Which ingredient is a key component in classic tempera paint formulation?

The yolk of fresh hen's eggs is a key component in classic tempera paint formulation because it acts as a binding agent for the pigment. Traditional tempera paint, particularly the type used during the Renaissance, is crafted using dry pigments mixed with an aqueous emulsion from egg yolk. This emulsion provides the necessary adhesion to the substrate, resulting in a paint that dries quickly and has a matte finish. The natural properties of egg yolk allow the paint to maintain its color vibrancy while offering a certain level of flexibility and durability once dried.

Other ingredients listed, such as linseed oil, are more characteristic of oil-based paints, while watercolor medium is specifically formulated for watercolors, which have a different binding and application process. Glycerin is often associated with other mediums but is not traditionally used in the formulation of tempera. Thus, the yolk of fresh hen's eggs is fundamentally significant in making classic tempera paint.