Knitting the Light Fantastic

Knitting, spinning, dyeing and other crafty goodness

Making Soap – Part 1: Fun with Lye

Posted by notthatkat on August 22, 2007

I threatened you with a tutorial on making soap, and even though no one specifically asked for it, I’m posting one anyway. Why? Because I want to, and I recently made another batch (cold process), and actually took pictures.

Danger Will Robinson! Knitting content has left the building for the duration. Consider yourself warned. The next few posts will be long and picture intensive and have nothing to do with knitting.

The most important thing to consider when making soap is safety, safety, SAFETY. Lye (or another strong base) is a necessary ingredient in making soap. While there is no lye present in the final bars, the process of making soap involves handling a chemical that will burn skin, eyes, etc. on contact. You shouldn’t be afraid, but you should respect the potential for injury. I have made a lot of soap, and I’ve never had a major problem, but I credit that, at least partially, to using good common sense and some basic safety equipment:

Safety Equipment

I wear gloves and safety glasses through the entire soap making process. I use basic latex gloves, but I’ve seen the rubber kitchen/cleaning gloves used. I use safety glasses as on the top left, but goggles such as are on the top right are also an option. The mask, I don’t use consistently (why I don’t further down), but others consider it very important, and some use a respirator instead.

Fire Extinguisher

A fire extinguisher is always a good idea, although fire risk is minimal with cold process soap.

Vinegar Bath

Finally, I make up a solution that’s about half water and half vinegar with a bit of dish soap thrown in. This is good to have on hand in case of accidental contact with lye or caustic soap, and I throw my utensils in when I’m done with them to neutralize.

So, once I have my safety equipment lined up and my work surface covered in newspaper (makes cleanup super easy), my next step is mold preparation

Prepared Mold

Lots of items make good soap molds, as long as they are not porous and can handle a bit of heat. I’ve not had much success in using fancy detailed molds with cold processed soap. It is still fairly soft when unmolding a day or two later; I never tried leaving it in the mold longer, but I think such molds are best left for melt and pour. My favorite molds are simple wooden boxes I put together myself. The one above is the smaller of the two I’ve made. I line these molds with freezer paper, with the plastic side to the inside, folded to fit the mold and the overhang taped down. I like small Glad Ware style containers for small (test) batches, usually about a pound. But this is my mold of choice for larger batches.

Soap is made by the reaction between a strong base (lye) and the fatty acids of fats. Many types of fats can and have been used. Tallow (rendered beef fat) and lard are the traditional animal fats for soap making. I use a combination of vegetable oils as my primary base, although some animal products like beeswax and milk can enhance a soap recipe tremendously.

I always run my soap recipe through a lye calculator, whether it’s one I’ve made up or someone else’s. I’ve seen published formulations with too much or too little lye and the results are not good either way. The first lye calculator I ever used is still my favorite, but good ones can also be found here and here. These are all provided by soap suppliers that I’ve been very pleased with, BTW.

The next step is to measure out the lye and water and mix them. If you haven’t already, this is when you need to put on glasses and gloves (and mask or respirator if you prefer)

Lye and Water

All of the base ingredients for soap except water, should be measured by weight, and you need a scale accurate enough to give you a fair bit of precision for the size batch you are preparing. I use a postal scale that measures up to 11 pounds, and is accurate to a tenth of an ounce or a gram (I use the same one for weighing yarn and fiber and dyeing). I still have a bit of the Red Devil lye that I stocked up before it got pulled from all the store shelves. Once it runs out, I hope to find a chemical supply house within a reasonable driving distance. Otherwise I will have to suck it up and pay hazmat fees, in which case, I will probably buy in bulk quantities. Stupid meth-heads.

For water I use distilled water as the mineral content and treatments of tap water can lead to problems in both the reaction and final product. It is the one ingredient that precise measurement is not critical and a range of volumes can be used. It is primarily a vehicle to get the lye into a liquid state where it can react with the oil. Too much water yields a very soft soap that may have problems getting out of the mold. My formulation called for 10-15 ounces and I used 12 ounces (about 180 mL for those of you on metric)

Next we are going to mix our lye into our water:

Add Lye to Water

Important Safety Note #1 – Always, always add the lye to the water. Never do it the other way around.

Important Safety Note #2 – This process will give off fumes which are very irritating and bad to breathe in. I always do it outside and keep my face away from the container. I don’t have a problem that way, and don’t notice a difference with or without the mask. I’ve not used a respirator, but this is why some people advocate using one. If you mix them inside, make sure you are in a well ventilated area (on the stove, with the exhaust fan running would be a good choice). If you’re outside, make sure you’re upwind.

Important Safety Note #3 – This solution will get very hot (close to boiling) Be sure to use a heat safe container. I use a Pyrex measuring cup, but I’ve also used stainless steel bowls.

Mixing lye

Stir the mixture, keeping your face well away from the container (awkward stirring at arm’s length, but best if you can manage) The solution will get cloudy, and the lye may cake on the bottom, which feels gritty against the spoon. Mix until the lye is all dissolved, then let it sit.

Clear Lye solution

Once the lye solution is clear, it is no longer giving off fumes and is safe to bring back inside. The container is still hot, so be careful. By the time I got the container back inside and measured temperature, it was still about 175 degrees Fahrenheit.

Hot Lye

This seems like a good breaking point, so I’ll stop here for now. Hopefully, I haven’t lost too many of you. Up next – kitchen chemistry in action.


2 Responses to “Making Soap – Part 1: Fun with Lye”

  1. susan said

    Okay you have my attention. Never made soap but I will read any tutorial with good pictures and great explanations. You have both. Can’t wait to see the end product.

  2. Michelle said

    What a great tutorial on using lye. I like the visual.

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