I posted this on thedishforum: On the German soapmaking forum, there are several posts noting that there seems to be a correlation between ash and oxidation of oils. Can you speak to the presence of ash and soap going rancid? And got this reply: Yes, I could see this being an accurate observation. Rancidity is an oxidative process. When fatty acids oxidize, some of the products of those reactions are aldehydes and ketones. Aldehydes with fewer than 6 carbons, in particular, will form soluble carboxylic acid salts when treated with sodium hydroxide (lye). Because of their solubility, those salts are probably some of the precipitates that form when soap ashes. This might explain an observed correlation between rancidity and ash. Additionally, saturated fats, in particular, can form crystals under certain conditions (grains in butters, anyone?). Because they lack the reactive double bonds needed for tight crosslinking during polymerization into the soap colloid, they sometimes precipitate out, and because of their solubility when converted to soap, can migrate out of the soap as water moves to the surface. This happens in in old oil paintings, for example. http://cool.conservation-us.org/waac/wn/wn...1/wn20-108.html [Broken] The trick is to identify what those conditions are, that cause crystal formation. I might dig into the chemistry of this further, after New Year's, when I have time to go peruse the chemistry library. I have limited access to articles from home. I'm quite sure that commercial soap manufactures know *exactly* what causes efflorescence, and how to prevent it. Could someone spell out what happens to the oils in the soap, and the soap itself, when soda ash develops? If soda ash is possibly a sign that the soap is going bad, then preventing soda ash is more important than many who make soap believe. Thanks very much for your help!