burning pot

Making lye soap

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We were doing a history project, I must have been in Grade 7 or 8. My partner Mark and I were supposed to make lye soap. We quickly decided that making the lye by leaching wood ash would take too long. The only reference we had said something about "weeks".

Wood ash had other problems:
- How much ash do you need?
- What do you put the ash in for leaching?
- Do you leach the same water through several times to make it stronger?
- Lye comes as a powder. Do you have to dry it out or are you really aiming to get a liquid equivalent to the lye/water mix?

No, I don't know the answers!

So we started with dry lye. We needed to mix it with water, and add grease. I think we used lard, because it was commonly used in the pioneer community in Canada, and because it is easily available. But first we needed to mix the lye into the water.

We asked the teacher for a large pot, large enough to hold a gallon of water, with room to add the fat and stir it. He was really busy, since there were another 10 or 15 pairs working on projects and asking him questions. He took us to a kitchen next to the gymnasium, a room I'd never been in before, and handed us a big pot, about three gallons, and told us not to drop it, because the lye was dangerous if you spilled it on your skin.

We got our large wooden spoon, a tin of lye, and the lard, and put them all out on the counter. We measured a gallon of water, (that's an Imperial Gallon, about 4.5 litres or 1.25 US gallons, do you really care?) and put it into the pot. Then we added the lye, reached for the wooden spoon to stir it, and ... and ... it didn't need stirring! It was bubbling and foaming and filled half the pot, and got really hot. After about 30 seconds it was still bubbling strongly and smelled. I'm not sure now, but I think it smelled like rotten eggs.

Then the foaming liquid spilled out through the bottom of the pot and down over the edge of the counter, and across the counter. Nobody told us that you you can't put lye in an aluminum pot, at least not for long! Lye eats alumninum for breakfast!

If I remember correctly, the lye didn't hurt the counter top, or the tile floor, although it cleaned them really well. Our teacher showed us how to clean it up without burning ourselves, and another day we made one small cake of soap in a steel pot.


Do you want to make lye soap?

Since I put this story up on my web site, I have been asked several times for advice on making lye soap. Some of those questions came from people who clearly did not understand how dangerous and corrosive lye can be. And no, I don't have a recipe for making soap.

First, let me make one thing clear: Lye mixed with water (such as sweat on your skin) forms a powerful corrosive liquid and can severely harm people and property.

Disclaimer: I haven't made lye soap for over 30 years, and I was a teenager at the time. If you use my suggestions, it is at your own risk. I am not responsible for anything that happens to you. This includes, but is not limited to, the following illustrative examples. For instance, I am not responsible if:
- you buy a pot that is supposed to be stainless steel and it dissolves,
- lye discolors your mother's favorite roasting pan, or
- you or your residence get splashed by corrosive liquids.

Now that I have said that, I can make some comments that you may find useful.

What is it?

Lye is not an acid, it is the opposite: an alkali, but it is just as corrosive as battery acid. Acid, such as vinegar or cola, tends to neutralize it, but vinegar and cola are quite weak, and it would take a lot, like a quart, to neutralize a tablespoon of lye. Water dilutes it, making it less corrosive.

Lye reacts with some metals, such as aluminum. "Reacts" in this case, means it will dissolve it. I don't think it reacts with iron or steel.

Like a strong acid, I think lye reacts with plastics - and dissolves them. I wouldn't try putting plastic in lye, because I don't know enough about chemistry to be able to predict what gases might be produced. The gases produced could possibly be dangerous or even lethal. (Let me explain something that most people know: Lethal means "can kill people".)

Safety

Wear clothes you don't care about, with an apron or other extra layer you can easily and quickly take off in case of splashes, without getting it on your face and hands.

Have a lot of cold water handy, like a full sink or full pail, to put your hands or face in, in case of splashes. If you get a splash on you, even a small one, vigorously splash the spot for about a minute, to dilute the lye.

Perhaps you could mix a test quantity, say 50 ml or 2 ounces of water with the appropriate amount of lye, in the container you want to use, and watch it for half an hour, outside on a lawn or sidewalk - with a lid on most of the time. There's no need to add the fat for the test.

Mix the test batch outside. Do NOT mix it in your kitchen, then carry it outside. Lye will burn through a thin aluminum pot in seconds.

If it dissolves a hole in the container, pour on a quart of vinegar to neutralize it, then dilute it with lots of water. The small sample quantity will not harm the environment if it escapes, especially when it's neutralized with vinegar. The concentrated lye might kill the grass in a small area (instantly). The lid will keep wildlife out. You will be there to notice if it gets out of the container.

The container

Use a container you don't care about. Used steel cooking pots are available in second hand shops for a couple of bucks. Cheap new cooking pots may cost about $10 or $20 depending on size. I think iron or steel is safe, so a large steel cooking pot should work. Ceramic or pottery containers should work, but a glaze may be severely damaged or removed completely by the lye. Perhaps you could make your own in pottery class.

Make sure the container is twice the volume of the liquid you want to mix, including all ingredients. You don't want it to splash outside the pot when you are stirring. I know it bubbles at first and gets hot. I think it may spit. Make sure it has a lid.

Of course aluminum (and plastic) will dissolve and leave you with a horrible mess, as I found in school.

Apparently some sources recommend that a container for making lye soap should be dishwasher safe. A dishwasher safe container is not necessarily safe to put lye in. Dishwasher safe merely means it will probably not be damaged by the boiling heat generated as you mix the lye with the water. For example, aluminum pots are dishwasher safe, but not lye safe.

Mixing tools

Use a wooden spoon.

Where to buy lye

I don't know what store in your area would carry it. I would start by asking in a hardware store. The brand I used was "Gillet's Lye". I'm not sure of the spelling.

Final comment

I welcome comments from people who have actually made lye soap recently. In particular, does anybody think I am over reacting here?
 
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