Wednesday, May 28, 2014

How to rebatch a soap disaster

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, soap making is really a chemical reaction in which you do need to measure out very accurately or it won't work.  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!

My other soap posts:

Natural soap using beef tallow


5 comments:

  1. Hi Liz, It's easy to follow a recipe and get it right. It's even easier to get it wrong. But recovery from the getting it wrong is the true sign of a master. Well done.

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  2. Oh, you're braver than me. I wouldn't know how to calculate what was over added in order to try and rectify.

    Well done :)

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  3. Yes, and like you , it was when I got really confident with it . I had been trying to prevent gel phase in the goat milk soaps as they were getting way , way too hot at saponifcation...but what I accidently did by mixing it in a double bowl of ice was prevent trace happening and was getting a false trace. Then the soaps never went hard. I had to grate it and melt it and then decided to make a poppy seed scrub bar with lots of natural colours so that the soap didn't look funny after rebatching. Turned out to be one of my best inventions!
    But now I know not to stop gel phase from happening because that is actually the key to a good hard soap , as long as it doesn't get too hot.

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  4. Hello Liz, just found your blog and happy I did. We live in Illinois on an organic farm and I make tons of soap. Yes, I have to rebatch at times usually because I just like to. You can also use a crockpot to rebatch just throw your soap in there and put it on low, Stir as needed and remold. Do you use a lye calculator for best accuracy ? I love the one here https://www.thesage.com/calcs/LyeCalc.html. Have fun!

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  5. My colossal disaster was also a milk soap that had a false trace. I rebatched it and it came out ok, but it is definitely "different" from cold process. I hope I don't have to do it again! Thank you for sharing this at the HomeAcre Hop; I hope you'll join us again this Thursday.
    Kathi at Oak Hill Homestead

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Thanks, I appreciate all your comments, suggestions and questions, but I don't always get time to reply right away. If you need me to reply personally to a question, please leave your email address in the comment or in your profile, or email me directly on eight.acres.liz at gmail.com

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