What about the glycerine?

As you remember from the chemistry equation above, soap making naturally generates glycerine. Glycerine is called a humectant, meaning that it retains moisture, which makes it a natural skin moisturizer. Curiously, most of the bars of soap you see on the shelves at the grocery store don't mention glycerine as one of the ingredients. The reason is that it has been removed.

Nearly all mass-produced soap has had the glycerine removed from it. Why? Because it can be sold as a separate commodity with perhaps a greater fiscal return than would be derived by leaving it in the soap. Glycerine is used in pharmaceuticals, cosmetics, food products, cellophane, and it is used in explosives. Remember nitroglycerine?

An interesting note about glycerine's being used in the production of explosives comes from Britain during World War II. At that time, British soap makers were regulated by their government. This was not to ensure a clean populace, but rather to ensure that the maximum amount of glycerine would be available to product ordnance for the war effort. Soap is dynamite!

Also, as a matter of clarification, the term "glycerine soap" has become synonymous with "transparent soap", but glycerine cannot create transparency in a soap bar by itself. "Glycerine soap" is just another improperly used household word that arose from a misunderstanding. Soap is made transparent by the addition of certain alcohols and sugars. These are dissolved with pure soap and resolidified, causing the molecular structure to change, and letting the light through. Pure soap, even with lots of glycerine in it, is still opaque.

Another thing about transparent "soap" bars: some transparent bars are not even soap. Triethanolamine is an example of a surfactant that is also transparent, and it is used in some cleansing bars.