What type of paint uses egg yolk as a binder?

The type of paint that uses egg yolk as a binder is tempera, specifically egg tempera.

Traditional egg tempera is made by mixing powdered pigment with egg yolk diluted in water. The yolk binds the pigment into a paint that dries quickly and forms a durable, relatively hard film. Artists historically prepared it in small batches because the mixture was perishable and difficult to store.

Tempera has a long history in European religious and panel painting. Before oil painting became dominant in parts of Europe, artists used egg tempera for icons, devotional panels, and finely detailed images. Its fast drying encouraged controlled brushwork and layering rather than the slow blending associated with oil.

“Tempera” is a broad term, so not every paint sold under that name contains egg. Casein tempera uses milk protein, while some modern products use synthetic binders. School “tempera” paint may actually be a water-based poster paint with gums or starches.

Gouache is opaque watercolor, acrylic uses an acrylic polymer, and oil paint uses drying oils. Those binders make the alternatives incorrect for this question.