Painting Using Egg Yolk Rather Than Oil
Puzzle 13 of The Moon Hard Pack
Question is: Painting Using Egg Yolk Rather Than Oil
and the answer is: TEMPERA
Word Meaning:
TEMPERA — (uncountable) A paint in which the pigments are suspended in a water-soluble emulsion, such as of egg yolk or gelatine, which hardens and becomes insoluble on exposure to air.
Definitions from Wiktionary.