lye questions

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kinipela

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I am making home made lye from ash. The problem i have is i do not know how much of it to use in the recipe. For example if a recipe calls for 4 oz of crystals how much do i use of the lye solution i make from the ash. Any help would be great.
 

DeeAnna

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You can't make soap with wood-ash lye (potash, potassium carbonate) in the same way that you make modern "cold process" type soap with sodium hydroxide. For one thing, the potash lye is not as efficient at saponifying as a hydroxide lye. For another, you typically won't accurately know the alkalinity of the wood ash lye and how efficiently any given wood-ash lye solution will act -- too many impurities, too many variables.

You will have to use the classic trial-and-error boiled method. This means you add some lye solution to the fats, heat-stir-saponify for some time, check for lye heaviness (zap), add more fat or more lye depending on the zap test results, and so forth. When your soap is "fitted", meaning it has a slight zappy-ness that doesn't change with continued heating and stirring, then you'll have your final product -- a soft paste soap.

If you want a harder soap at the cost of having less soap overall, you will have to salt out the paste. That will convert some of the potassium soap to sodium soap and will alter the solubility of that soap in the water phase. Simmer to allow the sodium soap to form curds, float, and separate from the water phase, remove and either discard or reuse the "niger" (the water phase), and then mold up the soap. It may never be as hard as modern bar soap, because you will not get a 100% conversion from potassium soap to sodium soap.

Have fun!

ETA: This topic comes up regularly. See also http://www.soapmakingforum.com/showthread.php?t=44951 and http://www.soapmakingforum.com/showthread.php?t=56235
 
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