I don’t know when foaming hand soap became popular, but I have been buying it for a while. I love the instant lather versus regular liquid soap, but never liked how expensive it was. Not that it is a huge expense, but what can I say, I am cheap! Luckily I did some searching around and found out how cheap and easy it is to make. Now that I know, I am kind of pissed that I have spent so much money for what is 95% water all these years.

I made a few small experimental batches based on my reading and I think I have the ratios and process right. Grab your dispenser of choice. Pictured above is an old store bought foaming pump that we bought and have refilled for years, and a new one from amazon.
Directions:
Fill 2 Tablespoons of castile soap (olive oil based soap concentrate) for every 8 ounces of soap required. Add any desired essential oils. I used lime oil, because limes rock! 15 drops per 8 ounces of soap is a good place to start. Swish those two around in the container to mix, then gently fill the rest with water. Done! (Note, I modified the recipe slightly, see the update below)

You can make large volumes of the stuff for quick fills later. Use the 2 Tablespoons of soap, and 15 drops of oil to 8 ounces of fluid rule to make as much as you want.
My first batch was a festive peppermint hand soap. I started with water, then added the other ingredients. They didn’t mix as easily as doing the soap and oil first, so I would recommend main ingredients first, then water. Also on my first batch I added a teaspoon of olive oil. Some sources recommended it, some didn’t. It didn’t mix well, and a left vs right hand wash comparison with my non-olive oiled batch doesn’t seem to show any differences. Maybe because it didn’t mix well? If you want to try adding the olive oil, do it first, and get it combined well with the soap before adding water.
The bottle looks great in my bathroom! All these hand made soaps are translucent for some reason. The store bought ones are clear… Probably the soap acting as a surfactant has emulsified the essential oil. AKA, lots of tiny drops of oil in suspension make it look “cloudy”. Commercial ones must use alcohol based perfumes or something. Any who, both work great as a hand wash, leave a light smell, and provide a good lather. The picture above shows peppermint on the left, and lime on the right. The size and foam differences have more to do with the pump than the soap I think.
UPDATE!
I played around with a few more batches and have come to a different conclusion about the oil. It seems to help keep the soap and water mixed together better. Otherwise the soap wants to separate to the bottom. Also, the cloudiness fades with time. The final recipe is as follows:
Mix the following ingredients per 8 ounces of water.
- 2 Tablespoons of castile soap
- 1 Teaspoon of olive oil
- 15ish drops of essential oil
Mix those all together really well in the container and add the 8 ounces of water slowly. TADA! You made foaming hand soap.