Blown glass vessels first appeared in Italy as early as 40 or 30 BC by Regia, the House of Livia, in Rome and other local glass workshops. Although these sites produced small glass bottles of various shapes, textures, and colors, they had yet to experiment with large glass artistic programs. The most significant innovation in the history of glassmaking was the discovery that glass could be blown, flattened into sheets, and separated into window panels with its durability and coloristic qualities still intact. Stained glass deals with the transmission of light through colored material where the laws governing light subject colored glass to its effects. Glaziers and painters aimed to evoke three-dimensional depth through color and contrast on ordinary sheet glass, where traditional fresco and tempera techniques proved insufficient. The glassworkers of these earlier periods needed to gain understanding of the relative values of tones that could change according to passing light and familiarity with the radiative qualities of certain colors that affected surrounding pieces of glass.
To produce glass, artists mixed silica sand, soda ash, and limestone among other natural elements in a furnace reaching 2552 degrees Fahrenheit. Using an iron blowpipe called a punty, the glassmaker gathered a ball of molten glass and rotated it constantly to prevent the glass from falling. The glassmaker carried the iron onto a stone slab called a marvel table where the artisan inserted a metal needle through the blowpipe to create an air pathway for the blowing process. Inflation required reheating the rod multiple times and maintaining the blow iron in a vertical position for further elongation. Once the glassmaker achieved the desired length by blowing, the vessel was chilled close to the nose and tapped sharply off the punty. The resulting cylinder was split down its length, reheated and flattened on a surface once ductile.
To color white glass, glaziers added precise amounts of metallic oxides. They pressed and rolled the molten glass onto the oxides on the marveling table. As a rule, glaziers worked with copper for deep green and red, cobalt for blue, manganese for purple, and iron for yellow. However, the coloring process required more precision than the addition of a handful of metallic oxides. The proportion of multiple coloring oxides and the amount of oxygen available to the elements in the furnace atmosphere produced specific shades, and glaziers needed experience to manipulate the chemical reactions that occurred between the elements.
Glaziers and painters worked together to create stained glass windows. Glaziers produced and melded the glass panels while painters provided detailed designs called cartoons on large sheets of paper, adding color notations. Glaziers assembled the glass pieces over the cartoon, scored the pieces accordingly, and carefully broke the glass along the desired lines. After cutting, the artisans assembled the pieces by inserting them into double-channeled lead strips called calmes and soldered the joints to compartmentalize the colors and ensure stability. Larger windows required additional support from iron bars which were embedded into the masonry of the building. Before installation, the artisan brushed the window and lead with a waterproofing compound made of linseed oil, whiting (chalk powder) and lampblack (a fine black pigment) for rigidity and protection, and then placed the stained glass panels into the prepared window frame.
Once a luxury item, glass became increasingly accessible throughout the Mediterranean world. Stained glass windows found their way onto the traceries of churches and monasteries by the 12th century and served as both visual storytelling tools and mediums for divine illumination. The first large-scale narrative stained glass campaign in the Upper church at Assisi was initiated by Pope Innocent around 1245. The colorful patterns and intricately woven narratives of stained glass windows brought to life the stories of the Bible, lives of saints, and moral lessons to worshippers and lay viewers alike, emerging as a transformative art form in medieval religious architecture.
Glass painters developed their art around the 14th century through new methods such as sticklighting and the painstaking technique. Sticklighting required dipping a piece of glass into black paint and scraping the dried paint off to create a design. The painstaking method used paint made of powdered glass iron oxide and water to add contouring and shading details.
Beyond the physical process, stained glass functioned as a dynamic art form, interacting with light and space to evoke spiritual meaning. Symbolically, stained glass windows represented the divine, created atmospheres charged with the presence of the sacred, and served as intermediators between earth and heaven.
By Celeste Silva-Carrillo
Bibliography:
Cheshire, Jim. “Stained Glass.”
Victorian Review, vol. 34, no. 1, 2008, pp. 71–75.
JSTOR,http://www.jstor.org/stable/41220402. Accessed 18 July 2025.
Cooper, Donal and Janet Robson.
The Making of Assisi. Connecticut: Yale University Press, 2023. Print
Grose, David F. “Early Blown Glass: The Western Evidence.”
Journal of Glass Studies,
vol. 19, 1977, pp. 9–29.
JSTOR, http://www.jstor.org/stable/24190598. Accessed 18 July 2025.
Hogan, James H. “Stained Glass.”
Journal of the Royal Society of Arts, vol. 88, no. 4560, 1940,
pp. 569–85.
JSTOR, http://www.jstor.org/stable/41359591. Accessed 18 July 2025.
Royce-Roll, Donald. “The Colors of Romanesque Stained Glass.”
Journal of Glass
Studies, vol. 36, 1994, pp. 71–80.
JSTOR, http://www.jstor.org/stable/24190054.
Accessed 18 July 2025.
Sculer, Frederic. “Ancient Glassmaking Techniques: The Blowing Process.”
Archaeology, vol. 12, no. 2, 1959, pp. 116–22.
JSTOR,
http://www.jstor.org/stable/41666510.
Accessed 18 July 2025.
Sears, Taber. “Stained Glass Windows.”
Art and Progress, vol. 3, no. 1, 1911, pp. 392–97.
JSTOR, http://www.jstor.org/stable/20560516. Accessed 18 July 2025
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Page: https://3d.wlu.edu/v21/pages/Orsanmichele/orsanmichele.html
Location of Annotation: -15.43, 64.67, 5.32
Camera Location: -15.159, 57.723, 6.845
Camera Looks Towards: -34.228, 96.840, 9.017
Annotation block name: The Production of Stained Glass Windows at Orsanmichele
Annotation Details:
The stained glass windows of Orsanmichele literally and figuratively revolve around the original miracle-working image of the Virgin Mary and Christ child displayed in the public granary in the heart of the city. The Madonna of Orsanmichele became the most accessible devotional image to lay citizens in Florence after 1284 and evolved from a common street tabernacle to a miracle-working cult image in 1292 to a city protector in 1365. Orsanmichele’s beautifully crafted windows celebrate the Madonna’s religious and civic significance to Florence and reflect the relationship between public images and Florentine viewers.
The glazing campaigns of Orsanmichele can be divided into three phases. The first glazing campaign, financed by the Confraternity of Orsanmichele, began shortly after 1380 and ran until about 1400; the second between 1400 and 1420; and the third lasted from 1429 and 1432. Financial difficulties throughout the process forced the confraternity to extend the execution of the tracery infills over a number of decades and request additional finances from the Signoria to cover the expense of stained glass. Original design was delegated to Simone di Francesco Talenti sometime before 1366 and Niccolò di Piero Tedesco served as master glazier for the first program. Niccolò di Piero Tedesco directed the second program and welcomed Lorenzo Monaco as the designer of the second campaign between 1400 and 1420. A Pisan merchant arranged for the production of two stained-glass windows above the two western portals in 1413. Glazier Francesco di Giovanni Lastra worked on the stained-glass windows with his partner Bernardo di Francesco in the last glazing campaign. Scholars identified artists such as Agnolo Gaddi and Ambrogio di Baldeses among other unknown designers.
Changes in master glaziers, the artistic idiosyncrasies of assistant glassworkers, as well as design development throughout the campaigns affected the decorative, technical, and compositional choices of each bay. A total of sixteen stained glass narrative panels exploring the miracles of the Virgin decorate Orsanmichele today, with twelve located in the four East bays nearest the Tabernacle and Altar of St. Anne as the earliest program. The first two bays on the north side and the first two bays on the south side each have only one narrative panel. Attention to detail, texture, coloristic display and heavy patterning, often at the expense of narrative clarity, characterize the original panels while the remaining four focus on architectural and spatial accuracy. The panels located closest to the Altar and Tabernacle emphasize the luminous and coloristic qualities of stained glass by displaying an overall multicolored approach where complementary colors juxtapose and create a melding dazzle of tones and textures. Glaziers utilized red-purple and blue-purple in large amounts to experiment with the textural possibilities of the medium and chose to employ elaborate embellishments through border and foliate decoration in the eye and rose windows.
Orsanmichele’s stained glass program reinforced the Madonna’s central role in Florentine myth and ritual and represented the spiritual fervor that spurred the construction and beautification of the once-former civic grain market turned devotional hub.
By Celeste Silva-Carrillo
Bibliography
Zervas, Diane Finiello. “Lorenzo Monaco, Lorenzo Ghiberti, and Orsanmichele: Part I.” The
Burlington Magazine, vol. 133, no. 1064, 1991, pp. 748–59. JSTOR, http://www.jstor.org/stable/884819. Accessed 28 July 2025.
Zervas, Diane Finiello. “Lorenzo Monaco, Lorenzo Ghiberti and Orsanmichele: Part II.” The
Burlington Magazine, vol. 133, no. 1065, 1991, pp. 812–19. JSTOR, http://www.jstor.org/stable/885060. Accessed 28 July 2025.
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