Titian Danae with Nurse

The palette of Venetian Renaissance artists, from Giovanni Bellini to Jacopo Robusti, called Tintoretto, is admired for its sheer brilliance and grandiosity. These artists were part of a more extensive color industry that prospered in Venice. The industry comprised dyers, glassmakers, tailors, and decorators of furniture and ceramics that all employed bright colors. Within the industry of color emerged specialists—vendecolori—shopkeepers or color vendors. They offered an array of materials for the color industry, including raw materials to prepare pigments. They provided many imported colors in addition to ones prepared locally. Their commodities included pigments such as azurite, orpiment, and vermilion, among many other materials.

The vendecolori offered highly refined and purified colorants to a broad customer base. Venetian artists could acquire materials of all kinds; some intended for other trades but usable in oil painting. Among these were glass made for the glass industry in Venice and pigments used by manuscript illuminators. The availability of these materials at the vendecolori increased the range of colors available to artists, and the properties of these innovative materials facilitated experimentation with novel effects.

Giovanni Bellini was an innovative painter throughout his career. He adopted materials and colors that augmented and defined the Venetian palette, such as indigo, the arsenic pigments of orpiment and realgar, and the copious use of the deep green copper acetate.

Giovanni Bellini and Titian, The Feast of the Gods

Giovanni Bellini, The Feast of the Gods, 1514–1514, National Gallery of Art, Washington, D.C.

Until the end of the fifteenth century, the minerals orpiment and realgar were primarily used only by miniaturists. In the sixteenth century, they became popular in Venetian painting, so that G. P. Lomazzo remarked in his 1584 treatise, “burnt orpiment is the color of gold, and it is the alchemy of the Venetian painters.” Venetian artists such as Bellini used it abundantly in their paintings. In The Feast of the Gods, Bellini achieved the brilliant orange of Silenus’ robe using orpiment mixed with a transparent red lake pigment.

Giovanni Bellini and Titian, The Feast of the Gods, detail of Silenus

Detail of the Feast of the Gods with Silenus and his orange tunic of orpiment and red lake pigments.

One way Venetian artists developed bright coloring in their paintings was to apply multiple thin, translucent layers that blend color in luminous, vibrant ways. Lomazzo described it in his treatise as painting “transparently.” This method of color mixing relies on being able to paint translucently, smoothly, and thinly.

The transparent layers of paint, known today as glazes, rely greatly on achieving transparency which is antithetical to the opacity or hiding power of most pigments. To achieve great transparency, Venetian artists used ingredients not previously found in earlier paintings. Venetian artists’ innovative use of materials is more remarkable than previously imagined and more complex than the simple application of pigments in thin paint layers.

To suggest the hue of the hills on the horizon in the far distance in The Feast of the Gods, Bellini mixed a yellow glassy pigment with azurite to subtly change its hue. This mixture is a remarkable blend of complementary colors to adjust the hue. It represents an innovative use of materials to achieve Bellini’s expression of color. There was no stable orange on the early Renaissance palette that could be used safely mixed with the copper carbonate mineral azurite. Bellini could have used an orange-yellow lake pigment, but these typically fade rapidly. Realgar and orpiment, which Bellini used in this picture to paint Silenus’ orange tunic, react with the copper compounds. The pigment Bellini decided on is a yellow lead antimoniate glass. Bellini’s antimonial yellows are not the Naples yellow of the eighteenth century but the early use of “potter’s yellow.”

The wide range of materials available at the vendecolori suggests that artisans from multiple trades that used color went there to obtain their raw materials. The variety available in Venetian color shops prompted researchers Barbara Berrie and Louisa Matthew of the National Gallery of Art in Washington, D.C., to consider evidence of non-pigmentary materials in the painting practice of Venetian artists.

Lorenzo Lotto, St. Catherine, 1522, National Gallery of Art, Washington, D.C.

From prior studies, samples from several paintings by Venetian Renaissance artists were available. Among the paintings analyzed was St. Catherine by Lorenzo Lotto at the National Gallery of Art in Washington, D.C. St. Catherine’s gown is a glorious red, perhaps reminiscent of the color of expensive red cloth worn by some Venetian women at this time. A cross-section from the sleeve shows the complicated layering Lotto used to create this color. The cross-section shows a ground layer of gesso (calcium sulfate dihydrate) prepared with parchment glue, providing a smooth surface for painting, over which he applied multiple layers of paint. The first layers of paint are pinks prepared from a mixture of vermilion and lead white. Over these are layers of transparent red paint. Although it appears to be a thick homogeneous paint film, it is, in fact, many layers of thin glazes of paint—at least six layers. Their analysis revealed that the layers contain both madder and insect lake pigments.

Paint cross-section of the bottom edge of St Catherine

A paint cross-section of the bottom edge of St. Catherine's gown.

When Berrie and Mathew employed SEM-EDS to determine the composition of the paint, what they found was surprising. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) allow scientists to analyze paint without removing samples from the picture. They found an element associated with lake pigments, alumina, the traditional material used to prepare insoluble pigments from dyes known as from lakes. Unexpectedly, several of the layers of glazes contain small, rounded particles, about 4–8 microns in diameter. These particles consisted of very pure silica.

Silica indicates the presence of glass. Auxiliary materials in glass, for example, sodium and potassium fluxes or the stabilizers, calcium, and lead, are below detectable limits. Venetian glassmaking required pure silica, which was, in this period, provided by quartz pebbles from the Ticino River.

The presence of silica is unexpected, and this occurrence appears to be the first finding of this material used by Italian Renaissance painters as an extender to give body in oil paint.

Most importantly, silica and glass have refractive indexes (R.I. 1.4585 to 1.52) similar to linseed oil (R.I. 1.468); as a pigment extender, it appears transparent in oil paint. The innovative use of glass and silica in painting—a non-traditional material for Renaissance artists, allowed Venetian painters to achieve glorious colors in their pictures.


16th-Century Renaissance Pigments and Painting Techniques, National Gallery of Art, Retrieved from the web on May 10, 2022.

Giovanni Paolo Lomazzo (1584). Trattato dell'Arte de la Pittura. Milan. 1.

David Bull and Joyce Plesters (1990). “The Feast of the Gods: Conservation, Examination, and Interpretation.” Vol. 40, Studies in the History of Art Monograph Series II. Washington: National Gallery of Art, 59, 64–65, .

Barbara H. Berrie and Louisa C. Matthew (2005). “Material Innovation and Artistic Invention: New Materials and New Colors in Renaissance Venetian Paintings.” Scientific Examination of Art: Modern Techniques in Conservation and Analysis. Washington, DC: The National Academies Press. 12–26.

Barbara H. Berrie and Louisa C. Matthew (2006). “Venetian ‘Colore:’ Artists at the Intersection of Technology and History,” in Bellini, Giorgione, Titian and the Renaissance of Venetian Painting, exhibition catalog, eds. David Alan Brown and Sylvia Ferino-Pagden (Washington, D.C. and Vienna, 2006), 301–9.

Barbara H. Berrie (2015). “Mining for Color: New Blues, Yellows, and Translucent Paint,” Early Science and Medicine, 20(4-6), 308–334.

Optical constants of SiO2 (Silicon dioxide, Silica, Quartz): https://refractiveindex.info/?shelf=main&book=SiO2&page=Malitson

Oil Painting Materials Containing Glass