I thought I'd write a little post about soap. I'm still learning how to make it properly. Lately I've had a couple of bad batches, and a few good ones.
It's crucial for soap to come to the gel stage after putting it into the mold, the stage where it gets hot, looks like a gel (especially in the center, where it's hottest), and darkens a bit. The gel stage occurs when the newly poured soap is allowed to get very hot in the mold. The saponification process in the mold makes this heat, but the heat must be kept in the soap, and not allowed to escape quickly. Thus it's important to wrap the molds well, to keep the warmth in and let the soap cool very slowly.
Naturally, small molds or thin molds lose their heat most quickly. I have various molds: 1) large, thick wooden molds, 2) orange juice cans, 3) silicone baking molds, 4) clear plastic soap molds from Michael's. It's no surprise that the thick wooden molds insulate the soap well, and retain the heat until the soap fully gels. That soap hardens well afterward. The orange juice cans also insulate rather well; the cardboard and wax lining do a good job. The silicone baking molds are fairly good, but the smaller the individual soap wells, the worse they do. I have one silicone mold that has 6 large hearts; it does okay. Another silicone mold has about 20 tiny soap molds in it, and these little molds just can't retain heat for long.
Soaps that aren't allowed to gel, heat up, and cool slowly, turn out soft and mushy, and never fully harden. The clear plastic mold was disastrous recently. It did not gel, did not solidify, and the soap remained soft and mushy. I could not remove the soap cleanly but could not repour it either. The mushy soaps in the silicone baking molds were somewhat rescued by placing the molds and soap in a low oven. The heat of the oven took the place of the gelling, to some degree. Those soaps hardened acceptably, although not all of them were pretty.
But the clear mold was the worst. I decided to put it into a warm oven too -- how stupid was that?! I forgot about it, and the plastic melted slightly, warping the soaps, which I then could not remove well at all. I dug them out. (Talk about ugly soap.) And the clear mold is no longer usable.
Now ... I wrap up all my soaps in warm towels after pouring them into molds. It's time consuming. I also place plastic wrap on top of the little soaps, to give them additional help in retaining their heat. Then I wrap them in towels. I hope this little post helps someone else trying to improve their soap-making skills.