To understand the nature of this art one needs to consider the material components of the stained-glass window and the various ways in which these are assembled; the architectural factors that govern the luminosity of stained glass and the resources of the medium for exploiting different degrees of luminosity; and the reasons for the singularly entrancing effect of 12th-and 13th-century stained glass. From the time of its origin to the present day the art of stained glass has undergone an interesting evolution.
Fabric of the Stained-glass Window. The art of making stained glass is not now and probably never was—for the designer, painter, or fabricator of stained-glass windows—essentially an art of coloring or literally staining glass. The technique of making colored glass is one thing, and the art of designing and making stained-glass windows out of such glass is quite another. The two skills stand in exactly the same relation as do the manufacture of oil paints and the art of easel painting.
Like nearly all other kinds of glass, stained glass is colored by the addition of various metal oxides to its basic ingredients while the glass is in a molten state. The glass is then made into sheets approximately 20 by 30 inches in size by an ancient technique that gives it very much the appearance of medieval glass. Hence its common trade name "antique" glass. The glassblower gathers an amount of molten glass on the end of a blowpipe and blows a bubble, which he manipulates into the shape of a bottle. He next cuts the end off the bottle, slits the remaining cylinder down one side, and then places the glass into an annealing oven, where it is gently flattened into a sheet. All glass made in this way is transparent and colored throughout with one basic color. Because it varies slightly in thickness, however, its color will often vary in depth, adding greatly to the beauty of the glass.
The basic steps in the making of a typical 13th-century stained-glass panel, "The Prophet Ezekiel," are as follows: From the design, or cartoon, a pattern is made, showing the exact shapes and sizes of the pieces of glass to be cut, and indicating the color for each piece, namely, R for ruby, W for white, and so on. A piece of glass of the proper color is selected for each area and cut to shape with a small interval of space between it and all adjacent pieces to allow for the leading. The details of the design—features, drapery, or whatever—are then "traced," often literally, onto the various pieces of glass with a dense, colorless enamel consisting of oxides and ground glass and mixed with a purely temporary aqueous glue binder, such as gum arabic. This paint can be applied either opaquely or in thin films so as to overlay the basic color of the glass with a purely tonal shading. While much of the shading has disappeared from the earliest windows or merged with the patina on the glass, it can be clearly seen in the very early and unusually well-preserved "Head of Christ" from Wissembourg. After the pieces are painted they are placed in a kiln and fired at a temperature that is not high enough to melt the glass but high enough to cause the glass paint to vitrify and fuse to its surface. When all the glass has been selected, cut, painted where necessary, and fired, it is assembled with flexible preformed strips of lead. These have an "H" cross section with grooves on either side to take the glass. They are fitted around all the pieces, and the joints are soldered, first on one side of the panel, then on the other. The panel is then waterproofed by scrubbing or pressing a putty compound under the leads. It is then completed and ready for installation in a window.
All but the very smallest stained-glass windows must, for purely structural reasons, be made in several sections and installed in some kind of frame or armature from which they will derive sufficient rigidity to withstand the pressures of wind and their own cumulative weight from top to bottom. This frame, far from being a mere structural necessity, has always been exploited by the most competent designers as a transitional link between the purely internal, pictorial, or ornamental composition of the window itself and the larger rhythms of its architectural setting. As will be seen below, the evolution of the stained-glass armature is one of the basic distinguishing characteristics of the art from century to century.
In the 13th century it was true without exception that each piece of glass consisted of but one basic color, so that each change of color in the image could be effected only by the introduction of another piece of glass of the second color and a line of lead between it and the first color. The skill with which the artisans of the period incorporated this leading into their designs is apparent when one compares almost any medieval window with a typical panel of the 16th century, e.g., the "Triumph of David," from the Abbey of Marienwald; but since this is essentially a problem of style, it is taken up in a later section of the article.
Two ways of modifying the color of a single piece of glass were discovered in the later Middle Ages. First,
in the 14th century it was discovered that glass could in fact be stained one color, yellow, with silver salts applied and fired like the vitreous glass paint already in use. Then in the 15th century two processes, flashing and abrasion, were combined to create another technique. Flashed glass is glass consisting of a basic color, usually somewhat light, upon which a thin film of a stronger color has been superimposed during the process of its manufacture. The glassblower creates it dipping his first bubble of glass into a second color before blowing the bottle from which the sheet of glass is made. From earliest times ruby glass had to be made in this manner because of the density of its coloring agent—hence the famous "streaky" rubies of the 12th-and 13th-century windows, which actually consist of several alternate layers of ruby and white. By grinding away parts of the flashed surface color it is possible to create patterns of the two colors, the flash and the base color, on a single piece of glass, which, moreover, can also be stained yellow and painted with tones and lines of the glass paint already described. In the 19th century the laborious technique of removing flashed colors by abrasion gave way to the much superior technique of etching them away with hydrofluoric acid. Except for this late refinement all of the practicable techniques of color
manipulation now known were perfected in the Middle Ages. The most significant 20th-century contribution to the craft was the development of two new materials that make possible the assembly of stained-glass panels without leads: slab glass and epoxy resin.
If instead of being blown into sheets of antique glass in the traditional manner (sheets that usually vary in thickness from one-eighth to three-sixteenths of an inch), glass is cast in slabs more nearly a full inch in thickness, it becomes almost another material—a rocklike, jewel-like substance that can be chipped and faceted and cast into panels with cement. Since a panel made in this way is actually a piece of masonry itself, it readily takes its place in the masonry wall as a very congenial and substantial part of it.
While epoxy resin is sometimes used as a binder in slab glass and concrete windows in lieu of lime, still another, more radical, use is made of the glue. Pieces of antique glass are cut, painted, and fired exactly as if they were to be leaded; but instead of being joined by leads, the pieces are glued to a sheet of plate glass with a clear variety of the resin. This provides them with a completely invisible support. Not only is the need for an opaque structural lead or concrete element within the stained-glass panel eliminated, but it is possible also to make the individual sections of an epoxy window several times as large as those of the leaded or slab glass window. The significance of this technique is still more of a promise than an actuality; but there is every indication that, just as slab glass has extended the range of the medium in the direction of massiveness, this technique will be used to create far lighter and more evanescent windows than have ever been technically possible heretofore. The architectural significance of these new techniques will become apparent in the next section.
Luminosity. Light is a uniquely pervasive and dynamic force in man's life. Since time immemorial the polarity of light and darkness has been almost universally felt and consciously accepted as a reflection of life versus death, awareness versus ignorance—as a natural counterpart of good versus evil, however these were culturally defined. Delight, dread; enlightenment, superstition; clarity, obscurity; brilliance, dullness—the complexities of man's attraction to light are so mingled that the expression of them cannot be affected by a truism. Nevertheless even the truism enables one to understand why stained glass, properly designed to exploit light in its particular architectural setting, can be so powerful an art form.
The normal range of light values within a stained-glass window is between 10 and 15 times as great as the range possible in the most vigorous opaque painting; in absolute brightness the white or clear glass in a stained-glass window is not uncommonly as much as 125 times as bright as even a white wall adjacent to it.
The apparent brightness of a stained-glass window is governed not by its absolute brightness, however, but by the difference between the amount of light that comes through it from the outside and the amount of light, natural or artificial, that strikes its inner surfaces. When indoors, one's eyes are adjusted not to the full intensity of daylight but to the general level of illumination indoors. In a typical 12th-century church, where the window openings are generally quite small and widely spaced, the basic interior light level, even with clear or unglazed windows, is quite low. The pupils of one's eyes must dilate considerably for him to see anything at all. The daylight that comes through its windows therefore appears brighter to the eye than it ever does out of doors or in a lighter interior. The apparent brightness of any window opening varies inversely with the light level inside it; and this light level is determined by the design of the space itself, by the relative amount of its wall surface opened up in order to admit light. It is the architect, therefore, more than the artist, who actually determines how luminous a stained-glass window can be. The darker the space he creates, the more brilliant a light source he creates for stained glass; the lighter the space, the more muted the light source will be.
Neither of these situations is inherently better than the other; but the failure to grasp the necessary relation between dark interiors and colors dense enough to avoid harsh, overbrilliant effects on the one hand, and light interiors and colors light enough not to become dull and murky on the other, might almost be called the lost art of stained glass. Contrary to popular belief, there is no color in medieval glass that glassmakers have not been able to match very closely for at least 100 years. As long ago as 1868 Viollet-le-Duc, restoring the French cathedrals, could claim that his workmen had "completed ancient windows with such a perfection of imitation that one cannot distinguish the restorations from the old parts." There is no question that the artists and architects of the Middle Ages understood this basic relation of dark-to-dark and light–to-light, for it is only where one finds a later window inserted into an earlier space, for example in the 15th-century Vendome Chapel in the 13th-century nave of Chartres, that one finds a medieval window out of key with its setting.
Given the brilliant, even harsh light created by the dark interiors of the 12th and 13th centuries, the glassmen of the time very logically worked with a schema of deep, saturated colors or, where only white glass could be afforded, painted the glass with a fine overall pattern of "grisaille" that breaks up and subdues the light. Later, as the walls of the high and late Gothic churches were opened up to admit more and more light, the point was soon reached where the difference between the outside and inside light levels was no longer great enough to illuminate fully the ruby-and-blue windows of the earlier churches. The artists of the 14th and 15th centuries were therefore obliged to work out a viable palette of lighter colors, colors that needed less light to bring them to life; it was the English who, utilizing yellow stain and white glass to maximum advantage, evolved in the 15th century the gold-and-silver windows, which are the final and logical major development in medieval stained glass.
It is obvious from the foregoing that what the newly developed techniques of slab glass and transparent epoxy have done is to extend the range of light controls within the medium, at the disposal of the artist, in both directions. Stained glass is thus technically a far more versatile art now than it ever was in the past.
Stained Glass of the 12th and 13th Centuries. To grasp what an overwhelming effect the stained glass of the 12th and 13th centuries must have had in its day, one has to visualize it in the context of a largely agrarian world dominated not by the paints, inks and dyes, electric lights, and neon signs of urban industrialized civilization, but rather by homespun and weathered wood, the greens and browns of the countryside. It was a world that had, in the words of Aldous Huxley, "a passionate thirst for bright, pure colors," and these the stained-glass windows in the early churches provided in an altogether unprecedented richness and abundance. It is evident also that for men such as Abbot Suger of Saint-Denis the splendor of stained glass must have had a significance over and above that of its particular subject matter. In his writings there are passages such as the following: "When—out of my delight in the beauty of the house of God—the loveliness of the many-colored stones has called me away from external cares, and worthy meditation has induced me to reflect, transferring that which is material to that which is immaterial, on the diversity of the sacred virtues: then it seems to me that I see myself dwelling, as it were, in some strange region of the universe which neither exists entirely in the slime of the earth nor entirely in the purity of Heaven; and that, by the grace of God, I can be transported from this inferior to that higher world in an anagogical manner."
To account for the continuing hold of these magnificent works on even the most casual visitor to the great cathedrals requires some analysis of their form as well as of their color and their luminosity. The predominant colors in them, ruby and blue, are deployed in a distinctive and powerfully affective way that can be almost transporting in itself: each of the principal colors keeps shifting its status in the composition of the windows from figure to ground or ground to figure in relation to the other. Scenes with blue backgrounds, for example, alternate with border areas in which figurative blue ornamental motifs are set off against a ruby background; and the artist has contrived to place bits of figurative blue or ruby adjacent to background blue or ruby. The result is an interlaced pattern of colors that one is forced to keep interpreting and reinterpreting from point to point and that never resolves into any one fixed and final form.
This is but one of the seemingly endless devices that the artisans of the time hit upon to imbue each part of their work with the quality of its opposite, and it was the indispensable formal device for linking their stained-glass windows with the larger architectural settings in which they were placed. Not only are the narrative medallions in 13th-century windows deployed ornamentally in the windows, but the armatures that support the glass reflect the adjacent structural order of the wall; also, the lyricism of the windows is echoed in the detailing of the stonework that frames them. To continue the sequence, the sculpture of the portals, though endlessly subtle in detail, is grouped architecturally, whereas the towers of the cathedrals are treated sculpturally; the manifold variety of silhouettes of the cathedral is resolved in its overall monumentality; and it stands, for all its complexity, as a landmark on the horizon.
Evolution of Stained Glass. The art of stained glass as it is now known begins with the five "Prophet" windows in the clerestory of Augsburg cathedral, thought to be the work of the monks of Tegernsee in the year 1065. Rigidly frontal, these windows seem to derive not only from the Italo-Byzantine mosaics of Rome, Venice, and Ravenna, but in drawing and to some extent color, from the Celtic manuscripts of St. gall in Switzerland. They are predominantly ruby, green, yellow, and wine-colored, with only a relatively small amount of pale blue in them, and are the only existing windows that predate the ruby-and-blue color scheme that was practically universal during the 12th and 13th centuries.
The most complete ensemble of 12th-century windows extant are those in the west façade of the cathedral of Chartres, dating from midcentury. Like the famous "La Belle Verriere" in the south aisle of the cathedral and the surviving glass of this period in Bourges and elsewhere, these windows are dominated by an incredibly luminous blue, against which are played ruby and a deep rose color and secondary accents of white, green, yellow, and a ruddy flesh tint. The windows were painted in the vigorous calligraphic manner of the Wissembourg "Head of Christ." The iron armatures had not yet become an actively ornamental device but were simply employed to divide the windows into panel-sized squares or rectangles. Within these squares, however, the individual episodes in a narrative window are usually framed by exuberantly ornamented borders in which the figure-ground status of the major colors is manipulated in the manner already described.
The 13th century saw the ruby and blue windows brought to their ultimate refinement. The wrought-iron armatures of the windows became an actively ornamental device in their own right, dividing the windows first into simple circular medallions, as in the very early example from Canterbury, and later into very handsome patterns of alternating or interlaced circles, lozenges, and quatrefoils. The 13th-century blue is generally a deeper, graver blue than that of the 12th century, although it is still a very saturated color; and the development of distinctive secondary color schemes within the basic ruby and blue is present. Thus, for example, in the nave of Chartres one window is largely green, white, and wine-colored in its secondary colors, whereas the next one emphasizes a smoky yellow and white, and so on.
After the heroic scale and rigorous order of the 12th and 13th centuries came the langorous windows of the 14th century. The window openings were subdivided into lancets and tracery of stone rather than ornamental iron-work, and the international ruby and blue color scheme gave way to a range of alternate schemes that took on increasingly regional characteristics as the century progressed, particularly after the hiatus caused by the Black Death (1350). Nearly everywhere there is more use of white, partially in order to let more light into the churches; partly to take advantage of the newly discovered technique of yellow staining; perhaps also because of a shortage of ruby and blue glass; and probably in simple reaction to a mood and style that had dominated the art for at least five or six generations. The figures and figure compositions became generally much larger and less complex than in the earlier medallion windows, and they were framed in canopies, which sometimes, as in Gloucester, became as elaborate as the figures themselves. The touchstone of 14th-century stained glass is the "Gothic sway" in the stance of its figures and in the simple flow of their garb, as in the detail from a choir window, Koenigsfelden.
By the end of the 14th century the die was cast. French stained glass, which had dominated the field for more than two centuries, began to slip into a hard, joyless competence from which it did not recover. German, Austrian, and Swiss stained glass was both retrospective, in its retention of the medallion composition and diapered backgrounds of the 13th century, and at the same time advanced, in adopting certain perspective devices from the proto-Renaissance art of Italy. For the 15th century, therefore, it is to England that one turns in order to follow the most purely medieval, and most genuinely creative, evolution of the art for another 100 years.
If the stained glass of the 13th century may be called a cathedral art because of its jewel-like richness and overall formality, that of the 15th century seems to be essentially an art of chapels and of parish churches, less architectonic, more intimate, and more concerned with the expression of human feeling. In the words of Émile Mâle, "the high Middle Ages rarely chose to depict any but the triumphant Christ; the thirteenth century found in the teaching Christ the subject for its greatest works; the fifteenth century saw in God the Man of Sorrows. The Passion had always been at the center of the Christian faith, but formerly the death of Christ had been a dogma that addressed itself to the intellect. Now it was a moving image that spoke to the heart." There was a return in the windows of Norfolk and York to the depiction of such elaborate group subjects as the "Last Supper" and the "Entry into Jerusalem," and an increasing interest in the depiction of individual rather than generalized types; the ruddy flesh tint of earlier periods was abandoned in favor of a pure white, which gives the otherwise intimate figures a curious spectral quality. In the south of England the treatment of the figure remained somewhat more hieratic, as in the "Virgin and Child" in the east window of Merton College Chapel, Oxford, and the portraits of Edward IV and his consort in Canterbury; the essentially linear style had already partially given way to an extremely sensitive tonal modeling. But beyond such works as these neither the medieval conception of man nor the art of stained glass could be extended.
The conquest of naturalism, the development of easel painting to the level of a fine art, and the subjugation of all other media except sculpture to the role of minor arts were the proud, and at the same time tragic, achievements of the next two centuries. There was in 16th-century stained glass at its best a kind of robust athleticism; at its worst, an indifferent aping of Raphael and Michelangelo. The leading was no longer treated as an integral part of the design but was regarded as nothing but a structurally necessary evil. The more purely pictorial the design became, the more alien and obtrusive the leading became, overemphasizing in haphazard fashion certain contours of the subject matter and altogether abandoning others, as can be seen in the "Triumph of David." The smoothly rendered modeling of the effects of light and shade gave the glass a dull parchment-like appearance; and the ability to make larger and flatter, more evenly colored, and less textured pieces of glass than in the Middle Ages was also exploited to the detriment of the art. This, along with the introduction of translucent colored enamels, finally reduced the art to such travesties as Sir Joshua Reynolds's "Virtues" in the New College Chapel, Oxford. In these windows Reynolds got rid of the leads completely, only to have his armatures become "prison bars," which, when they deign to bend with a knee or elbow, seem positively fatuous.
From the mid-16th century until the mid-19th century there was scarcely a thing in stained glass that was not slavishly derived from easel painting or the graphic arts, little that had not been far more easily and excellently achieved in these other media. The revival of the art that has since taken place may be divided into four distinct though overlapping phases.
First, there was the rediscovery, analysis, and restoration of the ancient windows, which may be placed roughly in the three decades from 1840 to 1870. In England Charles Winston, a lawyer by profession, became enamored with medieval stained glass and proceeded during the 1840s and 1850s to make a most thorough study of the succeeding styles, painting techniques, and types of glass used in English windows. From this labor of love came two still valuable books, his Hints on Glass Painting, which he published anonymously in 1847, and his Memoirs, which were published posthumously in 1865 (see bibliog.). Winston was among the first to recognize how inadequate the glass of the early 19th century was for stained-glass windows, and it was largely through his efforts in England that the manufacture of antique glass was revived. In France, Eugène Viollet-le-Duc supervised the restoration of several of France's greatest medieval structures, including Notre Dame in Paris, and published in 1868, in the ninth volume of his monumental Dictionnaire raisonné de l'architecture française, an article on stained glass that emphatically demonstrates the "logic" of medieval stained glass. Even though the theories in "Vitrail" have since come under criticism (see bibliog.), there is no question about the validity and timeliness of Viollet-le-Duc's essential point: "Different processes, different conditions, different branches of art…. In an opaque painting the radiation of the colorsis absolutely under the control of the painter, who … can diminish or augment it at will. The radiation of transparent colors in glass cannot be thus modified by the artist whose whole talent consists in profiting by it to work out a harmonic scheme on a single plane, like a rug."
Second, there was an increasing effort on the part of the makers of stained-glass windows to recapture some of the qualities of medieval stained glass, which began at about the same time and resulted, by the 1870s and 1880s, in the ability of the better studios to turn out technically competent but almost universally lifeless and sentimental neo-13th-, 15th-, and even 16th-century windows. This movement flourished with the great wave of architectural revivals that began in the Victorian period and was finally broken only by the Great Depression of the 1930s. The names of this movement are less the names of individual designers than of the studios that were founded or enlarged to meet the great demand for such stained glass—firms more or less competent in their ability to imitate the windows of earlier periods, more or less motivated by purely commercial interests.
Third, there was the periodic effort on the part of artists not initially trained as stained-glass designers to free the art from its bondage to historical styles and ineffectual variations on historical styles. This effort began very largely with two men, William Morris and Sir Edward Burne-Jones, who met as undergraduates at Oxford in 1853 and formed a lasting alliance based upon a common philosophy of art. Within the aesthetic limits of the pre-Raphaelite movement, Morris, with Burne-Jones as his chief designer, largely succeeded during the 1870s and 1880s in realizing his objectives. In the judgment of Sir Herbert Read, "his selection of colours is admirable, and he was not afraid of using colours to achieve effects unknown to previous ages. In the use of leads to emphasize design he is masterly, and we must again go back to the 13th century for an adequate comparison."
In America the artists John LaFarge and Louis Comfort Tiffany were leaders a generation later in the development of a distinctively American style, using an iridescent, milky, "opalescent" glass—a style that, especially in the case of Tiffany, was art nouveau in character and was employed not only in church windows but in secular settings of every conceivable kind. Tiffany was that rare combination, the consummate craftsman and the born entrepreneur, and he was among the comparatively few American artists of his time to achieve international recognition.
In Germany in the 1920s Jan Thorn-Prikker, Karl Schmidt-Rottluff, and Josef Albers (later moved to the U.S.); in Holland Joep Nicolas; and in Ireland Erie Hone began to create work of integrity; but the generally conservative architecture of that decade, followed by the worldwide Depression of the 1930s and then by World War II, all conspired to postpone the further development of stained glass for another 25 years.
The postwar period provided the indispensable conditions for the fourth and final phase in the revival of stained glass as a living art form: an experimental architecture capable of producing two such completely opposite yet equally masterful and original settings for stained glass as Dominikus Böhm's Church of Maria Königin in Cologne and Le Corbusier's Notre Dame du Haut in Ronchamp; the need to build buildings of every kind on an unprecedented scale; the willingness and ability of outstanding painters such as Fernand Léger, Henri Matisse, and Alfred Manessier to create stained-glass windows conceived purely in terms of the medium; and finally, talented younger men turning to stained glass as their principal medium of expression.
To achieve "a design of imaginative worth free from the cramping influence (and the mere imaginative insufficiency) of the craftsman, and a technical execution of this design free from the craft amateurishness of the imaginative artist" (Sir Herbert Read) was the goal that William Morris set for himself in mid-19th century; this goal has never been more achievable than in the mid-20th century.
Bibliography: theophilus, called also rugerus, On Divers Arts: The Treatise of Theophilus, ed. and tr. j. g. hawthorne and c. s. smith (Chicago 1963), thought to have been written between 1110 and 1140, contains the most complete medieval description of stained-glass techniques. c. winston, An Inquiry into the Difference of Style Observable in Ancient Glass Paintings, Especially in England: With Hints on Glass Painting (Oxford, Eng. 1847); Memoirs Illustrative of the Art of Glass-Painting (London 1865). e. viollet-le-duc, "Vitrail," Dictionnaire raisonné de l'architecture française du XI e au XVI e siècle, 10 v. (Paris 1854–68) 9:373–462, pub. serially in Eng. in Stained Glass 26–28 (1931–32). c. w. whall, Stained Glass Work (London 1931), still the most complete craft manual in Eng. c. j. connick, Adventures in Light and Color (New York 1937), lavish but dated elaboration on the theories of Viollet-Le-Duc, with some excellent color and light studies of medieval windows. j. r. johnson, The Radiance of Chartres (New York 1965). r. sowers, Stained Glass: An Architectural Art (New York 1965), more detailed exposition of material contained in first three sections of this article, illustrates approximately 50 French, German, and American windows created since 1955. m. aubert et al., Le Vitrail françis (Paris 1958). j. baker and a. lammer, English Stained Glass (New York 1960). g. marchini, Italian Stained Glass Windows (New York 1956). h. wentzel, Meisterwerke der Glasmalerei (Berlin 1954).
The technology for making glass dates back at least 5,000 years, and some form of stained glass was used in European Christian churches by the third or fourth century a.d. The art of stained glass flowered in the 12th century with the rise of the Gothic cathedral. Today only 10% of all stained glasses are used in churches and other religious buildings; the rest are used in residential and industrial architecture. Though stained glass has traditionally been used in windows, its use has expanded to lamp shades, Christmas ornaments, and even simple objects a hobbyist can make.
Stained glass has had various levels of popularity throughout history. The 12th and 13th centuries in Europe have been designated as the Golden Age of Stained Glass. However, during the Renaissance period, stained glass was replaced with painted glass, and by the 18th century it was rarely, if ever, used or made according to medieval methods. During the second half of the 19th century, European artists rediscovered how to design and work glass according to medieval principles, and large quantities of stained glass windows were made.
In America, the stained glass movement began with William Jay Bolton, who made his first window for a church in New York in 1843. But he was to be in the business for only six or seven years before returning to his native England. No other American practiced the art professionally until Louis Comfort Tiffany and John La Farge began working with stained glass near the end of the 19th century. In fact, the art of stained glass in the United States languished until the 1870s, and did not undergo a true revival until the turn of the century. At this time, American architects and glassmen journeyed to Europe to study medieval glass windows, returning to create similar art forms and new designs in their own studios.
A leaded stained glass window or other object is made of pieces of glass, held together by lead. The pieces of glass are about 1/8-inch (3.2 mm) thick and bound together by strips, called "cames" of grooved lead, soldered at the joints. The entire window is secured in the opening at regular intervals by metal saddle bars tied with wire and soldered to the leads and reinforced at greater intervals by tee-bars fitted into the masonry. A faceted glass panel differs slightly from traditional leaded stained glass in that it is made up of pieces of slab (dalle) glass approximately 8 inches square, or in large rectangular sizes, varying in thickness from 1-2 inches (2.5-5 cm). These slabs are not held together with lead; rather they are embedded in a matrix of concrete, epoxy, or plastic.
Glass is made by fusing together some form of silica such as sand, an alkali such as potash or soda, and lime or lead oxide. The color is produced by adding a metallic oxide to the raw materials.
Copper oxide, under different conditions, produces ruby, blue, or green colors in glass. Cobalt is usually used to produce most shades of blues. Green shades can also be obtained from the addition of chromium and iron oxide. Golden glass is sometimes colored with uranium, cadmium sulfide, or titanium, and there are fine selenium yellows as well as vermilions. Ruby colored glass is made by adding gold.
Stained glass is still made the same way it was back in the Middle Ages and comes in various forms. For the glass used in leaded glass windows, a lump of the molten glass is caught up at one end of a blow pipe, blown into a cylinder, cut, flattened and cooled. Artisans also vary this basic process in order to produce different effects. For example, "flashed glass" is made by dipping a ball of molten white glass into molten colored glass which, when blown and flattened, results in a less intense color because it will be white on one side and colored on the other.
So-called "Norman slabs" are made by blowing the molten glass into a mold in the shape of a four-sided bottle. The sides are cut apart and form slabs, thin at the edges and as much as 0.25 inch (0.6 cm) thik) at the center. Another form of glass, known as cathedral glass, is rolled into flat sheets. This results in a somewhat monotonous regularity of texture and thickness. Other similarly made glasses are referred to as marine antique, but have a more bubbly texture.
Processing the stained glass
- 1 Large manufacturers of stained glass mix the batch of raw materials, including alkaline fluxes and stabilizing agents, in huge mixers. The mix is then melted in a modern furnace at 2500°F (1371°C). Each ingredient must be carefully measured and weighed according to a calculated formula, in order to produce the appropriate color. For cathedral glass, the molten glass is ladled into a machine that rolls the glass into 1/8-inch (3.2
mm) thick sheets. The sheets are then cooled in a special furnace called an annealing lehr. The glass is then inspected, trimmed to standard size, and packed into cases.
At a typical factory, eight to ten different color runs are made per day. Some manufacturers cut a small rectangle of glass from each run in order to provide a sample of each color to their customers. There are hundreds of colors, tints, and patterns available, as well as a number of different textures of cathedral glass. Different textures are produced by changing the roller to one having the desired texture. Glass manufacturers are continuously introducing new colors and types of glass to meet the demands of their customers.
Creating the window pattern
- 2 Though some of the tools to make stained glass windows have been improved, the windows are still hand crafted as they were centuries ago. The first step of the process involves the artist creating a small scale version of the final design. After the design has been approved, the craftsperson takes measurements or templates of the actual window openings to create a pattern. This pattern is usually drawn on paper or cardboard and is the actual size of the spaces to be filled with glass.
Next a full-sized drawing called the cartoon is prepared in black and white. From the cartoon, the cutline and pattern drawings are made. The modern cutline drawing is a careful, exact tracing of the leadlines of the cartoon on heavy paper. The leadlines are the outlines of the shapes for patterns to which the glass is to be cut. This drawing serves as the guide for the subsequent placing and binding with lead of the many pieces of glass.
The pattern-drawing is a carbon copy of the cutline drawing. It is cut along the black or lead lines with double-bladed scissors or a knife which, as it passes through the middle of the black lines, simultaneously cuts away a narrow strip of paper, thus allowing sufficient space between the segment of glass for the core of the grooved lead. This core is the supporting wall between the upper and lower flanges of the lead.
Cutting and painting
- 3 Colored glass is then selected from the supply on hand. The pattern is placed on a piece of the desired color, and with a diamond or steel wheel, the glass is cut to the shape of the pattern. After the glass has been cut, the main outlines of the cartoon are painted on each piece of glass with special paint, called "vitrifiable" paint. This becomes glassy when heated. The painter might apply further paint to the glass in order to control the light and bring all the colors into closer harmony. During this painting process, the glass is held up to the light to simulate the same conditions in which the window will be seen. The painted pieces are fired in the kiln at least once to fuse the paint and glass.
Glazing and leading
- 4 The next step is glazing. The cutline drawing is spread out on a table and narrow strips of wood called laths are nailed down along two edges of the drawing to form a right angle. Long strips of grooved lead are placed along the inside of the laths. The piece of glass belonging in the angle is fitted into the grooves. A strip of narrow lead is fitted around the exposed edge or edges and the next required segment slipped into the groove on the other side of the narrow lead. This is continued until each piece has been inserted into the leads in its proper place according to the outline drawing beneath.
- 5 The many joints formed by the leading are then soldered on both sides and the entire window is waterproofed. After the completed window has been thoroughly inspected in the light, the sections are packed and shipped to their destination where they are installed and secured with reinforcing bars.
- 6 For faceted glass windows, the process begins the same way, with the cutline and pattern drawings being made with carbons in a similar manner. The pattern drawing is then cut to the actual size of the piece of glass with ordinary scissors since there is no core of lead to allow for. The thick glass slabs next are cut with a sharp double-edged hammer to the shape of the pattern. To give the slab an interesting texture, the worker then chips round depressions in the glass with the same hammer. This is called faceting.
Instead of glazing with lead, a matrix of concrete or epoxy is poured around the pieces of glass. The glass pieces have first been glued to the outline drawing, which is covered with a heavy coating of transparent grease so that the paper can be removed after the epoxy sets. The whole is enclosed within a wooden form, which is the exact size and shape of the section being made. The worker must wear gloves during this process, since epoxy resin is a toxic material. After hardening, the section is cleaned and cured prior to shipping and installation.
The process for making an entire stained glass window can take anywhere from seven to ten weeks, since everything must be done by hand. Cost can vary widely depending on complexity and size, though some windows can be created for a cost as low as $500. The customer can choose an existing pattern rather than create an entirely new one to minimize costs. In this case, the pattern can be customized by altering shapes or by changing the placement of the central image.
In the last 20 years there has been an explosion in growth of glass studios in the United States and it appears this growth will continue. For instance, in Ohio alone the number of studios has increased from a mere half a dozen to at least 100. The Stained Glass Association of America membership includes 500 studio owners and 300 manufacturers. The circulation of its quarterly publication totals 6,000. There has been a resurgence in restoration overseas, and the home market continues to grow. The hobby market also appears strong, with one publication serving this market having a circulation of 15,000. It is clear that stained glass is now recognized as a true art form no matter where it is used, and innovative designs using this medium will continue to flourish.
Where To Learn More
Clark, Willene B. The Stained Glass Art of William Jay Bolton. Syracuse University Press, 1992.
Clarke, Brian, ed. Architectural Stained Glass. McGraw-Hill, 1979.
Plowright, Terrance. Stained Glass Inspirations and Designs. Kangaroo Press, Australia, distributed by Seven Hills Book Distributors, 1993.
Achilees, Rolf and Neal A. Vogel. Stained Glass in Houses of Worship. Inspired Partnerships Inc. and the National Trust for Historic Preservation, 1785 Massachusetts Avenue NW, Washington, DC 20036.
The Story of Stained Glass, 1984. The Stained Glass Association of America, PO Box 22642, Kansas City, MO 64113. 800-888-7422,816-333-6690.
—Laurel M. Sheppard
A. S. Hargreaves