My first ever exposure to lye was seeing Edward Norton's character's skin bubble and burn in Fight Club after Brad Pitt's character threw powdered lye onto it. I never could have predicted then that I would someday be working with that substance myself on a regular basis and even - of all things - writing a blog post on how this stuff is actually A-OK to create an out-of-this-world bar of soap!
There's a number of folks out there who struggle with the idea of a soap made with lye (listed as sodium hydroxide on our labels). Some can even recall the days when a grandparent stirred a pot of hot, raw soap themselves; this was generally a combination of leftover fats and oils from cooking and meat processing that met with lye (the super traditionalists would even create their own lye from wood ashes). Soap has been made this way for a very long time - even the ruins of Pompeii revealed a soapmaking factory along with finished bars of soap used to prepare textiles for weaving! Soap created in this manner was usually, as you can imagine, a very inaccurate process - particularly if you were creating your own lye solution. Many ended up with very lye-heavy, soft, greasy soaps that were very harsh to the skin, sometimes it would even burn to the touch!
How is handmade soap today different? Very simply, we know more about the chemistry behind soapmaking, we have pure grade lye, and we formulate to be on the side of moisturizing with a lot more accuracy than ever before. Now bear in mind that I am not a chemistry major, and I'm going to try to present how soap is made as simply and accessibly as possible. Ready to find out what happens with all those ingredients on the label? Good!
First, it is important to keep in mind that without lye, there cannot be soap. It is simply impossible. There are some soapmakers who shy away from discussing lye (or they'll mislead about it altogether - yikes!), but I feel it is up to us in this craft to educate our customers about lye and to make it a little less scary for you. I must also mention that there is a type of soap called "melt and pour" soap, which is a block of premade soap base that crafters can (as the name implies) melt, modify, and pour to create an array of designs. Does this soap base require lye? If it is true soap, then the answer is always yes. The difference is that the process of turning fats and lye into soap has already occurred and these crafters don't need to handle lye themselves (which is very appealing for those who don't want to handle caustic chemicals or want to involve their children in this as a crafty project). Here at OHTC, we create our own soap using fats and a lye solution instead of using a premade melt and pour base. There are also cleansing bars out there comprised of a mix of SLS detergents and other chemicals to create a product that looks like soap. For the purposes of this discussion, it is not soap in its true form, which is an alkali salt of fatty acids. (What the what? Read on!)
Ready for some chemistry? Very simply put, true soap is created when you mix together acids (fats, oils) with an alkali (sodium or potassium hydroxide - depending on whether you make liquid or solid soap) that has been dissolved in a liquid (water, milk, tea, coffee, etc) to create a solution. When these fats are combined with the lye solution, a chemical reaction occurs between the lye and the fats that produces heat, glycerin, and what chemistry recognizes as a salt (we call it soap!). Creating these recipes require a lot of math and double-checking to make sure that you have enough fat to react with the lye solution - in fact, most soapmakers include what we call a "superfat" into our equation. We purposefully put more fats in than the lye can possibly react with, which ensures that our finished soap is moisturizing, mild and not at all lye-heavy. This is all measured as accurately as possible, which means measuring by weight (never volume!) and using a digital scale.
We also cure our soaps for a period of time to ensure mildness and to allow our bars to become firm and long-lasting in the tub! Here at OHTC, all of our soaps are cured a minimum of 4-6 weeks (most of the time, it is a full 6 weeks of curing!). This allows the liquid that was in the lye solution to evaporate out of the bar (making the soap much firmer) and the soap actually continues to react and saponify further during that time (ensuring a mild final product).
But - why is sodium hydroxide on the label? FDA labeling requirements for soapmakers can go one of two ways: we either list what goes into our soap pot or what comes out. To ensure accuracy, we list what goes into our soap pot instead of the finished result, which is why you find sodium hydroxide (lye) listed on our labels. We must list our ingredients in order of prominence and without the appropriate lab testing required to determine the exact amounts of glycerin, leftover unsaponified butters and oils, we cannot determine the order that these ingredients should be in with any degree of accuracy. So in order to stay FDA compliant and to be as accurate as possible, we list our ingredients as "what went into the pot" to create our finished soap. The exact butters, oils and fats used and in what amounts they are used in is what makes each recipe (and each soapmaker) a unique one!
A word for soapmakers and soapmakers-to-be: these soap recipes are often created over a long period of time and with a lot of investment in order to find a final master formulation. The formula I use at OHTC was over 4 years in the making in order to have a finished soap that is long-lasting, bubbly, moisturizing, and still leaves you clean as a whistle! I haven't even told my own husband my entire formula! Most of the soapmakers I know are incredibly protective of their trade secrets. If you're considering going down this path, please don't let that discourage you. There are many basic soap formulas available on the internet (always double-check these with a lye calculator!). Once you've become comfortable with the process of soapmaking, experimenting and developing a formula for yourself is an incredibly valuable process that teaches so much!
Another valuable game-changing aspect to modern soapmaking is that we also now have pure, food-grade lye that our forebears did not have; yet another way to be very accurate with our lye-to-fats ratio. Did you catch that I said "food-grade" too? This doesn't mean that you can eat lye directly (yikes no!) but it does mean that the lye is pure enough to use in cooking. Just like with soapmaking, even though lye isn't present in the final product, it is used in cooking to help create an innocuous final product. Soft pretzels, olives, hominy, canned mandarin oranges, Japanese ramen noodles - all of this is made using food-grade lye! Lye is also used to modify the pH of other products due to its extremely alkaline nature. Other examples of products which contain lye are: toothpaste, hair dyes, facial moisturizers, eye liners, aftershave, baby wipes, lipsticks, breath fresheners, baby lotion, and even eye drops! (source:
Good Guide)
Now a word of caution. I don't want anyone to come away from this post thinking that lye in its pure form is completely safe. It isn't. It is a highly caustic substance - so much so that it is often used to clear drains and clean ovens. Those products contain a never-ending list of warnings and caution symbols for a good reason! Unless otherwise stated, products which contain lye for these purposes are not pure, 100% lye that can be used for soapmaking and they are definitely not the products that we use to create our soaps! Even when using our 100% pure food-grade lye, responsible soapmakers must wear a lot of safety equipment in order to be well-protected from our lye solutions while we are creating our soaps.
I hope that I have helped explain that lye, when used responsibly, can be used to create a fabulous and mild end product, like hand crafted soap, and it shouldn't be the thing keeping you from trying a bar!
