The [Soap] Art of Chemistry
Cold & Hot Process soap crafting is a real art of chemistry. In it's basic cleansing form, soap is made from the formulation of lye, water, oils and fats. The solid cleansing bar that is formed is from the resulting chemical reaction of these ingredients, called saponification.
CHEW THE FAT
Lye, or sodium hydroxide, is a caustic chemical that when dissolved in water, has a strong alkalinity, a pH of 14. This high caustic solution is what dissolves fats/oils, creating salts, free fatty acids (excess oils) and glycerin (a humectant; a 'moisturizer' that binds to the skin to retain moisture), which forms into soap. When soap is formulated properly, a bar will be a very mild and neutral pH of 7-8, with no active lye left in the bar, and lots of natural skin softening, moisturizing goodness.
Soap was originally made by using the lye/water solution to render animal fats, since they were cheap and readily available. You can still see this ingredient in businesses that use animal byproducts, listed as sodium tallowate (usually beef origin). While animal fats are probably still cheap, and readily available. Most businesses (like ours) choose to use plant based ingredients.
ALL NATURALLY MADE SOAPS CONTAIN LYE.
Whether it is a solid bar that uses sodium hydroxide, or a liquid wash that contains potassium hydroxide, all soaps are made with this key ingredients. In bar soap form, you may have seen this ingredient listed as
-food grade lye
-saponified oils/fats (coconut, olive, etc)
-sodium _____ate (which is the actual term of the chemical reaction of sodium hydroxide + whatever fat/oil used. Ex, sodium cocoate, sodium palmate, etc).
If you see none of these terms, chances are it is synthetic detergent bar made with sulfates other other synthetics. Sulfate' is the salt from sulfuric acid, a much more harsh and drying ingredient used in most of today's big brand cosmetics and cleansing products. Sometimes, for troublesome acne, sulfuric acid is used as a drying agent to dry out pimples. But this is a very strong acid that will dry out skin and in large amounts even in it's salt reduction it's not an ingredient that should be used all over the scalp and hair (as in shampoos), or all over the body (as in body washes).
NOT SO SOLID AS A ROCK.
Plant based soaps are made with soft oils such as olive and avocado (a castille bar is a soap bar in which is fat part of the formula is 100% olive oil), and hard fats such as coconut, palm, shea and cocoa which help create a hard bar. But even the hardest natural bars have to be taken care of. Even after a minimum curing time of 4 weeks (which allows most of the water to evaporate from the bar), soap bars contain a lot of natural glycerin, which is a humectant that will draw water from the puddle you left it your bar in in, turning your bar into a pile of mush. After use, always dry the bar out on an open slotted soap dish or rack, so that the bar can stay well ventilated and last much longer.
Please read 'Fear-mongering in the Soaping Industry' for our list of ingredients, and to read up on how great natural soap really is.