Technically, all handmade soap is “Glycerin Soap.” In many commercial soaps, all the extra glycerin (formed naturally by the cold process soap making method) is harvested out. Thus, all handmade soap is glycerin rich (since handmade soap makers don’t harvest out glycerin in their soap).
In today’s market, the term “Glycerin Soap” is commonly used to refer to clear soap. Generally, the clear soap has extra glycerin added to it to produce a very nourishing, moisturizing bar. Glycerin is a “humectant.” It draws moisture to itself; the theory is that if you wash with glycerin soap, a thin layer of glycerin will remain, drawing moisture to your skin.
Clear soap base can be purchased in large blocks to be melted down, colored and fragranced, and placed into molds (or used to make loaves of soap to be sliced). This type of soap is called “Melt and Pour” and the artistry of melt and pour is called “Soap Casting.” Melt and Pour soap making is gaining in popularity because of its ease of use. There are no significant safety measures (other than basic common sense – don’t put your hand in the hot soap, don’t cut your finger off with the knife etc…) needed for soap casting. Children can do it. It’s a great outlet for creative types.