that had already been popular in Great Britain for some time. From the evidence currently available, the British seem not to have had a strong folk tradition of either portrait or genre painting; their influence was primarily in woodcarving and needlecrafts.

B Dutch Influences

The Dutch in the upper Hudson Valley brought with them the enthusiasm for painting that had made 17th-century Dutch art one of the cultural achievements of the age.

In the first half of the 18th century merchant families happily patronized provincial painters of Dutch and English origin for portraits. The names of the 150 or so sitters for these portraits have been known for many years, but the names of the artists are only just now beginning to surface: They include John Heaton, Nehemiah Partridge, and Pieter Vanderlyn, among others as yet unidentified. In many cases the poses and the decorative elements are borrowed directly from English mezzotints of the works of court painters of the previous century. The result, however, is anything but courtly: The portraits have a blunt directness about the faces, a joy in bright colors, a woodenness of the figures that mark them as the work of painters operating outside the fine-arts tradition.

Presumably, some of these same painters turned out the religious paintings, based on woodcuts in Dutch family Bibles, that were noted by several 18th-century visitors to the Albany region. Today, 38 such paintings have come to light, and for about half of these, the source is known.

The contribution of the Dutch to American folk art lay primarily in their enthusiasm for painting and their encouragement of colonial artists.

C “Pennsylvania Dutch” Influences

Pennsylvania Dutch Watercolor This Pennsylvania Dutch watercolor was painted about 1800 by an anonymous artist. It was probably intended to be a fraktur, or a reward-of-merit card given to students to commend academic merit or good behavior. The bird was most likely based on real birds that the artist saw every day.Scala/Art Resource, NY

The “Pennsylvania Dutch” were actually Germans, Swiss, Hollanders, and Moravians of German stock. Although many were members of pietistic sects—Amish, Mennonites, Dunkers—others were orthodox Lutherans. Industrious and pious, they secluded themselves (the pietists in particular) from external social and political affairs, followed their traditional ways, and maintained and nourished the folk arts they brought from Europe. Perhaps more than any other immigrant group they fulfilled the folklorists’ vision of an isolated people maintaining their own folkways against all inducements to do otherwise.

The common denominator among most of the Pennsylvania Dutch folk arts is a strong delight in color. Their fraktur manuscripts were painted in bright greens, yellows, oranges, Prussian blues, and reds. The same colors dominated their quilts, pottery, toleware, barn signs, and painted chests; even their delicious traditional foods were brightly colorful. Only their graceful metalwork lacked color—a deficit amply compensated for by strength of design.

Throughout these arts is woven a body of visual symbolism derived from the Bible, hymns, and sermons: the Tree of Life, the phoenix to symbolize death and resurrection, the self-sacrificing pelican (representing Christ), the tulip, the unicorn, hearts, parrots, peacocks, and symbols representing the sun. Typically associated with frakturs, many of these motifs also appear on quilts, on marriage chests, and in the carvings on domestic implements, creating a lively sense of image and color. The European art of wood carving flourished not only among the 18th-century Pennsylvania settlers and their descendants, but also among the immigrants of the following century. Among the latter were two carvers who came to be widely appreciated long after they were dead: Wilhelm Schimmel, admired for his whittled eagles, and John Scholl, a house carpenter, whose freestanding colorful celebrations are unique in the U.S.

D Norwegian and Swedish Influences

Despite the vigorous folk-art traditions in Scandinavia, the overall impact on American folk art of immigrants from northern Europe was relatively slight. Only recently have institutions such as the Vesterheim Norwegian-American Museum in Decorah, Iowa, and the Bishop Hill State Historic Site at Bishop Hill, Illinois, offered insight into these transplanted cultures. Each has added the name of one master to the list of American folk artists.

Lars Christenson arrived from Norway as a pioneer settler in Swift County, Minnesota, cleared his own land, built his own homes, served as a government employee, and helped to found the local Lutheran church. Like so many of his compatriots, however, his greatest satisfaction came from carving. He carved boxes and furniture for his own house, but in 1897 he began work on an intricately carved altarpiece (Vesterheim Norwegian-American Museum), 365.7 cm (12 ft) high by 304 cm (10 ft) wide. Using a great variety of woods, which he left unpainted, he merged his boyhood memories of Viking and Norwegian design with simplified versions of the French artist Gustave Doré’s biblical scenes. Like its counterparts in many churches on the west coast of Norway, it is a tripartite and tiered altar, embellished with carved flowers and angel heads. The Last Supper (after Leonardo da Vinci) and a crucifix with the two thieves occupy the center. This is one of the masterpieces of religious folk art made in America, symbolizing not only the religious sincerity of the carver but also the tradition of Scandinavian carving from which it derives.

Olaf Krans was born in Sweden and came to Bishop Hill, Illinois, with his parents in 1850. There they joined a religious commune of other Swedes. During his youth Krans watched (and remembered) how the prairie was broken, how the men and women sowed and reaped, how the settlers created a special enclave of their own on the rolling, fertile prairies. The paintings he began to create in his 50s are a remarkable record of one of America’s many utopian settlements in the years of its original enthusiasm. The long rows of planters and sowers, of reapers and gatherers, convey a sense of unity and dedication. Krans also did a gallery of portraits of the original settlers. Most are based on photographs, but he imparted to each portrait an insight drawn from his recollections and far surpassed the photograph in depiction of character.

Krans’s paintings are outside the mainstream of Swedish immigrant folk art, which, like that of the Norwegians, stressed woodcarving. Essentially this was a domestic art, its practitioners creating fine carved spoons, chairs, cupboards, and wooden boxes. Genre scenes in minisculpture reflect the life of the farm or lumber camp but were intended for the carver’s own home.

E Hispanic Influences

Wooden Polychrome Crucifix Many folk art expressions of Hispanic origin or influence are religious in character and exhibit similar distinctive features. The basic stylistic characteristics of the 17th-century wooden polychrome crucifix shown here, for instance, are typical of Hispanic folk art. The figure is elongated and simplified, and strong graphic details define the face, which effectively conveys emotion.Giraudon/Art Resource, NY

The Hispanic traditions come from two directions, the Southwest and Puerto Rico, and their most striking products are religious. New Mexico was generally neglected by Mexico after 1750, as routes going north bypassed it. It was then that local santeros (“saint carvers”) began to carve holy figures, bultos, for the isolated churches of the countryside. At the same time painters were developing a characteristic style of retablos (“altar paintings”). Stylistically, the carvings reverted to the first half of the 17th century, echoing the works of Andalusian followers of the Spanish sculptors Juan Martínez Montañés and Pedro de Meña. The bultos were of wood, the figures elongated, with strong graphic devices in faces and bodies. They convey an intensity of feeling that, even at a much later date and in a different culture, are gripping.

The retablos, although less impressive, are aesthetically attractive. Flatness characterizes them—little attempt is made to convey any sense of depth or roundness. The spaces are filled in with decorative details, and frequently the frame is painted. The aesthetic sources for the retablos are a century more recent than those of the bultos; they can be traced back to the followers of the Spanish master Bartolomé Esteban Murillo, painters who turned out devotional images for the New World.

Puerto Rico has a tradition of life-size religious figures, but more typical are the santos for the house shrine. Representing a person’s birth saint or the patron saint of a village, these figures are seldom more than 30 cm (12 in) high and are often smaller. They were made either by professional santeros or by the most skilled member of a family, and the carver invested meticulous care to ensure that the saint’s identifying symbol was made clear.

Although the santos were originally polychromed, many of the older ones that have long been handled and cherished have lost their paint and grown dark with age.

F African Influences

... veins of African culture: basketry, musical instruments, quilts, ceramics, wood sculpture...

The earlier assumption that when slaves were brought to the United States from Africa they came culturally empty-handed has now been exploded. The contributions of African tradition in work songs, blues, jazz, in certain musical instruments (the banjo, for example), and in folk narrative were beginning to be recognized in the 1930s. Only in the ‘60s and ‘70s, however, were the more subtle relationships to African visual arts identified. This recognition came partly as a result of long-overdue unified study of the areas of American folk art that most clearly reveal veins of African culture: basketry, musical instruments, quilts, ceramics, wood sculpture, ironwork, and grave decorations.

Of these, certainly woodcarving is the most widespread. Carved canes with snakes and alligators climbing up toward the handle, which was frequently a human head, are popular and are still being made. Plenty of other examples of carved figures and architectural carvings that spread across the South are also available: a cigar-store figure dated about 1800, a carved “throne” for a Presbyterian church, and any number of examples of minisculpture. They add up to a distinctive segment of American folk art, and all contain strong African echoes.


North American folk art was expressed in a variety of forms: painting, in both portraiture and landscape; carving, in stone, wood, metal, and ivory; pottery in profusion; and needlework, ranging from quilts and samplers to embroidered pictures.

A Painting

Ever since the first major museum exhibits of American folk paintings and sculptures, in the 1930s, nearly all collections of American folk art have included both paintings and three-dimensional materials. (In a few collections, the paintings are classified under the labels naive or primitive instead of being identified as folk art.)

A1 Portraiture

Mrs. Elizabeth Freake and Baby Mary Few American artists of the 1600s are known by name. One talented but unknown painter produced this portrait of maternal concern, Mrs. Elizabeth Freake and Baby Mary, in Massachusetts about 1674.Burstein Collection/Corbis

Because portraits were associated with family-oriented antiques and genealogy, they attracted attention long before other types of folk art. As early as the 1670s, New England portraitists, often called limners, were painting in an English vernacular style that dated from Tudor times. The best examples are those by the Gibbs and Mason limner (flourished late 17th century), who painted stiff representations of little girls and boys; and the Freake limner (flourished late 17th century), who painted the double portrait, Mrs. Elizabeth Freake and Baby Mary (circa 1674, Worcester Art Museum, Worcester, Massachusetts), both beautifully gowned in a manner quite contrary to the popular conception of Puritan dress.

Only after the American Revolution, however, did American portraiture—both academic and nonacademic—flourish. In the 60 years between the end of the American Revolution and the importation of photography to America, the London studio of the American expatriate painter Benjamin West became the great center for the training of American academic painters. For every American who went abroad to study, however, scores of sign painters, decorators, and glaziers in the U.S. felt their craftmanship entitled them to try their hands at portraits. With limited awareness of the traditions of academic portraiture, they set out to solve in their own ways such technical and aesthetic problems as perspective, proportion, and composition, often with inventive and striking results. Their emphasis was on the face, and they sought above all to achieve an accurate likeness.

Portrait of a Young Man This watercolor, Portrait of a Young Man, was painted in the 18th century, before the American Revolution. The artist may have been Robert Peckham, of Massachusetts. The style is closer to folk art than to the more sophisticated works of many of the painters of the Hudson River valley, and in fact it may have been created by a self-taught artist.Art Resource, NY

Many of these portrait painters were itinerants who went from one small town to another, putting up for a few days at a local inn. Because some of them repeatedly used the same pose and may have carried a handsome dress to lend their sitters, the misconception arose and was supported by early writers that in the winter artists painted bodies and then, when they found a client, added the head to the unfinished work. No canvas with a headless body has yet come to light, however, and no mention of such has appeared in any inventory of an artist’s estate.

New England, especially Connecticut, seems to have led in this popular movement to “get one’s likeness taken,” which soon spread to the mid-Atlantic states, although it was never popular in the South. The usual explanation is that the South never developed a significant middle class—the primary clientele of these nonacademic painters. With the invention of photography in 1839 and its immediate appearance in the U.S., came a rapid decline in portrait painting; a photograph was quicker and cheaper. Many of the painters became photographers themselves.

Limited space prohibits a catalog of the leading folk portraitists, but brief information about several can suggest how varied a group they were. For example, Joshua Johnston was one of the few black artists of the time; Ruth Henshaw Bascom was a clergyman’s wife; Deborah Goldsmith was a central New York itinerant who eventually married one of her sitters. John Brewster was a deaf mute, and Joseph W. Stock lived his adult life in a wheelchair but managed a wide-ranging itinerant career. James Sanford Ellsworth worked mostly in watercolor miniatures, with little clouds of glory behind the heads of his sitters, and, like a number of American folk artists, died in an almshouse. Finally, Ammi Phillips, who worked in the Hudson Valley, western Massachusetts, and Connecticut, developed at least three successive styles to meet the changing taste of his time; ironically, single paintings by Phillips today bring sums far larger than he earned in a long and arduous career.

A2 Landscapes

Portraiture was the most rewarding practice financially, but artists also painted landscapes, scenes of everyday life, and historical and religious subjects. The majority of folk painters of landscapes were copyists, using prints as their models, but other itinerants—such as Paul Seifert and Fritz G. Vogt—specialized in farm scenes, or, more accurately, in portraits of farms. Joseph Hidley was a genuine landscapist who painted charming scenes of his own village of Poestenkill, New York, and of neighboring towns. The great religious painter, Edward Hicks, depicted again and again (about 40 versions are extant) his sermon of the lion and lamb lying down together—his famous Peaceable Kingdom paintings—despite the negative attitude of his fellow Quakers toward art.

A3 Genre Scenes

School Scene, Pennsylvania Folk artists often create genre scenes, or images of everyday life. This genre painting, depicting children at a schoolhouse, was painted around 1920 by American folk artist J. C. Huntington. It is in the Smithsonian American Art Museum in Washington, D.C.Smithsonian American Art Museum/Art Resource, NY

The tendency of the naive artist to depict everything in great detail is of especial value when the genres, the scenes of everyday life, are considered. Often the paintings become historical documents filling in the lacunae left by the historian. Linton Park’s logging scenes and his Flax Scutching Bee are invaluable for conveying not only the facts but also the spirit of simple work situations. The black painter Clementine Hunter reflects far more than life on a cotton plantation; she conveys the moods of such a place. Another contemporary, Queena Stovall, depicts the seasons, the labors, and the rites of passage on a Virginia Piedmont farm as she experienced them.

A4 Decorative Painting

Many of the portraitists who started out as decorators and sign painters were multitalented artisans. In the late 18th and early 19th centuries, decorative stencils were used on the walls of rooms, floors, and furniture. Graining and marbling made simple pine look like far more expensive materials such as mahogany, oak, or imported marble. Most elaborate were the murals that covered all the walls of a room, with high mountains, ship-filled rivers, waterfalls, and companies of militia. Rufus Porter, a man of many skills, wrote a booklet on how to do all these things. When he founded the publication Scientific American in 1846, he expanded his earlier work to a series of 31 instructional articles; they covered everything from carriage painting to “Landscape Paintings on the Walls of Rooms.” Porter’s approach was neither aesthetic nor philosophical, but down-to-earth, to help his readers make a good living.

B Carving

America’s first sculptors... carved thedeath’s-heads, angels, and hearts and flowers on early gravestones.

Folk artists worked in many other media besides paint, the earliest being stone. America’s first sculptors were the stonecutters who carved the death’s-heads, angels, and hearts and flowers on early gravestones. With the exception of the religiously inspired carver William Edmondson, most later folk carvers have worked in wood.

B1 Wood Carving

All along the northern coast where ships were built, wood carvers, working closely with the ship architects, designed, carved, and painted the figureheads that gave each ship its individuality. As wooden ships disappeared from the seas, the carvers turned to making trade signs, especially tobacco signs—life-size Native Americans, Scots, ladies of fashion, and the like. By the last half of the 19th century these and the elaborate figures for circus wagons were being carved in large establishments where the product was no longer the creation of one carver but of many. For that reason, the later carvings are regarded as examples of associative folk art rather than of traditional folk art.

The same change in manufacture took place with weather vanes. The early examples in wood or metal were the products of one person’s imagination and skills, but by the end of the century they were produced by industrial plants; the only part of these later weather vanes that could be considered traditional folk art would be the original carvings from which the molds were cast. The most popular subjects for weather vanes were, again, Native Americans, but also horses, fish, and other animals, including, of course, roosters in all shapes and sizes.

B2 Scrimshaw

Scrimshaw The art of scrimshaw originated with sailors who employed this pastime to while away their spare time at sea. This piece depicts a whaling scene, a common motif in this folk art. Scrimshaw involves engraving a design on polished ivory with a sharp tool and then filling in the lines with ink. Today, scrimshanders, as they are called, use only fossilized ivory, and the industry is carefully monitored to make sure no one is using ivory from endangered species.Bridgeman Art Library, London/New York

By and large, the metal objects of folk art were utilitarian, but with strong decorative elements: implements with incised designs, lighting fixtures, and the weather vanes. The medium that really permitted the imagination of the folk artist to explode was work in ivory—the teeth and bones of whales—called scrimshaw. In moments of leisure aboard ship, whalers incised whale teeth with a wide variety of images and sentiments, patriotic, religious, erotic. They made scenes of their hazardous occupation on both teeth and bones; they also made busks for their women to wear inside their chemises, and thousands of pie crimpers, birdcages, clothespins, toys, swifts (yarn reels), walking sticks, and many other objects of use and beauty.

C Pottery

Although potteries were primarily engaged in turning out everyday ceramics for dining or storage, a small percentage of items exist in which the decorative elements outrank the utilitarian. For example, the redware dishes in the Pennsylvania Dutch German tradition, were enlivened with slipware designs and mottoes. Many of the stoneware potters painted blue designs on their jugs, jars, and coolers, offering two sources of pleasure in the shape of the object and in its decoration. The face jugs—black with white teeth and eyes—have recognizable African roots and often were made by black potters. Both supporters and opponents of the temperance movement expressed their points of view with jugs on which snakes had been molded before firing. Quite recently, individualized sculptural ceramics from sewer-tile factories have been discovered in Ohio, Michigan, and New York. These pieces should not be confused with those ceramic pieces from a mold, on which the touch of the artist is obscured.

D Needlework

Few women were portrait painters, but many were taught theorem and fancy painting in female seminaries. Women’s major contribution to American folk art, however, was in the realm of needlework.

D1 Samplers

In the colonial and early national periods girls were taught at a very early age a variety of stitches, including embroidered letters; these stitches, formed into a sampler, a kind of needlework diploma, proved the skills learned, with the name of the pupil and the date completed.

D2 Quilting

Welsh Patchwork Quilt This patchwork, or pieced, quilt from Wales was made in the early 19th century. The process involves sewing pieces of cloth edge to edge and then sewing the resulting piece to several other layers of cloth using a quilting stitch. The use of geometric design was common, and these patterns had to be planned out mathematically. Quilts made in the United States were often signed by the quilter.Bridgeman Art Library, London/New York

Women also cut and sewed the pieces of colored cloth that formed the designs of quilts. This work involved considerable mathematical comprehension and understanding of the nature of textiles, especially for the pieced quilt, in which the pattern was built up entirely from small bits of cloth (in contrast to the appliquéd quilt, in which a large cloth served as a ground for stitched-on patterns). During a time when all art was representational, women in rural America were creating thousands of examples of abstract art that can compete admirably with the abstract paintings of the present time. Since the early 1970s, many museums and art galleries have exhibited quilts as abstract art, thereby emphasizing the similarity in artistic aim.

D3 Embroidered Pictures

The needlework pictures that schoolgirls and young women created between the Revolution and the 1840s were often biblical scenes or memorials, generally embroidered in silk. Most of the picture was usually created with colored threads, with some details, such as faces, added in watercolor.


The thousands of Americans in Canada and the U.S. who have created this great body of aesthetically pleasing nonacademic art have left those countries greatly in their debt. Not only for their contemporaries but also for later generations, their works have amply fulfilled their primary objective—to give pleasure.

Major collections of folk art are at the Museum of Man in Ottawa, Ontario; the Abby Aldrich Rockefeller Folk Art Center in Williamsburg, Virginia; the New York State Historical Association, Cooperstown, New York; and the Museum of American Folk Art, New York City. So-called primitive or naive paintings from a major collection, the Garbisch Collection, are at the Metropolitan Museum of Art in New York City and the National Gallery of Art in Washington, D.C.

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Glass, an amorphous substance made primarily of silica fused at high temperatures with borates or phosphates. Glass is also found in nature, as the volcanic material obsidian and as the enigmatic objects known as tektites (see Tektite). It is neither a solid nor a liquid but exists in a vitreous, or glassy, state in which molecular units have disordered arrangement but sufficient cohesion to produce mechanical rigidity. Glass is cooled to a rigid state without the occurrence of crystallization; heat can reconvert glass to a liquid form. Usually transparent, glass can also be translucent or opaque. Color varies with the ingredients of the batch.

Tiffany Vase American designer Louis Comfort Tiffany helped popularize the art nouveau style with its elongated, curving, plantlike forms, in the United States in the late 19th century. This vase is an example of Favrile glass, a silky, opalescent glass that Tiffany developed.Victoria & Albert Museum, London, UK/Bridgeman Art Library, London/New York

Molten glass is plastic and can be shaped by means of several techniques. When cold, glass can be carved. At low temperatures glass is brittle and breaks with a shell-like fracture on the broken face. Such natural materials as obsidian and tektites (from meteors) have compositions and properties similar to those of synthetic glass.

Glass was first made before 2000 bc and has since served humans in many ways. It has been used to make useful vessels as well as decorative and ornamental objects, including jewelry. Glass also has architectural and industrial applications.


The basic ingredient of glass compositions is silica, derived from sand, flint, or quartz.

A Composition and Properties

Silica can be melted at very high temperatures to form fused silica glass. Because this glass has a high melting point and does not shrink or expand greatly with changing temperatures, it is suitable for laboratory apparatus and for such objects subject to heat shock as telescope mirrors. Glass is a poor conductor of both heat and electricity and therefore useful for electrical and thermal insulation. For most glass, silica is combined with other raw materials in various proportions. Alkali fluxes, commonly the carbonates of sodium or potassium, lower the fusion temperature and viscosity of silica. Limestone or dolomite (calcium and magnesium carbonates) act as stabilizers for the batch. Other ingredients such as lead and borax give to glass certain physical properties.

A1 Water Glass and Soda-Lime Glass

Glass of high soda content can be dissolved in water as a syrupy fluid. Known as water glass, it is used commercially for fireproofing and as a sealant. Most manufactured glass is a soda-lime composition used to make bottles, tableware, lamp bulbs, and window and plate glass.

A2 Lead Glass

Sayings of Confucius The Sayings of Confucius (1956), a contemporary glass sculpture by Donald Pollard and Cho Chung-Yeng, was produced by the Steuben Glass Company. This sculpture echoes the shapes of natural crystal, as well as the shapes of Chinese fans. The Chinese characters are etched into the glass.John White/Cooper Hewitt/National Museum of Design/Smithsonian/Art Resource, NY

The fine-quality table glass known as crystal. is made from potassium-silicate formulas that include lead oxide. Lead glass is heavy and has an enhanced capacity to refract light, which makes it suitable for lenses and prisms, as well as for imitation jewels. Because lead absorbs high-energy radiation, lead glasses are used in shields to protect personnel in nuclear installations.

A3 Borosilicate Glass

Borosilicate glass contains borax as a major ingredient, along with silica and alkali. Noted for its durability and resistance to chemical attack and high temperatures, borosilicate glass is widely employed for cooking utensils, laboratory glassware, and chemical process equipment.

A4 Color

Impurities in the raw materials affect the color of glass. For a clear, colorless substance, glassmakers add manganese to counteract the effects of iron traces that produce greens and browns. Glass can be colored by dissolving in it metallic oxides, sulfides, or selenides. Other colorants may be dispersed as microscopic particles.

A5 Miscellaneous Ingredients

Typical glass formulas include broken waste glass of related composition (cullet), which promotes melting and homogenization of the batch. Fining agents such as arsenic or antimony are often added to cause the release of small bubbles during the melting.

A6 Physical Properties

Depending on the composition, some glass will melt at temperatures as low as 500° C (900° F); others melt only at 1650° C (3180° F). Tensile strength, normally between 280 and 560 kg per sq cm (4000 and 8000 lb per sq in), can exceed 7000 kg per sq cm (100,000 lb per sq in) if the glass is specially treated. Specific gravity ranges from 2 to 8, or from less than that of aluminum to more than that of steel. Similarly wide variations occur in optical and electrical properties.

B Mixing and Melting

After careful preparation and measurement, the raw materials are mixed and undergo initial fusion before being subjected to the full heat needed for vitrification. In the past, melting was done in clay pots heated in wood- or coal-burning furnaces. Pots of fireclay, holding from 0.5 to 1.5 metric tons of glass, are still used when relatively small amounts of glass are needed for handworking. In modern glass plants, most glass is melted in large tank furnaces, first introduced in 1872, that can hold more than 1000 metric tons of glass and are heated by gas, oil, or electricity. The glass batch is fed continuously into an opening (doghouse) at one end of the tank, and the melted, refined, and conditioned glass is drawn out the other end. In long forehearths, or holding chambers, the molten glass is brought to the correct working temperature, and the vitreous mass is then delivered to the forming machines.

C Shaping

When working glass in its plastic state, five basic methods are employed to produce an almost limitless variety of shapes: casting, blowing, pressing, drawing, and rolling.

C1 Casting

In this process, known to the ancients, molten glass is simply poured into a mold and allowed to cool and solidify. In modern times centrifugal casting processes have been developed in which the glass is forced against the sides of a rapidly rotating mold. Capable of forming precise, lightweight shapes, centrifugal casting is used for the production of television-tube funnels.

C2 Glassblowing

Creating Glass Vessels These men are using the method of glassblowing to create glass vessels. The man on the left is sitting in a chair with a support for his blowpipe. He has already created the initial rough shape and is now refining the molten glass, using a pair of tongs, or jacks. The process he is using is called necking, the technique by which the glassblower creates the neck of a bottle or vase.Roger A. Clark, Jr./Photo Researchers, Inc.

The revolutionary discovery that glass could be insufflated and expanded to any shape was made in the third quarter of the 1st century bc, in the Middle East along the Phoenician coast. Glassblowing soon spread and became the standard way of shaping glass vessels until the 19th century. The necessary tool is a hollow iron pipe about 1.2 m (about 4 ft) long with a mouthpiece at one end. The glassblower, or gaffer, collects a small amount of molten glass, called a gather, on the end of the blowpipe and rolls it against a paddle or metal plate to shape its exterior (marvering) and to cool it slightly. The gaffer then blows into the pipe, expanding the gather into a bubble, or parison. By constantly reheating at the furnace opening, by blowing and marvering, the gaffer controls the form and thickness. Simple hand tools such as shears, tongs (pucellas), and paddles are used to refine the form, often while the glassblower sits in the special “glassmaker's chair,” one with extended arms to support the blowpipe. Blown glass can also be shaped with molds: Part-size molds pattern the gather, which is then removed and blown to the desired size. Full-size molds into which the gather is entirely blown impart size, shape, and decoration. Additional gathers may be applied and manipulated to form stems, handles, and feet, or they may be trailed on and tooled for decoration. A shaped bubble can be “flashed” with color by dipping it into molten glass of contrasting color. To make cased glass, a gather is placed within, and fused to, one or more layers of differently colored glass. For finish work and fire polishing at the mouth of the furnace, the gather is transferred to a solid iron rod called a pontil, applied opposite the blowpipe, which is then removed. When the pontil is cracked off it leaves a “pontil mark” that may be later ground or polished away.

In 1903 a fully automatic blowing machine was perfected, thereby making mechanical glassblowing possible.

C3 Pressing

Some pressing was involved in the production of ancient cast wares to ensure that the glass had full contact with the mold. Islamic artisans used simple handpresses to form glass weights and seals. European manufacturers rediscovered the technique in the late 18th century, using it to make decanter stoppers and the bases of stemmed tableware. In the 1820s patents were taken out, particularly in the U.S., that led to the development of fully mechanical pressing. In this process, a gather of glass is dropped into a mold, and a plunger then squeezes the glass between itself and the outer mold and forms the final shape. Both the mold and the plunger may be patterned to impart decorative design to the object being made.

C4 Drawing

Molten glass can be drawn directly from the furnace to make tubing, sheets, fibers, and rods of glass that must have a uniform cross section. Tubing is made by drawing out a cylindrical mass of semifluid glass while a jet of air is blown down the center of the cylinder.

C5 Rolling

Sheet glass, and plate glass in particular, was originally produced by pouring molten glass on a flat surface and, with a roller, smoothing it out prior to polishing both its surfaces. Later it came to be made by continuous rolling between double rollers.

D Lampworking

Lampworking consists of the reworking of preformed and annealed glass, generally to produce scientific laboratory equipment and decorative toys and figures. Rods and cylinders are reheated by air-gas or oxygen-gas flames and refashioned by hand or machine.

E Annealing

After being formed, glass objects are annealed to relieve stresses built up within the glass as it cools (see Annealing). In an oven called a lehr, the glass is reheated to a temperature high enough to relieve internal stresses and then slowly cooled to avoid introducing new stresses. Stresses can be added intentionally to impart strength to a glass article. Because glass breaks as a result of tensile stresses that originate across an infinitesimal surface scratch, compressing the surface increases the amount of tensile stress that can be endured before breakage occurs. A method called thermal tempering introduces surface compression by heating the glass almost to the softening point and then cooling it rapidly with an air blast or by plunging it into a liquid bath. The surface hardens quickly; the subsequent contraction of the slower-cooling interior portions of the glass pulls the surface into compression. Surface compressions approaching 2460 kg per sq cm (35,000 lb per sq in) can be obtained in thick pieces by this method. Chemical strengthening methods also have been developed in which, through an ion-exchange process, the composition or structure of the glass surface is altered and surface compression introduced. Strengths exceeding 7000 kg per sq cm (100,000 lb per sq in) can be attained by chemical strengthening.

F Decoration

Decorating Glass There are many different techniques for decorating glass. Some of these, such as cutting or engraving, are more often used on three-dimensional pieces. Painting or etching are usually used for flat glass, such as decorative windows or plates. Other techniques include gilding and sandblasting. The pieces here are an etched glass plate (left), a faceted cut glass vase (center), and a painted glass roundel (right).Victoria & Albert Museum, London;Beniaminson/Art Resource, NY;Aldo Tutino/Art Resource, NY

After annealing, a glass object may be embellished in a number of ways. Some of them are as follows:

In cutting, to produce cut glass, facets, grooves, and depressions are ground into the surface with rotating disks of various materials, sizes, and shapes and a stream of water with an abrasive. The steps are marking the pattern, rough cutting, smoothing, and polishing.

Designs are engraved by means of a diamond point or a metal needle, or with rotating wheels, generally of copper.

In the etching process intaglio decoration is achieved with acid, the results varying from a rough to mat finish.

In sandblasting, fine grains of sand, crushed flint, or powdered iron are projected at high speed onto the glass surface, leaving a design in mat finish.

In cold painting, lacquer colors or oil paints are applied to glass but are not affixed by firing.

In enamel painting, enamel colors are painted and then fused onto the surface in a low-temperature firing.

In gilding, gold leaf, gold paint, or gold dust is applied to glassware and sometimes left unfired; low-temperature firing, however, is necessary for permanency.


Archaeological evidence indicates that glass was first made in the Middle East, sometime in the 3rd millennium bc.

A Ancient Glass

The earliest glass objects were beads; hollow vessels do not occur before about 1500 bc. Asian artisans may have established the glass industry in Egypt, where the first vessels date from the reign (1479-1425 bc) of Thutmose III. Glass production flourished in Egypt and Mesopotamia until about 1200 bc, then virtually ceased for several hundred years. In the 9th century bc, Syria and Mesopotamia emerged as glassmaking centers, and the industry spread throughout the Mediterranean region. In the Hellenistic era, Egypt, because of the glassworks at Alexandria, assumed a leading role in supplying royal courts with luxury glass. It was on the Phoenician coast, however, that the important discovery of glassblowing occurred in the 1st century bc. In the Roman period glassmaking was undertaken in many areas of the empire, from Rome to Cologne.

A1 Early Techniques

Phoenician Glass Flask This Phoenician glass unguent flask from the 5th century bc was made using the core technique, which preceded glassblowing. A mixture of clay and dung was attached to a rod and formed into the shape of the flask. Hot threads of glass were wound around the form, smoothed, reheated, then wound with more glass. This process was repeated until the vessel was finished, and handles, a foot, and a lip were added. The rod, along with the core material, was then removed.Bridgeman Art Library, London/New York

Before the invention of the blowpipe, several methods existed for shaping and embellishing objects of colored glass, both translucent and opaque. Some articles were carved from solid blocks of glass. From potters and metalworkers glassmakers adapted casting processes, pouring molten glass into molds to produce inlays, statuettes, and open vessels such as jars and bowls. Preformed rods of glass could be heated and fused together in a mold for a “ribbon” glass. Patterns of great complexity were achieved by a mosaic technique, in which elements, fused in a rod, together made a design in cross section. Slices of such rods could be arranged in a mold to shape a vessel or plaque and then heated to fusion. “Gold band” glasses featured irregular bands of different colored glass, with gold leaf embedded in one translucent band.

The majority of pre-Roman glasswares were fashioned by the core technique. A mixture of clay and dung was fixed to a metal rod and given the internal shape of the desired vessel. It was dipped into a crucible of molten glass or was wound with threads of glass. The object was constantly reheated and smoothed on a flat stone. Threads of different colored glass were trailed on and combed, creating striking feather patterns, as seen on Egyptian glass of the 18th and 19th dynasties. Handles, feet, and the neck were added and the object cooled. The rod was withdrawn and the core material picked out. Only vessels of limited size, such as cosmetic containers and small vases, could be made this way. Later core-formed articles from the 6th century bc closely followed the forms of Greek pottery (see Pottery).

A2 Roman Glass

Roman Glassware These examples of early Roman glassware date from the 1st and 2nd centuries, when colorless glass had become more popular than opaque and colored styles. The four pieces on the left are burial pieces; the piece on the right was probably used as a jug for water or wine.Bridgeman Art Library, London/New York

Glassblowing, a less expensive and time-consuming method of manufacture, spread from Syria to Italy and other parts of the Roman Empire, gradually superseding the old techniques. A new taste in glass styles developed: The earlier manufacturing processes emphasized color and pattern; blowing enhanced the thin, translucent qualities of the material. Also, by the end of the 1st century ad, colorless glass supplanted colored glass as the most fashionable sort. Glassblowing made large-scale production possible and changed the status of glassware to an everyday material, used for windows, drinking vessels, and containers of all kinds.

The structure of the empire doubtless fostered the extraordinary developments in glassmaking that occurred in this period. Most of the known decorative techniques were invented by artisans of the Roman era. Blown glasswares were patterned in part and full-size molds. Such molds enabled novelty items such as head-shaped flasks to be produced in quantity. A delicately patterned ewer (1st century ad) in the Corning Museum of Glass, Corning, New York, is one of a remarkable group of mold-blown objects that bear the names of their makers. Some Roman glass has elaborately threaded and tooled decoration. Glasswares could be painted with religious and historical scenes, or could feature designs in gold leaf pressed between two layers of clear glass. Ancient glassmakers adapted lapidary skills to make lathe-cut, carved, and engraved glass of considerable beauty. In cameo glass, layers of different colored glass were fused together and then carved so as to leave contrasting motifs in relief. Best known of Roman cameo glass is the Portland Vase (1st century ad, British Museum, London), which depicts the myth of Peleus and Thetis. Delicate effects were achieved in the diatreta, or caged cups, in which great portions of the outer surface were cut away, leaving an intricate openwork frame that appears to stand almost free of the vessel within. The famous Lycurgus Cup (4th century ad, British Museum) epitomizes this practice.

B Western Glass

The manufacture of household glass suffered a general decline in the West with the fall of the Roman Empire.

B1 Medieval Glass

Rose Window, Notre Dame The north rose window of the Cathedral of Notre Dame, Paris, was built by Jean de Chelles from 1240 to 1250. It is 129 m (43 ft) in diameter and consists of brilliantly colored pieces of glass with lead around each piece, held in an iron framework. The details in the religious scenes are painted on the glass.Bridgeman Art Library, London/New York

Under Frankish influence glassmakers in northern Europe and Britain continued to produce utilitarian vessels, some of new, robust forms. The decoration of these objects was limited to simple molded patterns, threading, and applied ornaments such as prunts (blobs of glass). Mostly green in color, the glass was at first a soda-glass composition made with ashes of marine plants imported from the Mediterranean, as they had been during Roman times. By the late Middle Ages, however, soda was no longer available, and northern glassmakers turned to the wood ash from their own wood-fired furnaces as a flux, for a potash-lime glass. Because the glasshouses were situated in the forests that provided fuel and ash, the glass made was called forest glass, waldglas. Common glass in the waldglas style continued to be made in the lesser European factories until modern times.

The glory of Western glassmaking in the medieval period, through patronage of the church, was mosaic glass in Mediterranean Europe and stained-glass windows in the north (see Mosaics; Stained Glass). Mosaics were made of small glass cubes, or tesserae, embedded in cement. The tesserae, cut from solid cakes of glass, could be extremely elaborate, with gold and silver lead inlaid. Little is known of the production of mosaic glass before the 14th century.

Glass windows in churches are mentioned in documents as early as the 6th century, but the earliest extant examples date from the 11th century. The finest windows are considered those from the 13th and 14th centuries, primarily in France and England. Glasshouses in Lorraine and Normandy (Normandie) may have provided much of the flat glass for medieval cathedral windows. The glass was colored, or flashed with color, and then cut into the shapes required by the design. Details were painted into the glass, often with a brownish enamel. The pieces were fitted into lead strips and set in an iron framework. The art declined in the late Renaissance but was revived in the 19th century.

B2 Renaissance to the 18th Century

Venetian Glass Ewer This fanciful boat-shaped ewer is an example of Venetian glass from the mid-16th century. It is made of cristallo glass, which gets its name from its resemblance to rock crystal. The design of this piece is attributed to Armenia Vivarini and combines blue glass with stamped designs and gold work.Bridgeman Art Library, London/New York

Although glassmaking was practiced in Venice from the 10th century on, the earliest known Venetian glassware dates from the 15th century. Concentrated on the island of Murano, the Venetian industry dominated the European market until 1700. The major contribution of the Venetians was the development of a highly refined, hard-soda glass of great ductility. Colorless and highly transparent, the glass resembled rock crystal and was known as cristallo.

The first cristallo wares were simple forms, often embellished with jewel-like enamel designs. Objects were also blown of colored and opaque glass. By the late 16th century, forms became lighter and more delicate. The blowers exploited the workable nature of their material to produce fanciful tours de force. A type of filigree glass was developed in Venice and widely imitated. With lacelike effect, opaque white threads were incorporated in the glass and worked into intricate patterns. Some vessels were blown entirely of opaque white glass and painted with enamels in the manner of Chinese porcelain. Novelties made of lampworked glass were made at Murano, but Nevers, France, became most famous for this type of ware by the 17th century. Particularly suited to soda glass was the practice of diamond-point engraving, a technique favored in the 17th century by Dutch artisans. By hammering the diamond-point stylus for a stippled effect, they created ambitious pictorial designs.

Glass manufacturers throughout Europe tried to copy the Venetians in their production methods, materials, and decorative vocabulary. Knowledge was spread through the glasswares themselves, through the Art of Glass (1612) by Antonio Neri, and through Venetian glassblowers. Although forbidden by law to leave Venice and to divulge the secrets of their craft, many Murano glassmakers left Italy to set up glasshouses elsewhere in Europe. Each country developed its own façon de Venise, as nationalistic preferences for certain forms or decorations tempered the Venetian model. Italy's influence was ultimately weakened in the 17th century by the development of new glass recipes in Germany and England.

Germany's potash-lime glass, thicker and harder than cristallo, was well suited to wheel-engraved decoration. Caspar Lehmann, at the court of Holy Roman Emperor Rudolf II in Prague, was largely responsible for the development of engraving in the early 1600s. Glass cutters and engravers in Nürnberg and Potsdam became famous for skillfully executed designs in the baroque manner. At the same time, the Germanic glasshouses continued their tradition of enameled and cold-painted glass.

The other improvement in glass that served to diminish Europe's reliance on Venice was the lead-oxide glass formulated (circa 1676) by George Ravenscroft in England. Softer, more brilliant, and more durable than the brittle cristallo, English lead glass was considered the finest glass of the 18th century. English table glass dominated the European and colonial markets and became a model for Continental production. English innovations of the mid-18th century were glasses with air or opaque-enamel twists encased in the stems. Among the most prestigious forms of the period was the English cut-glass chandelier. Lead glass, especially suited to cutting, reached its full potential in the neoclassical wares of the Anglo-Irish period (1780-1830).

B3 American Glass

Glassmaking was the first manufacture undertaken in America, with a glasshouse built at Jamestown, Virginia, in 1608. The first commercially successful glassworks was that of Caspar Wistar in Salem County, New Jersey, between 1739 and 1777. Immigrant German artisans there and at other factories produced bottles, windowpanes, and some table glass in Germanic styles. Henry William Stiegel sought to imitate English imported lead glass at his factory in Lancaster County, Pennsylvania, from 1763 to 1774. The most important glassworks built after the American Revolution was that of John Frederick Amelung in Frederick County, Maryland, which was in operation from 1784 to 1795.

B4 19th and 20th Centuries

Art Glass by Dale Chihuly Dale Chihuly, a leader in the art-glass movement in the United States, created these decorative glass pieces: Niijima Floats: Garnet Black and Mint Green Float with Dimple (1991); Niijima Floats: Snow White and Gold Leaf (1991); and Niijima Floats: Mottled Blue Black Float with Silver Leaf (1992). All are in the Smithsonian American Art Museum, Smithsonian Institution, in Washington, D.C.Smithsonian American Art Museum/Art Resource, NY

The stylistic history of glass in the 19th century is dominated by rapid advances in glass technology and by the rediscovery and adaptation of older methods.

Mechanical pressing, introduced in the U.S., was a cheap, fast means of production that greatly expanded the role of glass in the home and in industry. Before 1850, wares were pressed in intricate lacy designs that offset a cloudiness in the glass caused by contact with the cooler mold. Simpler designs popular from the 1840s on, known as pressed pattern glass, were available in many forms. The more expensive cut glass declined in favor because of the competition from pressed glass. Only about 1880 did cut glass regain some of its earlier popularity with the elaborate “brilliant” patterns, examples of great technical virtuosity that exploited the refractive properties of quality glass.

Beginning in the late 18th century, a number of Roman glassmaking techniques were revived and modified to suit neoclassical taste. Continental glass factories made a version of laminated gold-leaf glass, called zwischengoldglas. Cameolike effects were attained with encrusted sulphides, and actual cameo engraving and cutting were practiced by artisans beginning in midcentury, culminating in the work of Thomas Webb and Sons (founded 1837), a glasshouse in Stourbridge, England. Paperweights, popular from about 1845, were often made in a millefiori (thousand flowers) design recalling the mosaic glass of ancient times. Renaissance rock crystal inspired a technique of polished engraved glass in the late 19th century.

Bohemia continued to excel in wheel-engraved decoration with the work of such artisans as Dominik Biemann. Other methods, such as cased glass, were practiced in Bohemian factories and copied throughout Europe and the U.S. Chemical advancements led to new opaque colored glass such as lithyalin, which resembled semiprecious stones. Transparent enamels and stains were applied to vessels, paralleling the revival of stained-glass windows.

Inspired by the revivals of historical glassworking methods and spurred by the capabilities of improved chemical technology, glassmakers by 1880 were creating new styles of handworked glass, generally called art glass. These were mostly decorative and novelty forms, made in reaction to mass-produced wares. Between 1890 and 1910 the most fashionable styles reflected the international art nouveau movement. Louis Comfort Tiffany in the U.S., and Émile Gallé and the firm of Daum Frères (founded 1889) in France, were the leading proponents of the style. They produced glasses of naturalistic shapes, sinuous lines, exotic colors, and unusual surface effects, such as Tiffany's iridescent Favrile glass.

After World War I new interests in texture and formalized decoration emerged, seen in the designs of René Lalique and Maurice Marinot. Beginning in the 1930s, exquisitely clear, colorless lead glass, often engraved, was popularized by several Scandinavian and American firms.

A new era in glassmaking began in the early 1960s with the studio glass movement, led by the Americans Harvey Littleton and Dominick Labino. With small tank furnaces in studio settings, artisans explore glass as an artistic medium. Innovative sculptural forms and decorative techniques are being developed at workshops in the U.S. and around the world.

C Non-Western Glass

Glassmaking was not as strong a tradition in Islamic and Far Eastern countries as it was in the West. Forms and techniques developed that closely reflected their individual cultures; these, in turn, influenced Western forms.

C1 Islamic Glass

Mosque Lamp This mosque lamp from the early 14th century is an example of the kind of glasswork that had been produced in Islamic countries for 500 years. This piece features enameled decoration and is inscribed with three quotations from the Koran. It is dedicated to Beybars II.

The history of glass from the 8th through the 14th century focuses on the Islamic world of the Middle East. Earlier Sassanian traditions of carved glass were continued by Muslim artisans, who made high-relief cut (hochschnitt) vessels, many with animal subjects. Quality colorless glass with fine wheel-engraved designs was also produced. The possibilities for decoration were expanded with the introduction of fired-on enamel colors and gilding, techniques for which the glasshouses at ?alab (Aleppo) and Damascus were famous. From Egypt came the discovery of luster stains, which created lustrous metallic effects in browns, yellows, and reds on both pottery and glass. Mosque lamps, bowls, beakers, and bottles were painted in the rhythmic, geometric patterns of Islam. Their shapes and decorations influenced later Western production, particularly in Venice and Spain.

C2 Indian Glass

Glass was made in India as early as the 5th century bc, but the industry was not established until the Mughal period, and particularly in the 17th century. Forms included hookah bases, sprinklers, and dishes, usually gilded or enameled in floral patterns. In the 18th century the English East India Company sold quantities of English glass to the Indian market, some of which was then wheel-engraved by Indian artisans.

C3 Far Eastern Glass

Giant Carved Bottle, Ch'ien Lung Dynasty This bottle from the Ch’ien Lung Dynasty (1736-95) is typical of the style being produced at that time in China. It features a simple shape, with intricate scenes of Chinese life carved in red glass on top of the white glass surface. The elaborate design is a reaction to the simplicity of the Sung style that preceded it.Bridgeman Art Library, London/New York

Chinese-made glassware in the distinctive “eye bead” form, with inlays resembling eyes, has been excavated from Zhou (Chou) dynasty sites (1045?-256 bc). Early glass objects, often melted from imported preformed glass cakes, were small and were carved in close imitation of gemstones. The use of glass to simulate semiprecious stones for jewelry and later for snuff bottles is a recurring theme in Chinese glass. Few vessels of glass are known before the glassworks at the Beijing Imperial Palace was erected in 1680. Under the influence of the Jesuits at the Beijing court, blown glass vessels in Western European styles were produced. Glass in the Chinese idiom dominated 18th- and 19th-century production, however, featuring richly colored objects with carved and enameled decoration. The Chinese mastered the art of cameo cutting in glass. Chinese glass vessels are characteristically of simple, porcelain-inspired shapes, with thick, often multilayered walls and a waxy surface sheen.

No evidence exists of glass made in Japan before 200 bc. Some glass vessels in the forms of Buddhist relic bottles and cinerary urns are believed to date from the Asuka/Nara periods (ad 552-784), but glassmaking apparently ceased in the 13th century. The craft was revived about 1750.


The wide range of uses of the material has resulted in the development of a number of different types of glass.

A Window Glass

Window glass, in use since the 1st century ad, was originally made by casting, or by blowing hollow cylinders that were slit and flattened into sheets. The crown process was a later technique, in which a gather of glass was blown and shaped into a flattened globe or crown. The pontil rod was attached to the flat side, the blowpipe removed. By spinning the reheated crown on the rod, the hole left by the blowpipe enlarged, and eventually the disk, through centrifugal force, flapped out in a large circular sheet. The pontil rod was cracked off, leaving a scar, or bull's-eye. Today, nearly all window glass is made mechanically by drawing glass upward from a molten pool fed from a tank furnace. In the Fourcault process the glass sheet is drawn through a slotted refractory block submerged in the surface of the glass pool, into a vertical annealing furnace from which it emerges to be cut into sheets.

B Plate Glass

Ordinary drawn window glass is not entirely uniform in thickness because of the nature of the process by which it is made. The variations in thickness distort the appearance of objects viewed through panes of the glass.

The traditional method of overcoming such defects has been the use of ground and polished plate glass. Plate glass was first produced at Saint Gobain, France, in 1668, by pouring glass into an iron table and rolling it flat with a roller. After annealing, the plate was ground and polished on both sides. Plate glass is now made by rolling the glass continuously between double rollers located at the end of a forehearth. After the rough sheet has been annealed, both sides of it are finished continuously and simultaneously.

Grinding and polishing are now being supplanted by the cheaper float-glass process. In this process flat surfaces are formed on both sides by floating a continuous sheet of glass on a bath of molten tin. The temperature is high enough to allow the surface imperfections to be removed by fluid flow of the glass. The temperature is gradually lowered as the glass moves along the tin bath, and the glass passes through a long annealing oven at the end.

Unpolished rolled glass, often with figured surfaces produced by designs incised in the rolls, is used architecturally. Wire glass, made by introducing wire mesh into the molten glass before it passes between the rollers, is used to prevent the glass from shattering if it is struck. Safety glass, for automobile windshields, is made by laminating a sheet of transparent polyvinyl butyral plastic between two sheets of thin plate glass. The plastic adheres tightly to the glass and holds the broken shards in place even after hard blows.

C Bottles and Containers

Bottles, cosmetic jars, and other glass containers are produced by an automatic process that combines pressing (to form the open end of the container) and blowing (to form the hollow body of the container). In a typical automatic bottle-blowing machine, a gob of molten glass is dropped in a narrow, inverted mold and forced down by an air blast into the lower portion of the mold, which corresponds to the neck of the finished bottle. A baffle then drops over the top of the mold, and a blast from the bottom, up through the neck, partly forms the bottle. The half-formed bottle, called a parison, is held by the neck, inverted, and then lowered into a second finishing mold, in which another air blast blows it out to its finished dimensions. In another type of machine, used for large-mouthed containers, the parison is simply pressed in a mold by a plunger before being blown in a finishing mold. Shallow jars, such as those used for cosmetics, are merely pressed.

D Optical Glass

Most lenses used in eyeglasses, microscopes, telescopes, cameras, and certain other optical instruments are made from optical glass (see Lens; Optics). Optical glass differs from other glass in the way in which it bends, or refracts, light. The manufacture of optical glass is a delicate and exacting operation. The raw materials must be of the highest purity, and great care must be taken so that no imperfections are introduced in the manufacturing process. Small air bubbles and inclusions of unvitrified matter will cause distortion on the surface of the lens. Striae, the streaks caused by incomplete chemical homogeneity in the glass, will also cause serious distortion, and strains in glass caused by improper annealing will further impair optical qualities.

Optical glass was originally melted in pots for prolonged periods, during which it was constantly stirred by a refractory rod. After a lengthy annealing, the glass was broken into pieces. The best fragments were further reduced, reheated, and pressed into the desired forms. In recent years a method has been adopted for the continuous manufacture of glass in platinum-lined tanks, using platinum-lined stirrers in the cylindrical end chambers (or homogenizers). This process produces greater quantities of optical glass that are cheaper and superior to glass produced by the earlier method. (Plastics are increasingly used in place of optical glass for simple lenses: Although not as durable and scratch resistant as glass, they are strong and lightweight and can absorb dyes.)

E Photosensitive Glass

Photosensitive glass is similar to photographic film in that gold or silver ions in the material will respond to the action of light. This glass is used in printing and reproducing processes. Heat treatment following an exposure to light produces permanent changes in photosensitive glass.

Photochromic glass darkens when exposed to light but fades to its original clear state when the light is removed. This behavior is achieved by the action of light on extremely small silver chloride or silver bromide crystals distributed throughout the glass. Photochromic glass finds a natural use in spectacle lenses that darken into sunglasses when in the sun and lighten again when removed from sunlight. The field of electronics also finds uses for this kind of glass.

F Glass Ceramics

Glass containing certain metals will form a localized crystallization when exposed to ultraviolet radiation. If heated to high temperatures, the glass will convert to crystalline ceramics with mechanical strength and electrical insulating properties greater than that of ordinary glass. Such ceramics are now made for such uses as cookware, rocket nosecones, and space-shuttle tiles. Other metallic glasses—including alloys of pure metals—can be magnetized, are strong and flexible, and prove very useful in high-efficiency electrical transformers.

G Glass Fibers

It is possible to produce fibers that can be woven or felted like textile fiber by drawing out molten glass to diameters of a few ten-thousandths of an inch. Both long, continuous multifilament yarns and short-staple fibers 25 to 30 cm (10 to 12 in) long may be produced.

Woven into textile fabrics, glass fibers make excellent drapery and upholstery materials because of their chemical stability, strength, and resistance to fire and water. Glass fabrics alone, or in combination with resins, make excellent electrical insulation. By impregnating glass fibers with plastics, a composite fiberglass is formed that combines the strength and inertness of glass with the impact resistance of the plastic.

H Miscellaneous Types of Glass

Fiber Optic Strands A strand of fiber optic cable reflects the light that passes through it back into the fiber, so light cannot escape the strand. Fiber optic cables carry more information, suffer less interference, and require fewer signal repeaters over long distances than wires.James L. Amos/Corbis

Glass bricks are hollow construction blocks with ribbed or patterned sides that can be laid in mortar and used for exterior walls or interior partitions.

Foam glass, used in floats or as insulation, is made by adding a foaming agent to finely ground glass and heating the mixture to the softening point. At that point the foaming agent releases a gas that produces a multitude of small bubbles within the glass.

In the 1950s glass optical fibers (see Fiber Optics) were developed that have many uses in science, medicine, and industry. High-refractive-index glass fibers, laid parallel to one another and separated by thin layers of low-refractive-index glass, can be optically worked as a lens. Fiberscopes incorporating such bundles can transmit an image through acute angles, thus easing the examination of normally inaccessible sites. Such solid fiber-optics applications as magnifiers, minifiers, and faceplates also improve viewing. When used in conjunction with lasers, optical fibers are also proving important in the development of various communications systems (see Telephone). A new kind of glass called halide glass, discovered in the 1970s, may prove especially useful for this application. It is made of a halide, such as fluorine, combined with a heavy metal, such as zirconium, barium, or hafnium.

Laser glass is doped, or mixed, with several percent of neodymium oxide and is capable of emitting laser light if the glass is pumped and assembled in the proper device. It is considered a good laser source because of the relative ease with which large, homogenous specimens of the glass can be obtained for extremely high-powered generation.

Double-glazing cells are units in which two sheets of plate or window glass are sealed together at their edges, leaving an air space between. Various types of seals and spacing materials may be used in their construction. As windows they provide superior heat insulation and will not cloud over in moist air.

A method for making large glass structures without using high temperatures was developed in the 1980s at the University of Florida. Called the sol-gel technique, it mixes water with a chemical such as tetramethoxysilane to produce a silicon oxide polymer; a chemical additive slows down the condensation process and allows the polymer to build up uniformly. The method may prove useful for making large, complex shapes with specific properties.

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Ceramics (Greek keramos, "potter's clay"), originally the art of making pottery, now a general term for the science of manufacturing articles prepared from pliable, earthy materials that are made rigid by exposure to heat. Ceramic materials are nonmetallic, inorganic compounds—primarily compounds of oxygen, but also compounds of carbon, nitrogen, boron, and silicon. Ceramics includes the manufacture of earthenware, porcelain, bricks, and some kinds of tile and stoneware.

Ceramic products are used not only for artistic objects and tableware, but also for industrial and technical items, such as sewer pipe and electrical insulators. Ceramic insulators have a wide range of electrical properties. The electrical properties of a recently discovered family of ceramics based on a copper-oxide mixture allow these ceramics to become superconductive, or to conduct electricity with no resistance, at temperatures much higher than those at which metals do (see Superconductivity). In space technology, ceramic materials are used to make components for space vehicles.

The rest of this article will deal only with ceramic products that have industrial or technical applications. Such products are known as industrial ceramics. The term industrial ceramics also refers to the science and technology of developing and manufacturing such products.


Ceramics possess chemical, mechanical, physical, thermal, electrical, and magnetic properties that distinguish them from other materials, such as metals and plastics. Manufacturers customize the properties of ceramics by controlling the type and amount of the materials used to make them.

A Chemical Properties

Industrial ceramics are primarily oxides (compounds of oxygen), but some are carbides (compounds of carbon and heavy metals), nitrides (compounds of nitrogen), borides (compounds of boron), and silicides (compounds of silicon). For example, aluminum oxide can be the main ingredient of a ceramic—the important alumina ceramics contain 85 to 99 percent aluminum oxide. Primary components, such as the oxides, can also be chemically combined to form complex compounds that are the main ingredient of a ceramic. Examples of such complex compounds are barium titanate (BaTiO3) and zinc ferrite (ZnFe2O4). Another material that may be regarded as a ceramic is the element carbon (in the form of diamond or graphite).

Ceramics are more resistant to corrosion than plastics and metals are. Ceramics generally do not react with most liquids, gases, alkalies, and acids. Most ceramics have very high melting points, and certain ceramics can be used up to temperatures approaching their melting points. Ceramics also remain stable over long time periods.

B Mechanical Properties

Ceramics are extremely strong, showing considerable stiffness under compression and bending. Bend strength, the amount of pressure required to bend a material, is often used to determine the strength of a ceramic. One of the strongest ceramics, zirconium dioxide, has a bend strength similar to that of steel. Zirconias (ZrO2) retain their strength up to temperatures of 900° C (1652° F), while silicon carbides and silicon nitrides retain their strength up to temperatures of 1400° C (2552° F). These silicon materials are used in high-temperature applications, such as to make parts for gas-turbine engines. Although ceramics are strong, temperature-resistant, and resilient, these materials are brittle and may break when dropped or when quickly heated and cooled.

C Physical Properties

Most industrial ceramics are compounds of oxygen, carbon, or nitrogen with lighter metals or semimetals. Thus, ceramics are less dense than most metals. As a result, a light ceramic part may be just as strong as a heavier metal part. Ceramics are also extremely hard, resisting wear and abrasion. The hardest known substance is diamond, followed by boron nitride in cubic-crystal form. Aluminum oxide and silicon carbide are also extremely hard materials and are often used to cut, grind, sand, and polish metals and other hard materials.

D Thermal Properties

Most ceramics have high melting points, meaning that even at high temperatures, these materials resist deformation and retain strength under pressure. Silicon carbide and silicon nitride, for example, withstand temperature changes better than most metals do. Large and sudden changes in temperature, however, can weaken ceramics. Materials that undergo less expansion or contraction per degree of temperature change can withstand sudden changes in temperature better than materials that undergo greater deformation. Silicon carbide and silicon nitride expand and contract less during temperature changes than most other ceramics do. These materials are therefore often used to make parts, such as turbine rotors used in jet engines, that can withstand extreme variations in temperature.

E Electrical Properties

Ceramic Circuit Package A technician’s gloved fingers hold a small semiconductor microchip housed in a ceramic package. The dark ceramic holds the gold-colored microchip at the center of the unit. This ceramic is a good electrical insulator and can conduct away heat generated by the microchip. Ceramic material separates the gold metal connections from one another so that electric signals stay on the correct path from the chip through the wire to the pin.Michael Rosenfeld/Tony Stone Images

Certain ceramics conduct electricity. Chromium dioxide, for example, conducts electricity as well as most metals do. Other ceramics, such as silicon carbide, do not conduct electricity as well, but may still act as semiconductors. (A semiconductor is a material with greater electrical conductivity than an insulator has but with less than that of a good conductor.) Other types of ceramics, such as aluminum oxide, do not conduct electricity at all. These ceramics are used as insulators—devices used to separate elements in an electrical circuit to keep the current on the desired pathway. Certain ceramics, such as porcelain, act as insulators at lower temperatures but conduct electricity at higher temperatures.

F Magnetic Properties

Ceramics containing iron oxide (Fe2O3) can have magnetic properties similar to those of iron, nickel, and cobalt magnets (see Magnetism). These iron oxide-based ceramics are called ferrites. Other magnetic ceramics include oxides of nickel, manganese, and barium. Ceramic magnets, used in electric motors and electronic circuits, can be manufactured with high resistance to demagnetization. When electrons become highly aligned, as they do in ceramic magnets, they create a powerful magnetic field which is more difficult to disrupt (demagnetize) by breaking the alignment of the electrons.


Industrial ceramics are produced from powders that have been tightly squeezed and then heated to high temperatures. Traditional ceramics, such as porcelain, tiles, and pottery, are formed from powders made from minerals such as clay, talc, silica, and feldspar. Most industrial ceramics, however, are formed from highly pure powders of specialty chemicals such as silicon carbide, alumina, and barium titanate.

The minerals used to make ceramics are dug from the earth and are then crushed and ground into fine powder. Manufacturers often purify this powder by mixing it in solution and allowing a chemical precipitate (a uniform solid that forms within a solution) to form. The precipitate is then separated from the solution, and the powder is heated to drive off impurities, including water. The result is typically a highly pure powder with particle sizes of about 1 micrometer (a micrometer is 0.000001 meter, or 0.00004 in).

A Molding

After purification, small amounts of wax are often added to bind the ceramic powder and make it more workable. Plastics may also be added to the powder to give the desired pliability and softness. The powder can then be shaped into different objects by various molding processes. These molding processes include slip casting, pressure casting, injection molding, and extrusion. After the ceramic is molded, it is heated in a process known as densification to make the material stronger and more dense.

A1 Slip Casting

Slip casting is a molding process used to form hollow ceramic objects. The ceramic powder is poured into a mold that has porous walls, and then the mold is filled with water. The capillary action (forces created by surface tension and by wetting the sides of a tube) of the porous walls drains water through the powder and the mold, leaving a solid layer of ceramic inside.

A2 Pressure Casting

In pressure casting, ceramic powder is poured into a mold, and pressure is then applied to the powder. The pressure condenses the powder into a solid layer of ceramic that is shaped to the inside of the mold.

A3 Injection Molding

Injection molding is used to make small, intricate objects. This method uses a piston to force the ceramic powder through a heated tube into a mold, where the powder cools, hardening to the shape of the mold. When the object has solidified, the mold is opened and the ceramic piece is removed.

A4 Extrusion

Extrusion is a continuous process in which ceramic powder is heated in a long barrel. A rotating screw then forces the heated material through an opening of the desired shape. As the continuous form emerges from the die opening, the form cools, solidifies, and is cut to the desired length. Extrusion is used to make products such as ceramic pipe, tiles, and brick.

B Densification

The process of densification uses intense heat to condense a ceramic object into a strong, dense product. After being molded, the ceramic object is heated in an electric furnace to temperatures between 1000° and 1700° C (1832° and 3092° F). As the ceramic heats, the powder particles coalesce, much as water droplets join at room temperature. As the ceramic particles merge, the object becomes increasingly dense, shrinking by up to 20 percent of its original size . The goal of this heating process is to maximize the ceramic’s strength by obtaining an internal structure that is compact and extremely dense.


Ceramics are valued for their mechanical properties, including strength, durability, and hardness. Their electrical and magnetic properties make them valuable in electronic applications, where they are used as insulators, semiconductors, conductors, and magnets. Ceramics also have important uses in the aerospace, biomedical, construction, and nuclear industries.

A Mechanical Applications

Industrial ceramics are widely used for applications requiring strong, hard, and abrasion-resistant materials. For example, machinists use metal-cutting tools tipped with alumina, as well as tools made from silicon nitrides, to cut, shape, grind, sand, and polish cast iron, nickel-based alloys, and other metals. Silicon nitrides, silicon carbides, and certain types of zirconias are used to make components such as valves and turbocharger rotors for high-temperature diesel and gas-turbine engines. The textile industry uses ceramics for thread guides that can resist the cutting action of fibers traveling through these guides at high speed.

B Electrical and Magnetic Applications

Ceramic materials have a wide range of electrical properties. Hence, ceramics are used as insulators (poor conductors of electricity), semiconductors (greater conductivity than insulators but less than good conductors), and conductors (good conductors of electricity).

Ceramics such as aluminum oxide (Al2O3) do not conduct electricity at all and are used to make insulators. Stacks of disks made of this material are used to suspend high-voltage power lines from transmission towers. Similarly, thin plates of aluminum oxide , which remain electrically and chemically stable when exposed to high-frequency currents, are used to hold microchips.

Other ceramics make excellent semiconductors. Small semiconductor chips, often made from barium titanate (BaTiO3) and strontium titanate (SrTiO3), may contain hundreds of thousands of transistors, making possible the miniaturization of electronic devices.

Scientists have discovered a family of copper-oxide-based ceramics that become superconductive at higher temperatures than do metals. Superconductivity refers to the ability of a cooled material to conduct an electric current with no resistance. This phenomenon can occur only at extremely low temperatures, which are difficult to maintain. However, in 1988 researchers discovered a copper oxide ceramic that becomes superconductive at -148° C (-234° F). This temperature is far higher than the temperatures at which metals become superconductors (see Superconductivity).

Thin insulating films of ceramic material such as barium titanate and strontium titanate are capable of storing large quantities of electricity in extremely small volumes. Devices capable of storing electrical charge are known as capacitors. Engineers form miniature capacitors from ceramics and use them in televisions, stereos, computers, and other electronic products.

Ferrites (ceramics containing iron oxide) are widely used as low-cost magnets in electric motors. These magnets help convert electric energy into mechanical energy. In an electric motor, an electric current is passed through a magnetic field created by a ceramic magnet. As the current passes through the magnetic field, the motor coil turns, creating mechanical energy. Unlike metal magnets, ferrites conduct electric currents at high frequencies (currents that increase and decrease rapidly in voltage). Because ferrites conduct high-frequency currents, they do not lose as much power as metal conductors do. Ferrites are also used in video, radio, and microwave equipment. Manganese zinc ferrites are used in magnetic recording heads, and bits of ferric oxides are the active component in a variety of magnetic recording media, such as recording tape and computer diskettes (see Sound Recording and Reproduction; Floppy Disk).

C Aerospace

Aerospace engineers use ceramic materials and cermets (durable, highly heat-resistant alloys made by combining powdered metal with an oxide or carbide and then pressing and baking the mixture) to make components for space vehicles. Such components include heat-shield tiles for the space shuttle and nosecones for rocket payloads.

D Bioceramics

Certain advanced ceramics are compatible with bone and tissue and are used in the biomedical field to make implants for use within the body. For example, specially prepared, porous alumina will bond with bone and other natural tissue. Medical and dental specialists use this ceramic to make hip joints, dental caps, and dental bridges. Ceramics such as calcium hydroxyl phosphates are compatible with bone and are used to reconstruct fractured or diseased bone (See Bioengineering; Dentistry).

E Nuclear Power

Engineers use uranium ceramic pellets to generate nuclear power. These pellets are produced in fuel fabrication plants from the gas uranium hexafluoride (UF6). The pellets are then packed into hollow tubes called fuel rods and are transported to nuclear power plants.

F Building and Construction

Manufacturers use ceramics to make bricks, tiles, piping, and other construction materials. Ceramics for these purposes are made primarily from clay and shale. Household fixtures such as sinks and bathtubs are made from feldspar- and clay-based ceramics.

G Coatings

Because ceramic materials are harder and have better corrosion resistance than most metals, manufacturers often coat metal with ceramic enamel. Manufacturers apply ceramic enamel by injecting a compressed gas containing ceramic powder into the flame of a hydrocarbon-oxygen torch burning at about 2500° C (about 4500° F). The semimolten powder particles adhere to the metal, cooling to form a hard enamel. Household appliances, such as refrigerators, stoves, washing machines, and dryers, are often coated with ceramic enamel.

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