Most of the soaping book and online information recommend using between 5-10% castor oil in soap recipes to boost bubble. It's said that castor oil contributes to lather power of soap. However, more recent studies show that when making 100% castor oil soap the soap has very little to none lather. Shocked?! I was when I first read it! So what is the truth about castor oil in soap? What exactly does it do in a bar of soap? Here are some facts we know about castor oil in soap:
- According to wikipedia 85-95% of the fatty acid in castor oil is Ricinoleic with the remaining spread across Oleic and Linoleic. This fatty acid profile is unique and none like others!
- Recipes using high percentage castor oil tend to trace faster.
- Soap made with high percentage castor oil tends to be softer.
- Soap made with high percentage castor oil tends to melt faster.
Now the million dollar question is, if castor oil really boost bubble in soap, why doesn't the 100% castor soap lather at all? On the other hand, if castor oil does not boost bubble in soap, why would all information suggest that? And if castor oil is not used to boost lather in soap what do we use it in our recipes for? To answer all these mysteries I decided to do a little scientific experiment of my own.
I simply just created a simple 3-oil recipe that takes up 75% of the oil weight with the remaining 25% being the variables to play with combination with and without castor oil.
- Soap #1: coconut oil 20% palm oil 20% olive oil 35% castor oil 25%
- Soap #2: coconut oil 20% palm oil 20% olive oil 35% avocado oil 15% cocoa butter 10%
- Soap 3: coconut oil 20% palm oil 20% olive oil 35% hazelnut oil 15% cocoa butter 10%
This first group is used to prove if castor oil soap melts faster than other soap without castor oil. They would be made with the same water content with the same size and material mold. As of now these soap had been made. I will cure the soap for 2 weeks, cut a piece from each block and weight them to be exactly the same gram and pretty much the same dimensions. Then I will dip each piece into a glass of water (same type of glass with same amount of water) for a period of 48 hours. Each piece of soap will be taken out and weighted at 2 hour, 6 hour, 12 hour, 24 hour and the last 48 hour mark. This is to examine the water solubility.
- Soap #4: coconut oil 20% palm oil 20% olive oil 35% avocado oil 15% cocoa butter 10% water contains 5% oil weight brown sugar (sorry, I don't have refined white sugar in my household)
- Soap #5: coconut oil 20% palm oil 20% olive oil 35% avocado oil 15% cocoa butter 5% castor oil 5%
This second group of soap is to be used together with Soap #2 to examine if castor oil in deed contributes to bubble boosting power like all the information points to. As of now Soap #4 & 5 had also been made already. They will be cure for the same 2 weeks before doing the tumbling test with water. I will again cut a similar dimension and weight piece from each block, pre-washed my hands, then go for 10 second and 20 second tumble lathering test in my kitchen sink.
The final part of this experiment is a bit harder. How do I find out if castor oil really contributes to "moisturizing" property of soap? What feels moisturizing to one may not be the same to others. Here's where I ask my readers if any of you would like to participate in my little scientific experiment. Each volunteer will receive 5 different samples of soap marked with alphabet letters that are no associated with the soap numbers I assigned. This is to ensure there are no bias in the final result. Each participant will have to follow my instructions and perform the same tumbling in the sink test then fill out my survey. Don't forget to leave your name and contact email in a short comment and I will get in touch with you shortly!