Soap is a dichotomy in that it is so stupid easy it forms by accident and so complicated that you have to be very careful when you make it on purpose. At its most basic, soap is fat that is exposed to water and an alkaline substance. This causes a chemical reaction that changes the fat into soap.
Many plants contain saponins, which are soap LIKE in that they often foam and cleanse, but they are not actually soap. To create soap, the fat MUST be exposed to an alkaline substance like lye. Lye (sodium hydroxide) is so easy to make you can do it on accident. To make a really weak lye solution (which makes a fine soap) it is just water run through wood ashes. That is really it. A good rain after a forest fire and you have a weak alkaline solution. Our ancestors used to run water through wood ashes repeatedly until and egg floated in it. They used it to both tan animal hides and make soap.
Remember when I said it forms by accident? There are documented cases of “Soap Mummies” that form when alkaline water drips through the remains of a person. It becomes a substance called “adipocere.” You can read about an example here: http://archaeologynewsnetwork.blogspot.com/2011/01/mummy-made-of-soap.html
Much of what you buy in the stores as “soap” is not. During WWII, fats and oils were in very short supply. Soap became scarce. Through the magic of chemistry, a replacement for soap was created: detergent. With a little more tinkering, detergent bars were created to replace soap. What you buy in the store (way more often than not) is a detergent bar. It is bad for your skin, dries it out, and has a lot of harsh chemicals in it. Don’t use it on your hair unless you like it really screwed up.
Real soap is great for your skin and hair. It doesn’t leave build up (so you don’t need clarifiers) and leaves your keratin (skin and hair) shiny and clean without stripping away all of your natural oils. The entire beauty and hair industry is shaped around undoing the damage caused by these industrial detergents. That’s right. You are spending a fortune to repair the damage caused by the stuff you are spending a fortune on.
Modern soaps are made with refined lye or potash (Potassium hydroxide, or KOH) another alkaline inorganic chemical. Lye and KOH are alkaline or base chemicals. They can cause serious burns just touching your bare organic skin. The burns are worse than acid, actually.
Lye is used to make some foods (like pretzels) so it isn’t all that difficult to get food grade lye. If you plan on washing your face with it, please use food grade. Too many people use “privy cleaner” or “drain cleaner” to make soap and the soap seems inferior. The results just aren’t as good because there are other chemicals in the alkaline product.
We are going to turn our attention now to types of soap. First differences are bars and liquid. Liquid soap is made with Potassium Hydroxide, KOH. There are a few softer soaps in bar form made with KOH and I have seen at least one person use it to make glycerin soap. Soap made with KOH will not harden. It might evaporate into a soft waxy like substance, but it will never be mistaken for the bar soaps.
Bar soaps are made with sodium hydroxide, or lye. There are two major types: the traditional lye soap and glycerin soaps. Glycerin can be plant or animal in nature and creates a soft soap. The great thing about it is that after you create it, you can melt and reform it. It is an extremely liquid soap when melted which takes color and molds very easy. It is often sold in a “finished’ form in craft stores as melt and pour soap blocks. Melt and pour glycerin soap is the gateway to soap addiction. Anyone can use it, get great products and there is little danger in its use.
Traditional soaps made with lye are processed in three major methods; hot process, cold process and room temperature process. They each have their pros and cons.
HOT PROCESS: if the most dangerous, involved and makes an admittedly ugly soap. You can’t really mold it, you can’t do decorative pouring and you have to stand over it for a few ours. The pros are that the fats in the hot process soap never go rancid (even if you “superfat” it by adding more fat than you need to process the lye; the extra fat moisturizes the skin), it never gets chalky, the scents are much stronger, it lathers better and you can use the (its soft for about a month) soap right away. You also never have to worry about undissolved lye pockets.
COLD PROCESS: Is a much less maker dangerous soap to make. Rather than standing over it cooking it, you melt the fats and mix the ingredients cold, counting on the heat of the lye (it gets super hot when it comes into contact with water or organics) to “cook” the soap. It isn’t entirely cold, you have to melt the harder fats like Shea, or Cocoa butter (raw versions of those are very hard at room temperature). You can get very creative with the soap because it is liquid when you pour it; it can be molded or poured to make fantastic patterns The cons are that this type of soap is MUCH more likely to go rancid, it can take months to make, the scents are not very strong, and there is a risk of pockets of lye that don’t dissolve. You can burn someone with this soap if it doesn’t dissolve right. Also, you have to wrap it with heavy blankets and put it someplace to “cook” for a month, then cut it and give it another month or so to cure. I am just not a fan of this process.
ROOM TEMPERATURE: This method uses only fats that are liquid at room temperature. You cannot superfat the soap because the measurements have to be EXACT. The oils are prepared prior to the lye solution and are at room temperature. There is no melting of anything. The only heat that is applied is from the lye solution (which is often in excess of 200 degree F). It is pretty much like cold processing from here and again can be super creative in the molding and pouring. This has the same problems as cold process, just bigger. The scent oil is added at the beginning so the fragrance is weak, they can sweat things like calcium carbonate or weak KOH, and they can have pockets of lye solution in them because you don’t actively saponify the soap, time and its own heat to creates the saponification.
I know that a lot of creative people LOVE the Cold Process and Room Temperature process techniques for the artistic aspects. I’m not so much interested in pretty soap if it is kind of useless as actual soap. Or is dangerous. Or can go rancid. Or get chalky. Or give you chemical burns. For that reason, all I make are hot process soaps. They are not the prettiest soaps in the world, but they are effective and really great at being soap!
It is good on your skin and hair (better than luxury high price shampoos actually!) leaves you clean ad pleasantly scented without drying you out.
I hope you enjoyed this look into this poorly understood staple of every home. If you have any questions, I would be more than happy to answer them!