February 7, 2013

Making Transparent Rosin Soap

Last year, I set out to make soap. My first try was a cold processed castile soap, which didn't turn out great. To satisfy our needs for hand soap at our house, I decided to try to make some transparent soap.

Luckily, the Minuteman Library Network had an orderable copy of Making Transparent Soap, by Katherine Failor. Go Minuteman!

Last summer I made about 2kg of transparent soap bars using a recipe based on the Jurassic Soap recipe from this book. I tried to process them in the crock pot using the method where you add the alcohol along with the hydroxide solution and cook. In Failor's books, she puts a tight fitting plastic head on her pot which contains the foam generated by this process. I figured with plenty of head room in the crock pot and a more controlled source of heat I wouldn't have to worry about foam over. I was wrong, and ended up needing to completely disassemble the crock pot to clean soap out of every crevice and off every surface. Oops!

The soap made nice, hard, neutral and well performing bars, but for some reason they clouded up around the edges of my soap form. I put the form in the freezer after I poured it, and the clouding was worst around the edges where the soap was touching the form. If anyone has any ideas on how to avoid this next time, please let me know.

The bars are pleasant to use and the rosin gave them a subtle but enjoyable odor. I've given away quite a few of these, but I think we'll still have enough to make it a whole year before needing another batch.

I get the feeling that some people find receiving home made soap as a gift a little... weird. Can you imagine??!

My spreadsheet from this soap run can be found here.

On the same day, I also made a new batch of shave soap, mostly along the lines of my previous effort. This time I did adjust the recipe a bit, replacing castor oil with rosin, hot processing the soap, and using avocado oil for a post-process superfat. These bars came out so ugly that I didn't bother to take pictures of them, but their performance is quite nice and I've been shaving with them for about 5 months now. You can find the recipe at the bottom of this spreadsheet.


David Powers said...

Would you kindly list your supplier for Rosin?

Holly Gates said...

The rosin for this and a few other batches of soap was Honduran Rosin which I took from a pile destined for the garbage at work. We had bought in all kinds of rosin and rosin derivatives to formulate a polymer coating for use in microtexturing of silicon wafers for solar cells. In one of the chemical stock cleanouts, all the unused rosins were being tossed and I wondered if maybe it could be used in soap. After some internet research it did seem that it could be partially saponified and brought some nice qualities to soap when used as a minority ingredient. That rosin was I think from


which is a distributor for


I'm just gearing up to do a new batch of this soap and found my rosin supply low, so I bought a bag of pine gum rosin from Amazon:


Well see how it does, but I'm expecting it will work fine.

Susan Messenger said...

Hi there.

If you don't want anything weird happening in your soap after pouring...just leave it somewhere cold.

Don't freeze the soap. Allow the soap molecules to line themselves up of their own accord.

The temperature of the soap bar should be as low as 20C before removing.

Rosin is also used as a baseball supply to help the player grip the bat. check out a baseball supplies place for a rosin bag.

Susi Messenger

Susan Messenger said...

I have just read your spreadsheet for the soap you had on the blog.
Your superfat was at 2%.
If you aim for a 0% superfat your transparency will be much better
Hope this helps
Susi Messenger
South Australia

Liz Tóth said...

to Dave Powers, in case you're still looking, I've been trying to source rosin for for soap for about a year now, and finally twigged onto the ballet thing: they use it for pointe work, to make shoes less slippery. The type they use does not contain fillers - the stuff for sports (e.g. the type you get in rosin bags for baseball) contains fillers (magnesium oxide? not sure if that's right but it didn't sound like something that you want in soap)... to keep it from clumping. The dance rosin doesn't have that. Bought some, tried it yesterday: it turned out clear on the first try.
Good luck with it!