Teach Soap

There's no hot process subforum, so this is where I'm putting these questions. If it belongs elsewhere, please, someone move it appropriately.

Some of you know that I participate in a living history group. I've not made any firm decisions about doing this, but I would like to make at least a few batches of soap in ways that were possible before the year 1600 CE. That means, for starters, making my own lye from wood ash. I know how to do this, at least in theory, and more than one of the homes I'm investigating is equipped with a wood-burning fireplace, so I'll have access to ashes (yay!).

The thing that worries me is determining how strong that homemade lye is, by methods that were available to the average soap maker within that medieval-and-prior time period. The usual method I've found in research is to float an egg in the lye. If it won't float, the lye is too weak. If it floats high in the solution, it's too strong. The objective is to float the egg so that just a little bit of it shows (roughly the size of a US 25-cent piece above the water). However, to my mind, that is not nearly precise enough.

Now, I've heard that there's a method of making hot process soap whereby the excess lye falls to the bottom of the boiling pot, leaving 0% superfatted soap at the top -- no excess lye, no excess oil -- to be skimmed off and put into the molds. My thought is to do that, skim off the soap, and then go back and add 3% to 7% additional oils for their skin conditioning properties. However, I can't find any directions for making that happen: what chemical to add to the soap, what temperature to reach, or anything like that, that would make the saponified oils reject the excess lye as a precipitate. It's probably something really simple, given that it's ancient technology, but I've been unable to find a source I trust on the matter.

So that's my question: What can I do to a batch of soap, of uncertain lye strength, to make sure that excess lye is removed from the batch?

My mother made soap from wood ashes. Since it's potassium hydroxide not sodium hydroxide it won't make a hard bar of soap. There is no way to know how strong your lye solution is. The floating egg is only a VERY rough estimate. The solution strength also depends on what type of wood was used to make the ash. You can salt out the rough, lye heavy soap so it separates into soap and lye water, but you won't know how much extra oil to add so the soap won't be lye heavy.

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Irena
Closed minds are like faulty parachutes; they refuse to open.

I've had the same dreams of making my own lye, but going the route of superfatting for skin conditioning properties seems more like drawing information from the present. Early soaps were most useful in stripping wool of lanolin or other cleaning chores, and were seldom applied to ones body except under the prescription of a physician. From the practical standpoint of getting the most detergent bang for your buck using an excess of lye then salting it out would give you a harsh but serviceable cake of mushy soap.

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Just call me "Apo"

No; the soap that's left on the top could still be lye heavy and not at 0% superfat. The salt helps for the lye water and the soap to separate into two disctinct components. Salt does make for harder bar, but in this instance, since the ash is potassium hydroxide (used to make liquid soap), the soap will not be hard.

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Irena
Closed minds are like faulty parachutes; they refuse to open.

Not while maintaining safe levels of lye. You can make historically-documentable soap, but it's something that should never be used on the skin. My mother used lye heavy soap once not wanting to waste it for her laundry. It ate holes through fabric.

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Irena
Closed minds are like faulty parachutes; they refuse to open.

Isn't that why you add Borax or Boric Acid to act as a buffer for the lye? My understanding of making laundry soap was to make the soap 0% superfat or even slightly lye heavy, grate it and mix with water, then buffer with enough borax to make it no longer caustic. Of course that's off track from making historical soap.

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Just call me "Apo"

How long has African black soap been made? For a long time I'll bet. It makes a usable bar even though it's made from ash and shea.

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Irena
Closed minds are like faulty parachutes; they refuse to open.

The info you need may come from a place other than this forum. My advice is to contact a place called Olde Stubridge Village,located in Sturbridge Ma. this is a fully functional historical town and the workers actually reproduce EVERYTHING the way it was done way back when,candles from fat drippings, bread in brick ovens , curing there own meats right on the premises ect,they may be able to help you out,justa suggestion.

My grandmother made soap right after the yearly hog slaughter (this is in rural Appalachia), but I suspect none of my aunts will remember the process--except maybe the oldest, and she's 93! I have no idea if she made her own lye, but I can ask.

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Lesli Sagan
Avital's Apiaries
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Linda
I know the voices in my head aren't real, but they sure have some great ideas!