My display for Atlantian KASF 2024 was on using eggs as a way to measure the strength of lye water.
For modern soap making, you just buy lye that comes at a known strength and use soap making calculators to determine how much to use. But medieval soap makers passing water through wood ash would get lye water of unknown strength. Several medieval recipes call for using a fresh egg to determine if the lye water was strong enough.
This leads to many questions. Does the size of the egg matter? How fresh do the eggs need to be? What strength of lye water is needed to float an egg, and how does that compare to modern soap making lye strengths? I have chickens so I have a source of fresh eggs.
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