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Lye calculator program


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millersoap.com is legendary here. Most people are using the online calculators like http://www.soapcalc.net/calc/SoapCalcwp.asp. You might like that one. What you're missing mainly is knowing the strength of your homemade lye solution.

Actually, I think I have that figured out. The old timers used to float an egg or potato in their solution. If an area about the size of a quarter showed above the water, the solution was the right strength.

I doubt they'd ever heard the term 'specific gravity', but that's what it amounts to. So an older recipe that calls for ( just an example) 38 oz. of water and one can of lye, should come out pretty close if I use 50 oz of the lye solution. 38 oz. of water + 12oz. of lye.

The older recipes I've found are all based around a 12oz can of lye. Apparently that's the only size it used to come in. Most of them call for around 35 or 40 ounces of water. I'm guessing that the egg/potato trick is gonna give you just a tad over a 3 to 1 ratio of water to lye.

My thinking is that I could make the solution just a little stronger. Just to be sure.

Then maybe add a little salt at trace to kill some of the excess lye? Or 'wash' with a makeshift saline solution made from salt water?

Of course I could be full of shit. Wouldn't be the first time.

And the links were just things I ran across... thought they could be useful to someone. If I'm gonna ask a bunch of stupid questions, I'll at least try to put something back. :)

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All I know about salt in this process is that it's used industrially to separate glycerin from the soap. Maybe it can be useful in other ways, but did the old timers use it? If you do stuff they wouldn't do, then you might as well use a hygrometer instead of a potato, or titrate the lye solution to find out exactly what you've got.

Probably there was always trial and error involved, with people achieving consistent results as they gained experience with their lye and soapmaking techniques. In your shoes I'd try to keep it as simple as possible. Use your best guess about the lye concentration to make a small batch of soap and see if it's caustic or greasy, then adjust.

I reckon people got mighty dirty in the old days, plus they used the soap for laundering as well as washing. They might have liked it pretty strong. For your purposes you might want to emulate the modern handcrafters and aim to discount the lye a little. You could get away with as much as 10% residual oil in a lard soap and have it work just fine. 3-5% would be just perfect.

In those recipes you mention, the lye is by weight and the water presumably by volume. Did you come up with your equivalencies by figuring out the density of the solution produced by the potato test and calculating the KOH content from that?

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OK. I hit about 100 websites this weekend and I'm still sorting and trying to parse all that info. Bear with me if I'm talking out my butt.

Someone in the other thread mentioned making a batch that was lye heavy and doing a saline wash. That niggled something in the back of my little pea brain. I finally remembered hearing my grandparents say something about dipping their soap in brine, to leach out lye when they had too much in it.

I'm thinking that making it lye heavy could be fixed. The PH could be brought back into balance. If the PH is off in the other direction, it would be almost impossible to fix. At least with my level of know how.

Also, with measurements, the whole thing here is a modern person dumped into relatively primitive surroundings. He'd have about the same knowledge as I do. Maybe heard the grandparents talking, saw a demonstration at some state park and/or saw something about it on the history channel. He wouldn't have a set of scales or a hygrometer. He might be able to find an egg, though. He'd also be reduced to having to measure out ingredients with coconut shells, or some such. THis person won't have our ancestors' experience, but he'll have the advantage of high school chem class to help make up for it.

Also, a fluid oz of water generally weighs around 1.04 oz by weight. This could vary a bit, depending on how much crap is in the water. Pure rainwater should be at or below that 1.04 figure.

Now I'm figuring that I would do this a bit water heavy and a bit lye heavy, since I think I could fix both of these problems after the fact. A brine bath should neutralize left over lye, as well as leaching out some of the water, through osmosis. This would be done after the soap had cured enough to be demolded. Better, still if you could cut it into bars, then dip it, I'd think.

Frustrating thing is that I can't try any of this out, because I live in an apartment building. They might get a bit testy if I started manufacturing lye in the court yard. :shocked2:

Trust me, if I still lived in the country, I'd have run off a batch or 10 this weekend, instead of bugging everyone with a bunch of stupid questions. I'd much rather be doing it than typing about it.

If you see any holes in my logic, feel free to speak up. All input is appreciated.

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Well, the one thing in your reasoning that doesn't sound right is that its better to be long than short on lye.

Getting the pH of the soap correct isn't the objective. You can be 5% short on lye or 10% short without affecting the pH of the soap at all. Being short on lye doesn't pose a problem unless you're very short. In fact, a little discount makes the best soap.

Upon full saponification of the oils, the pH the soap hits a minimum in the ballpark of 9.5, so all soap is about the same pH unless there's free caustic in it. That's the main thing to avoid, and it's easier to avoid it than to fix it. People here generally rebatch when that happens, melting down the soap and adding some oil.

Finals thoughts: The amount of water isn't critical - you have some leeway there. The critical part of the recipe is the dry weight of KOH vs. the weight of oil. If you want to calculate the right proportions rather than figure it out experimentally, the only clue you have for the amount of KOH you're using is the density of the lye solution. Your procedure has to include a method of measuring that in some way, shape or form that stays within your rules.

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I could be wrong but what I was thinking is that if you go too short on the lye, you won't get saponification. No saponification and the batch is ruined. All your materials are then wasted.

Is that a correct assessment?

If that's correct and you don't have enough materials available for another batch, then you'd kind of be screwed.

If that isn't correct, the rest of my conclusions are out the window. ( In this case, that would be a good thing.):)

And I hear what you're saying about getting accurate measurements. This isn't possible in this case.

That's why I was thinking to err on the lye heavy side. If my above assessment is correct, then this would be the only way to be sure that I wound up with soap, rather than a tub full of useless goo. Even if that soap was short of perfect and needed fixing or rebatching.

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Not enough lye and your soap won't saponify. Many people make an all coconut oil soap with a 20% superfat. That means that 20% of the oil is unsaponified after the soap is cured. It's supposed to make a nice soap, I haven't tried it.

If you make a soap and it is even 1% too much lye, it will make it very uncomfortable to use. Itchy and/or burning at the least and it could damage your skin at higher percentages. You're better off going short on the lye.

Whatcha makin'? Soap with lye from ashes?

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Whatcha makin'? Soap with lye from ashes?

Yeah. It's just a stupid story that I mentioned here and in the coconut milk thread. Kind of a Giligan's Island type thing. I think I figured out enough to make the story work, about 2 days ago. Now I'm just mostly trying to solve the puzzle, I guess.

I tend to be way more curious than is good for me.

I think the guy in the story is just gonna get real lucky on the measurements and it's all gonna work just right, the first time. :D

I just didn't want to get yelled at too much.

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The oil will saponify until all the caustic is used up. If you're short on lye there will be residual oil, which is considered desirable for handcrafted soap. We normally calculate a 3 to 5% lye discount for our batches and you can discount more than that. You would have to be way short to end up with useless goo. But as Carrie points out, just 1% long and you'll have something that most nowadays would consider useless -- and it's hard to fix.

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The oil will saponify until all the caustic is used up.


That's where I was screwing up, then. :rolleyes2

Thanks a LOT.

I knew if you were that adamant, I must have been missing something. I just didn't know what and didn't know enough to figure out how to ask properly.

Thanks for bearing with me.

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