Is it just me, or is my soap shrinking?
The answer is clear: yes, the bar of soap you bought from me a few months ago is now just a little bit smaller. The band may be fitting a bit looser (wish my belt would, but *shrug*). So what the heck is going on?
Soap at it’s most basic is a mixture of oil, lye, and water. It takes approximately 5 days for all of the lye in the bar to go through the process of saponification, that is, the process of turning oil into soap. If you tried to use the bar before that 5 days was up, the soap would be harsh and possibly even burn or irritate your skin. After saponification is over, soap still has to go through the additional process of curing. This is where soap makers allow the soap to set out in a cool, dry area to allow any excess water to evaporate off. A typical cure time is often between 4 to 6 weeks, but I have bars that I cure for up to 3 months (looking at you Pumpkin Coconut Bastille) before I will sell them.
The process of curing does not stop once that initial cure time is over. It just means that most of the water has evaporated and the bar isn’t going to melt away the first time it touches water. Luckily, this process is a good thing! If your bar has shrunk a bit, what’s left behind is a slightly firmer, more sturdy bar than it was when you first bought it.