[112] By the way, to capture such detail, Flemish artists mastered the use of oil-based paints. Until about 1500 an egg-based paint called "tempera" was what most European painters used. They'd mix the mineral-based colors with egg yolk which, when dried, became the binder.

[113] But then, Flemish painters begin using oil-based paints. With this new improved paint — the same mineral-based colors are mixed into vegetable oil. Now, when dried, the oil — rather than egg yolks — binds the color.

[114] This oil painting by the Flemish artist Jan van Eyck — from the early 1400s and still vivid — is exquisite in its detail. The Madonna's delicate face, the saint's robe, the weave of the carpet, the stubble on the aging face…glasses actually magnifying the print…are all possible because of the qualities of oil-based paints.

[115] Ever since, oil paints have been the standard. With these paints, artists enjoyed richer colors and more flexibility — they could apply layer upon translucent layer (called "glazes") to create ever-more subtle details. While medieval paintings, like this lovely Madonna by Giotto, are egg-based tempera on wood, you can see the advantage oil-based paints on canvas gave later artists. With oil, Raphael could get a fuller spectrum of colors and Leonardo could paint with more nuance.