What’s the difference between Cold-Process and Hot-Process soap?
Hot Process soap uses heat from an external source to accelerate saponification, the process by which fats and an alkali combine to create soap. While Cold-Process often uses heat early on to warm the base oils, once the oils and sodium hydroxide are mixed, heat from the process itself is relied on to finish saponification.
What’s the difference between Cold/Hot-Process Soap and Glycerin soap?
There are two answers. Technically, all true soap (as defined by the FDA) is glycerin soap, since glycerin is a natural by-product of saponification.
What most people know as glycerin soap – transparent or opaque bars, often with fun things floating in them – is different. That glycerin soap usually takes saponification a couple of steps further. A sugar-alcohol solution is added to the saponified mixture along with extra glycerin. The alcohol solution helps maintain transparency, and the extra glycerin balances the drying nature of the alcohol.
How does Melt-and-Pour soap differ?
Melt-and-pour soap is made a from a pre-made base usually sold in blocks. Soapmakers melt a portion of the base, adding colorants, scent agents, exfoliants, and moisturizers to the melted portion. This is also the point at which swirls and decorative objects are added. While it’s still hot, the finished base is poured into molds.
Most true soap doesn’t melt down well, and as a result doesn’t work well as a good melt-and-pour base. Glycerin soap and soap made with white coconut oil fare better than most, which is why melt-and-pour bases are usually made from one of these two.
The melt-and-pour process provides an easy way to create homemade soaps in a variety of shapes and styles. While not officially soapmaking, melt-and-pour is a great way to be creative with soap and to do it safely enough that it’s fine for use in crafts with children.