Lye used to be available in the supermarket but not anymore. You might be able to find it in some hardware stores often in the drain cleaning section next to the Draino. In order for that lye to be effective in soapmaking, you need to make sure that you are getting 100 percent sodium hydroxide. Otherwise, do not buy it.
If you can't find lye for soapmaking locally, do not worry there are plenty of online stores where you can get it. Going with an experienced vendor selling lye specifically for the soapmaking trade is the safest, and believe it or not, usually, the cheapest way to go. Lye is also used for food curing, candlemaking, dehairing hides, cleaning out drains, and beekeepers use it for cleaning out old hives.
Check your local hardware store. Lowe's hardware stores sell Roebic Crystal Drain Opener. According to the product label, it is 100 percent lye. It is available in a two-pound container and can be found at all Lowes stores.
The common lye product formerly known as Red Devil was discontinued many years ago due to its frequent use in the illicit production of meth or methamphetamine.
If you look online, you're guaranteed to find high-quality, pure lye that's appropriate for soap making, and you can buy it in whatever quantity you want from the following stores:
Chemical Supply Company
Get together with other soap makers in your area and go together and buy a large bag of lye from a local chemical supply house. Lots of soap makers buy their lye in bulk. Most large cities have a solvent or chemical company that will sell sodium hydroxide in 35- or 50-pound bags. You'll pay a fraction (per pound) of what commercial products cost, but, you will need to safely store that much lye. It needs to be stored in an airtight container, safely away from children, pets, or other unknowing people.
Make Your Own
Lye is the commonly used word for sodium hydroxide (NaOH) or potassium hydroxide (KOH). Both compounds are strong alkali, highly soluble in water, and they produce caustic base solutions. Although the potassium compound is more appropriately called potash instead of lye, it is often confused for the sodium compound. It is supplied in various forms such as flakes, pellets, microbeads, coarse powder, or a solution. Both potassium hydroxide and sodium hydroxide are usable in making soap, but the potassium compound lends itself to liquid soap meanwhile the sodium compound will render a more solid, bar soap.
Before people could get their hands on processed sodium hydroxide, they had to make lye the old fashioned way by leaching water through wood ashes layered in a barrel or some other container. The result was primarily a soft, gooey soap. Wood ashes have a tendency to produce mostly potassium hydroxide.
History of Lye
The ancient use of lye for soapmaking and as a detergent is actually found in the ancient origin of the English word, which came from the earliest form of the Germanic word, laugo, and ultimately from the Proto-Indo-European root word leue-, "to wash." Relatives in other Germanic languages, besides their words for lye, include the Nordic words for Saturday (laugardagur in Icelandic and lordag in Swedish, Danish, and Norwegian) meaning "washing day."