Why Renaissance Masters Added Egg Yolk to Their Paints: A New Study Sheds Light

Today we think of the Renais­sance as one of those peri­ods when every­thing changed, and if the best-known arti­facts of the time are any­thing to go by, noth­ing changed quite so much as art. This is reflect­ed in obvi­ous aes­thet­ic dif­fer­ences between the works of the Renais­sance and those cre­at­ed before, as well as in less obvi­ous tech­ni­cal ones. Egg yolk-based tem­pera paints, for exam­ple, had been in use since the time of the ancient Egyp­tians, but in the fif­teenth cen­tu­ry they were replaced by oil paints. When chem­i­cal analy­sis of the work of cer­tain Renais­sance mas­ters revealed traces of egg, they were assumed to be the result of chance con­t­a­m­i­na­tion.

Now, thanks to a recent study led by chem­i­cal engi­neer Ophélie Ran­quet of the Karl­sruhe Insti­tute of Tech­nol­o­gy, we have rea­son to believe that painters like Bot­ti­cel­li and Leonar­do kept eggs in the mix delib­er­ate­ly. Oil replaced tem­pera because “it cre­ates more vivid col­ors and smoother col­or tran­si­tions,” writes Smithsonian.com’s Tere­sa Nowakows­ki.

“It also dries slow­ly, so it can be used for longer after the ini­tial prepa­ra­tion.” But “the col­ors dark­en more eas­i­ly over time, and the paint is more sus­cep­ti­ble to dam­age from light expo­sure. It also has a ten­den­cy to wrin­kle as it dries,” vis­i­ble in Leonar­do’s Madon­na of the Car­na­tion below.

Putting in a bit of egg yolk may have been a way of using oil’s advan­tages while min­i­miz­ing its dis­ad­van­tages. Ran­quet and her col­lab­o­ra­tors test­ed this idea by doing it them­selves, re-cre­at­ing two pig­ments used dur­ing the Renais­sance, both with egg and with­out. “In the may­olike blend” pro­duced by the for­mer method, writes Sci­ence­News’ Jude Cole­man, “the yolk cre­at­ed stur­dy links between pig­ment par­ti­cles, result­ing in stiffer paint. Such con­sis­ten­cy would have been ide­al for tech­niques like impas­to, a raised, thick style that adds tex­ture to art. Egg addi­tions also could have reduced wrin­kling by cre­at­ing a firmer paint con­sis­ten­cy,” though the paint itself would take longer to dry.

In prac­tice, Renais­sance painters seem to have exper­i­ment­ed with dif­fer­ent pro­por­tions of oil and egg, and so dis­cov­ered that each had its own strengths for ren­der­ing dif­fer­ent ele­ments of an image. Hyper­al­ler­gic’s Tay­lor Michael writes that in The Lamen­ta­tion Over the Dead Christ, seen up top, “Bot­ti­cel­li paint­ed Christ, Mary Mag­da­lene, and the Vir­gin, among oth­ers, with tem­pera, and the back­ground stone and fore­ground­ing grass with oil.” Thanks to the oxi­diza­tion-slow­ing effects of phos­pho­lipids and antiox­i­dants in the yolk — as sci­en­tif­ic research has since proven — they’ve all come through the past five cen­turies look­ing hard­ly worse for wear.

Relat­ed con­tent:

How Car­avag­gio Paint­ed: A Re-Cre­ation of the Great Master’s Process

Dis­cov­er Harvard’s Col­lec­tion of 2,500 Pig­ments: Pre­serv­ing the World’s Rare, Won­der­ful Col­ors

The Largest & Most Detailed Pho­to­graph of Rembrandt’s The Night Watch Is Now Online: Zoom In & See Every Brush Stroke

A 900-Page Pre-Pan­tone Guide to Col­or from 1692: A Com­plete High-Res­o­lu­tion Dig­i­tal Scan

A 3,000-Year-Old Painter’s Palette from Ancient Egypt, with Traces of the Orig­i­nal Col­ors Still In It

The Old­est Known Globe to Depict the New World Was Engraved on an Ostrich Egg, Maybe by Leonar­do da Vin­ci (1504)

Based in Seoul, Col­in Marshall writes and broad­casts on cities, lan­guage, and cul­ture. His projects include the Sub­stack newslet­ter Books on Cities, the book The State­less City: a Walk through 21st-Cen­tu­ry Los Ange­les and the video series The City in Cin­e­ma. Fol­low him on Twit­ter at @colinmarshall or on Face­book.