February 8, 2013

Making Liquid Rosin Soap

Last year I started making soap. The initial impetus was to make shave soap to support my transition to homebrew straight shaving, followed by the desire to supply our modest needs for bar soap. I also wanted to supplant the Dr. Bronner's liquid soap I like to use for bathing, and this was my first effort in that area.

The library didn't have an orderable copy of Making Natural Liquid Soaps, by Catherine Failor, so I ordered one from Amazon. We considered using natural rosin for a project at work and didn't end up using it, so I had a ready supply of rosin which would otherwise cost money for my company to dispose of. I came to enjoy the scent of rosin, and liked the idea of reusing waste material, so I thought I would try making some rosin soap. I had also read that it makes a nice, dense lather. For this soap I used Honduran Rosin; not sure where it was originally purchased.

I made up a version of my soap spreadsheet for this soap, which is based on a recipe from Failor, and proceeded with the version of the process which entails hot processing the soap, then diluting with water.

I mixed up my KOH solution.

Heated up the oils. The pot in the back corner has the rosin, which I only add after the other oils trace since otherwise it causes the mixture to seize up prematurely.

Oils and hydroxide have traced.

After adding the rosin and cooking for a while.

Diluting with water after cooking for 3 hrs.

After simmering for a few hours, some soap was still not dissolved, so I added about an extra 50ml of water.

Child 1 helped me put the finished soap in jars, after adding borax solution and fragrance and cooling for a bit in the pot.

One thing I like about Dr B's (besides the wacky text covering the outside of the bottle, which is amusing) is that the peppermint variety leaves the tender parts of your skin feeling tingly and pleasantly scoured. I think this is down to the fragrance additive, since it doesn't really happen with the lavender variety. Failor's book recommends adding scent at 1%; I tried adding peppermint oil at 2%. Its quite noticeable, but not up to the skin tingling level of Dr. B's. Maybe next time I'll try 4%. Perhaps the difference is that I'm using Mentha Piperita while Dr. B's ingredients list Mentha Arvensis.

I put some of this soap in a poly squirt bottle and have been bathing with it for a couple weeks now. For better or worse, I don't have any hair to speak of on my head, so this bottle of liquid soap is the only product I need for bathing. In reality, I could just use the bar soap we have around and rationalize the personal care products a bit, but for now I'm used to using liquid soap. Its pretty nice, if not quite as exciting as Dr. B's. Its also lower viscosity than Dr. B's. Maybe next time I'll try for a lower dilution rate, or add a viscosity modifier.


The Lady Marah said...

I know this post is old, but I'd love if you could share a little more detail on your use of Rosin. I also have Failor's book, but she deosn't describe how to use it. Did you calculate your lye amounts to include the Rosin as well, or did you treat it like a superfat oil?

Holly said...

Hi there! This was a while ago so I'm trying to remember what I did. The rosin is treated as a real oil, not just a superfat oil. It presents two challenges. One is what to use for the sap value, the other is that it siezes up the mixture if added with the other oils.

I think when I made bar soap with the rosin I found a sap value on a website somewhere for rosin.

For this liquid soap, I started with Failor's recipe in my spreadsheet, with known sap values for coconut and olive oils, then adjusted the sap value for the rosin until the output quantity from the spreadsheet was equal to the amount called for in the Failor recipe. Looking at the spreadsheet:


I seem to have ended up at a value of 182 for the rosin.