LedBoots, ha! This is great. I was secretly hoping that someone would be afraid of lye. This gives me a chance to geek-out in soap talk. Ok, so here's a lesson, if you have time and interest enough to read it:
Lye is an old generic term that refers to any strongly alkaline solution. For soap making, we use sodium hydroxide to make bar soap and potassium hydroxide to make liquid soap.
The process is this for bar soap: Mix the sodium hydroxide with water. It heats up to 200 degrees Fahrenheit by itself. If you touch it at this point, you get a chemical burn and a temperature burn at the same time! In the meantime, you mix all your oils together and heat them to 100 degrees. When your lye-water cools down to 100 degrees, you mix it all together. The sodium hydroxide reacts chemically with the oils in a process called saponification. By the way, when you look at an ingredients list and see something like "saponified coconut oil," that just means that it's coconut oil that has combined with lye, and if you see "Sodium coconate" or any other "Sodium ***" ingredient, that means that it's an oil combined with sodium hydroxide. Different ways of saying the same thing, and if you want to be cynical, you could say that it's two different ways of avoiding the word "lye" or "sodium hydroxide" in your ingredients list. Anyway, this saponification reaction happens, and the final result is a combination of soap, leftover oils, and glycerin. The sodium hydroxide has been all used up in the process and should no longer exist in the soap.
That being said, to get that happen properly, we measure our ingredients very specifically so that we don't put in too much lye, and we add extra oil just to be sure that there is plenty of oil for the lye to react with. And then we let it cure for 6 weeks, which allows water to evaporate, hardening the bars. After that, we do a pH test on the batch. A proper pH level is about 10. If it's more alkaline then that, then that might mean that too much sodium hydroxide was used, and it didn't all get used up, which is bad. In that case, the soap is unsellable. But I've never seen that happen. It's a safe process as long as each ingredient is measured very specifically.
So here's the thing with Grandma's soap: Back in the day, they didn't have the internet and digital scales. They had recipe books and measuring cups. It was easy to have a recipe that was a little off or a measurement that was a little off, which could result in a little too much sodium hydroxide being used, and such a "lye-heavy" bar could be a bit painful. Now, we have the luxury of websites that tell you very, very specifically how much lye to use for a given recipe, and we have digital scales that weigh it all out very precisely. And on top of that, we have the pH strips to verify the safety of the bars. It's a different world.
I'm such a soap geek. Thanks for letting me do that. The important things to remember are that every (and I mean every) product that calls itself "soap" was made with some form of lye (as required by law), even if the ingredients don't indicate that, and also that lye in it's raw form is dangerous, but in a finished bar of soap, it should be non-existent. So don't be afraid of lye. Use gloves and goggles if you ever make soap, and don't worry about it otherwise.
While I'm at it, a couple things just occurred to me:
1) Some soap makers use "melt-and-pour" soap. This is just a method where you buy soap that's already made, and then you melt it, mix some scents and colors in it, and let it cool and harden in a mold. You can get such a thing at your local hobby store. Some of those soap makers will then tell you that their soap wasn't made with lye. They are mistaken. The truth is that the soap that they bought from the hobby store was made with lye at a factory somewhere before they bought it.
2) Sodium Tallowate is an important ingredient to know if you're a vegan. It's animal fat that's been combined with sodium hydroxide. It's the number one ingredient in most store-bought soaps. It's generally fat from a pig, cow, or sheep. It's a low-cost ingredient that produces a hard bar of soap, so non-vegan soap companies love it.
Ok. I'm done geeking out, unless anyone has a question, in which case I can geek out again!