Making and using (wood-ash) lye crystals

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Sep 22, 2015
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Last year I tried my first batch of soap and turned out with a slightly saponified jar of lard, or so it appeared. I had trouble finding instructions that covered all my variables: esp. using homemade lye crystals and lard. Here are some questions I have:

I boiled my leachate from the woodash and rainwater down to brown crystals. My thought was it'd be easier to store than lye water. Was it a mistake to create the crystals instead of using the lye water directly? If crystals are ok, how do I know how much water to dissolve the crystals in? I tried to measure lye strength when dissolving the crystals with a hydrometer, but it seems like maybe that gave me weak lye? Is there a good way to test pH more precise-seeming than dissolving a feather or floating an egg? I do have pH papers but maybe that's overkill?

If you end up with greasy 'soap', what's the easiest way to salvage it, cook it with more lye water? And how can you guard against creating caustic soao when tweaking a supposedly balanced recipe like that?

What's the simplest DIY mold you can make?
Simplistic mould can be a cardboard box lined with (if you are in America) freezer paper. You can reinforce the sides to keep it from bowing outwards.

If you want to make a decent soap, I would forget the home-made lye. If having a usable soap of any quality at the end of it is just a plus, and it is more the means rather than the ends that you are interested in, then go for it
not giving up

The simple mold sounds just my speed....

As for giving up on homemade lye, no way! People did it for centuries, it can't be that hard. :) I'm sure I can figureout how to make usable soap, I just need a little guidance.
Usable, yes. Nice to use, maybe not so much. For a long time people walked everywhere and hunted with spears, but now we tend not to, unless it is the means that is important, not the ends.

But, if you are dead set on it, remember that they used to 'salt out' the mixture, which means that they added more and more of the lye water until it zapped them (too much lye) and then added salt water until all the soapy curds floated on top, stripped of all excess lye. Also, and here is the annoying part, it is stripped of all of the glycerine and superfat, leaving a soap that is not something I would want as a result of my efforts.

Not only that, but it will always be semi solid at best, as you are not using sodium hydroxide, so making bars of soap is going to be tricky to say the least.
Actually, I believe the lye you make from wood ash is more potassium hydroxide than sodium hydroxide, so you would make a liquid soap paste with this method at best. Sodium hydroxide (which makes a hard bar) was not reliably produced until the late 18th century, and even then, it was in a lab, not a kitchen.

If you're dead set on using historical techniques for soap-making, you might check out the Society for Creative Anachronism or other re-enactors' groups for more guidance. Remember that those who actually made the nice soaps that the weathy used for cleaning their bodies did so as a trade in which they trained exclusively from a young age for many years before their soaps were anywhere near good. The soaps made in kitchens on a regular basis were of the harsh variety and were generally intended for surfaces and cookware, not bodies.
Actually, wood ash lye is potassium CARBONATE with some amount of sodium carbonate, depending on what type of plants the ash comes from. But you are correct, TeaLeaves, that the soap from wood ash lye ends up being a potassium (soft) soap.

Because potassium soaps are highly soluble in water, including salt water, these primitive soaps are not generally salted out due to the high loss of soap that results. There are methods to change carbonate lye to a hydroxide lye, but not if you just have access to wood ash.

And, yes, HS, making a good soap IS a challenging task, and that is especially true if you use a wood ash lye. The technique is not the same as how modern soap is made, as The Gent has pointed out. That's why soap makers were one of the skilled trades in any town or city.
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Gent -- Historical soap making without soap calcs -- and current commercial methods even with soap calcs -- do the job of making soap by saponifying fat with an excess of lye and water -- the "boiled" soapmaking method. Even in the old days, soap makers had a pretty good idea of roughly how much lye was needed to saponify different types of fat and so were able to share general recipes for different types of soap, but the assumption in the recipes was the maker needed to tweak the total amount of lye and also the lye concentration as the situation required.

Once this type of saponification is done, how do you separate the soap from the excess water-phase liquid? A sodium soap is fairly soluble in nigre (the watery alkaline liquid left over from the "boiled" saponification process), but sodium soap is less soluble in salty water. That's where the process of salting out comes into play -- you're adjusting how much soap can remain dissolved in the watery liquid so when you separate the two, not as much of your soap ends up washing down the drain with the nigre.

Potassium soaps are highly soluble in salty or plain water, so they were/are generally not salted out -- you just lose too much soap down the drain. A potassium soap can be firmed up by adding some salt, but that's more akin to thickening a modern liquid (KOH) soap by adding salt -- and is not at all the same as salting out.

Commercial soap makers test the sap values of their fats to establish a starting point for their soap making, but they don't blindly rely on the sap values like we handcrafters do -- they don't assume that X grams of fat + Y grams of lye = soap. They saponify with an excess of lye, as the old makers did, and do lab tests of free alkalinity (not pH!) to verify the soap is fully saponified. The old makers checked whether the soap was done and reasonably low in excess alkalinity by using the time-honored zap test and evaluating the appearance of the soap in the soap pot and by looking at cooled samples on a ceramic or glass dish.

We handcrafters don't do all this because we don't have access to lab testing and the rather sophisticated training required to be an old fashioned expert soap boiler. We count on the sap value of the fats, the lye purity, etc. to be reasonably accurate and make soap based on the numbers. That's actually a rather risky approach, but it (usually) works fairly well. Making a "boiled" soap gets around the need for close accuracy -- you don't have to have as rigid control of lye purity and fat sap values. This information is important, but it is not as critical that it be as accurate as in handcrafted soap making.
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"...Is there a good way to test pH more precise-seeming than dissolving a feather or floating an egg?..."

Testing pH is not an accurate way to know the concentration of a lye solution. The pH scale is logarithmic, which means it requires a relatively large change in concentration to affect the pH. And once you're above a few percent of NaOH in solution, the pH actually changes very little. The only way to reliably and accurately know the alkalinity of the solution is to do an acid titration.

The old method of floating an egg is a test of the density of a liquid. Density is an indirect measure of the concentration of a solution if you know exactly the type of solution you're dealing with. You need to use the right age of egg because the air space within the egg needs to be a consistent volume to get reasonably okay results. Older eggs = larger air space.

Can't say much about the feather method, which is an indirect test of alkalinity -- you're on your own with that one.
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All preferences aside against doing things this way, if you were required to make woodash soap without sophisticating measuring methods, how would you determine the concentration/amount of lye water to use?

I know it won't be super quality, but I want something serviceable.
No modern measuring equipment? Then you're stuck with floating an egg. I'm not kidding or pulling your leg here -- that's the most reasonable low-tech solution.

Here is advice on the matter written by Monsieur Claud Joseph Geoffroy in 1742:

....An hydrostatical Balance, a Water-poise , and other Instruments might also give this Degree [of lye concentration]; but in the Country [these instruments] are not at hand, and I judged it best to point out only what is most easy.

Soapboilers use for this End a fresh Egg; if one half of it sinks into the Lye, they judge the latter to be of the first Strength [highest concentration] ...; if the Egg sinks in to Two-thirds, the Lye is called the Second [middle concentration]; and, lastly, if the Lye covers the whole Surface of the Egg, it will be called the First [lowest concentration], and will be that with which they begin their Operation or Boiling....
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After sleeping on it, I realized I forgot to explain that even Monsieur Claud in 1742 was working with a hydroxide lye made from reacting carbonate lye with lime. He wasn't just using the carbonate lye direct from the wood ashes.

And about the eggs -- store bought eggs can be only a few days to a week or three old. If you don't have access to fresh-from-the-hen eggs, that may skew your results.
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