There are two primary methods of soap making: cold process and hot process.
Cold process soap is made by keeping the temperature of the oils and lye relatively low (room temp. to 110° or so) during the making process. “Cold process” is a bit of a misleading term, though, in that the soap does eventually reach high temperatures, and will usually reach temperatures so high that the innermost portion actually turns to gel. This is called the “gel phase”. Some soapers avoid this since it does change the final appearance. We like to let our soap do its thing, and embrace the gel.
Hot process is very similar, however, heat is applied during the making process and is forced to gel throughout. This process gives the final soap a more “rustic” appearance and doesn’t allow for much creativity, as the soap is very thick once thoroughly mixed.
I prefer the cold process method, which keeps the soap fluid allowing it to be poured, and swirled and all that fun stuff--because I’m an artist, and I can’t help but make our soap pretty. It’s simply impossible. The only exception is for our shave soap, which is made with the hot process method. I, oddly, don’t feel the need to make that one pretty.
No matter the process used, soap is best when allowed to cure for a length of time. We prefer to cure ours for at least 4 weeks. This allows the soap to become harder, which makes it last longer, and it will enable the process of saponification to complete—resulting in a mild bar of soap.