After finally getting around to publishing a basic overview on liquid soap, I thought I’d kick off my new litany of liquid soap inspired recipes with a simple peppermint hand soap. This is the type of soap you can pop in a pump-top bottle and use to wash your hands, or use in the shower as a body wash or shampoo. It’s pretty darn all-purpose, and I think that’s awesome.
You’ll want to start with some liquid soap paste. I’m using my basic soap paste because I still have a lot of it on hand (it’s also awesome). We’ll kick this off by diluting it into something less paste-like, and more soap-like. You’ll always want to use less water than soap paste in order to get a final product that’s thicker than skim milk (and one that won’t mould—too much water makes for a pH that is too low to inhibit bacterial growth for long).
I find it useful to think of diluting the soap paste as more of a softening. You basically add a bit of hot water to the paste in an air tight container, use a fork to lightly mush the paste around, and then seal it and let it sit. If you happen to be around four or so hours later, give it a quick squishing/mashing and a wee blast in the microwave (20–30 seconds), re-seal it, and let it sit some more. I’ve found that after about 9 hours the soap paste will have absorbed all the water, and you’ll have something more liquid soap-like than paste-like.
I find this method preferable to trying to cook it at all as it gives you a lot more control over your inputs. As soon as you introduce simmering and cooking, you introduce pretty large amounts of evaporation, and when you’re done you really have no idea how much water is in your soap. Plus, the number of times I’ve totally forgotten about my soap/had it boil over and make a stinky, soapy mess is flat out embarrassing.
Once you’ve got a container of liquid soap, the rest is easy. Add some peppermint essential oil until you like the way it smells. Stir, decant into a pump top or squeeze bottle, and voila! Soap 🙂
2019 update: I’m afraid I can’t offer much in the way of detailed troubleshooting information for this project as I haven’t made liquid soap using KOH in well over 3 years and my memory of the process is limited to my notes, which you’re reading here. Sorry!
Liquid Peppermint Hand Soap
100g liquid soap paste
60g just-boiled water
25–50 drops peppermint essential oil (to preference, basically)
Weigh your soap paste out into a sturdy, airtight container with a lid. Choose something that’s neither super tall and narrow, or very broad based, giving you room to mash the soap about while leaving it submerged.
Mash the paste down a bit with a fork, and add the just-boiled water (the paste should be totally submerged, so if it isn’t, mush it down more). Seal the container and let it sit for 3–4 hours.
At this point I like to twist the fork in the paste a bit to expose some new parts of the paste, give the container a quick 20–30 second blast in the microwave, re-seal it, and leave it for another few hours. At this point you should notice that the water is noticeably more viscous than it was.
After about 9 hours you should have a container of thinner soap paste (liquid soap!) rather than soap paste sitting in water.
Decant the soap into a pump-top bottle or a squeeze bottle, and use for all your soapy needs!