My parents found this book somewhere, and I really like what’s in it, the eggs are beautiful, and some of them very different. Something that is of interest to us is a small section on dyes that includes the information and photos of eggs dyed with natural dyes. What is of special interest, is the wood ash mordant that she used with great results. See yourself in the photos below.
Apparently wood ash was used as a mordant as well as a dye: