Making Soap from Wood Ash (Potash) and Oils, Part 3

      Most websites say that the lye solution is the correct strength when a small potato or raw egg floats while showing an amount above the surface tension of the water about the size of a quarter. Most sources are unclear about the proper pH of lye water, but it is expected to be somewhere between 13 and 14 (the most alkalotic substances known to man) to be strong enough to saponify oils.
     It is difficult to guesstimate an approximate recipe to use the lye water. One person states, "If your lye water will float an egg with only a quarter size showing, boil down 1 gallon of lye water to 3/8 cup. Use 2 cup fats with 3/4 c. concentrated lye water…proceed slowly adding small amounts lye to fats whipping briskly each time."
     Another recipe concerning the proportion to ash water to fats can be found here. The author states, "Thirty-five liters of ashes is about the right amount for 2 kilograms of fat (a bushel of ashes for 4 pounds of fat). This proportion is cited in soap-making recipes of the colonial period in the United States, but many of the recipes of that era differ on the proportion of ashes to fat. Put 115 ml (1/2 cup) of lye in the kettle for every 230 ml (1 cup) of fats or oils."
     Another soap making website says the ratio of home-made lye water to fats should be "115 ml (1/2 cup) of lye in the kettle for every 230 ml (1 cup) of fats or oils." It goes on to say the mixture should be boiled until it becomes thick, foamy, and rubbery.
     This site has a surprisingly well-written article about how to neutralize an alkalotic pH in liquid soaps. In short, boric acid or borax is added to the soap solution, then allowed to precipitate, leaving the remaining soap more neutral and clear. Of course, proper pH testing is necessary to prevent skin reaction (we can handle more acid than alkali). Adding more fat will also bind the alkali in the lye.

Making Soap from Wood Ash (Potash) and Oils, Part 2

     On the other hand, Mother Earth News has printed an article from 1972 that says this about making wood ash lye at home:

To make lye in the kitchen, boil the ashes from a hardwood fire (soft woods are too resinous to mix with fat) in a little soft water, rain water is best, for about half an hour. Allow the ashes to settle to the bottom of the pan and then skim the liquid lye off the top. You can do this daily and when you've got enough of the weak solution, start the soap making process by boiling the liquid down until it'll float an egg. Now put that meat fat, left-over cooking lard and vegetable oil into a kettle not over half full, and heat the whole mess until all the liquid has been rendered out of the solid scraps. While it's still hot, add this clean grease to the bubbling lye and continue to boil the mixture, stirring all the while, until it reaches the consistency of thick cornmeal mush. 

     The article goes on to say that added salt makes the soap set into bars more easily, and that non-hardwood ashes are too resinous to produce soap. That last statement could use a good skeptical questioning, since pine tar soap is renowned for its anti-inflammatory properties against ailments such as psoriasis.