Friday, October 17, 2008

Heather recently gave us a lovely product review on her blog, and in the comments on that blog, she got a variation on that age-old question - "Why do they use lye to make soap? Isn't lye a toxic substance?".

This is a very, VERY common question that we get asked. Anyone who makes or sells handmade soap will invariably get asked this question. Heather did not know the answer to that question, so she asked us. We LOVE when customers ask questions!!! We wrote her a response, which she put on her blog (with our express permission). Because this is such a commonly asked question, I thought we'd put the answer here as well.


Let's start with the very basics. You cannot make soap without lye. Soap is
made by a chemical reaction occuring between fats (oils) and lye (sodium
hydroxide, or other similar alkaline substance....but we won't diverge into
that just now). The phrase "chemical reaction" is very important there - in
other words, those 2 ingredients, combine together and than CHANGE, to form
soap. Properly made soap, while made WITH lye, will not have any lye in it
at the end of the process. You will have saponified oils - also known as
soap. A quick check at your local library on any current cold process
soapmaking book will confirm those facts, as will this well-respected
soapmaking site:

Yes, Lye is a substance that must be treated with much respect. Improperly
used, it can be quite dangerous. However, used with care, caution, and
respect, it will turn ordinary oils into divine handmade soap that is very
good for your skin! As a point of fact, lye is also used to cure certain
types of food, such as lutefisk, hominy, and green olives. For more
information, you may visit this page:

There are many way to label soap -all falling within the letter of the law,
but some that "hide" the lye more than others. We believe in educating the
public, therefore we have "sodium hydroxide" listed right in the ingredients
list. Other soaps will have labels that say things like: "Saponified oils of
coconut, palm kernel, and olive", or list ingredients as "sodium tallowate"
or "sodium cocoate" (translation: saponified tallow, and saponified coconut
oil). These labels are technically correct - and still point to the same
process - lye combined with oils to create soap.

Liquid soap is handmade with a slightly different type of lye - Potassium
hydroxide, instead of sodium hydroxide ( or sometimes a combination of
both). The above facts remain the same, however - To make any soap, liquid
or bar, fats/oils must be combined with lye, and saponification then

Melt and pour soap is a quite different product - it is often comprised of
synthetic detergents, and we do not consider it a handmade product. Most
commercial liquid bodywashes are also quite full of synthetic sudsing
agents, colorants, petroleum-by-products and goodness knows what else -
frankly, we don't even consider them in the same realm as handmade soaps. We
personally prefer good handmade soap, made with lye, to artificial
ingredients we cannot pronounce. But to each their own!! :)


kim said...

I hope you can help me or push me in the right direction. I wanted to try to make my own soap 2 weeks ago, I got all the ingredients and (i thought) the right pans. The pan I had the oil in was stainless steel but i am sorry to say the pan i had the lye in was club aluminum so when i added the lye and water together it made a mess I was lucky to have had it in the sink. I finished the process, the soap has one more week to cure but I am wondering now if I should throw it away and try again (with stainless) could the lye have leached out aluminum and ruined the batch?

Anonymous said...

My question is, do you make your own lye? That is, it factory-made "sodium hydroxide"? Or is it good, old-fashioned lye made from hardwood ashes and water?

gadgetwoman said...

Kim: Throw the soap out. Do not EVER use Sodium Hydroxide (Lye) with anything aluminum...even stirring spoons. Since you mixed up the lye in an aluminum pan it will leach into your soap. I would consider the resulting soap unsafe to use.

For the next batch, use either Stainless Steel or heavy duty plastic. You can pick up a plastic pitcher at any "mart" of your choice for a few bucks. Label it prominently with the word LYE and don't use it for food.

Karla the Soaplady.

gadgetwoman said...

Veritybrown: I use factory made Lye in my soap for a consistent quality product.

Old-fashioned lye made by leaching water through hardwood ashes is inconsistent at best. Why do you think that Grandma's soap was so harsh? The strength of the lye would vary from batch to batch. She had to just guess on the strength of the solution,
how much to use per pound of fat etc.
This is one glaring example of how "modern conveniences" make a superior product.
Karla the Soaplady