How to rebatch soap in a slow cooker

May 28 2014 0 Comments Tags: self sufficiency, soap

I had made three batches of soap already, so feeling like a seasoned professional, I went ahead with another batch, even though my digital scales needed a new battery and I couldn't find my good thermometer.  I figured that I was so good at soap making now that I could be able to use my spare analogue scales and my cheese-making thermometer, even though the scale on both is pretty dodgy and the scales don't seem to zero properly.  Yes, the scene is set for a soap making disaster.  

Unlike cooking, in which the amounts don't have to be completely accurate, soapmaking is really a chemical reaction in which you do need to measure out very accurately or it won't work.  And I really should have known better!  I knew something was wrong when the soap took a very long time to reach trace.  The suspicion was confirmed when the soap did not set hard after several weeks in the mould.  Luckily all is not lost, it is possible to rebatch soap disasters, it just takes a slightly different method and some patience.

 

the unset disaster soap scooped out of the moulds

 

To rebatch soap successfully, it does help to know where you went wrong.  I know I used too much fat, but if I knew exactly how much extra fat it would be much easier to fix, as I could calculated how much more caustic to use to complete the reaction.  Unfortunately, my only option was to make another batch of soap with no superfat (exactly the right amount of caustic, or maybe a slight bit extra), process it using a hot process method (where you cook the soap in a pot until its completely reacted, with the failed soap batch added to the pot, and hope that the extra fat in the failed batch was enough to superfat the new batch and   balance everything out again.

This post is about how to fix a soap batch with too much fat.  If you have used too much caustic you can just melt the soap and add the amount of fat you need to fix it, but if its way too much caustic you might be better to use it for laundry soap.

This is the first time I've tried a hot process method and it was interesting to see how it worked.

First I made a batch of soap using the cold process method (and with 2% extra caustic).  I started it in a big pot so that I could fit all of the ruined soap in as well, and set up the pot in a double-boiler (my biggest cheese making pot, this is one way to get your cheese pots REALLY clean!).

Then Pete helped by stirring the ruined soap batches into the new batch while heating it over the double boiler.  When it was all combined we put the lid on and left it for 45 minutes.

The texture and colour changed as the soap cooked.  It was thick but fluffy and a little transparent. 

I tested the soap by taking some out of the pot and rolling it into balls, when it formed stable balls it was ready to pour into the moulds.

We poured it into the moulds and smoothed it out.  After 12 hours it was nearly hard.  

After a couple of days we cut the soap.  It wasn't as hard as a normal batch, but a huge improvement on the disaster batch.  I don't know if its soft because its still got too much fat, or if its was cooked too long (this can make it crumbly).
I tested the pH of the rebatched soap (top) and another soap from a previous batch (bottom) and I think the rebatch soap had a slightly higher pH, although its pretty hard to tell from that photo, the top pH strip is closer to 10, whereas the bottom one was definitely 9.  Its not a very precise system!  The other test that is recommended is to wash your hands with the soap and see if they rinse clean, or stay slippery.  I tested the soap and it felt normal, so I think its going to be ok.  Note that you can test the hot processed soap immediately because it has fully reacted, there shouldn't be any caustic left (unless you have got your ratios wrong!), you need to wait several weeks to do this test on cold processed soap.

Have you rebatched a soap disaster?  I am going to follow instructions more carefully from now on!

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