How to Rebatch Soap

Rebatching soap is the last resort to save soap and is a great way to reuse some of those old soap scraps.

by Gina Napoli
PHOTO: Breanna/Flickr

Rebatching soap is the art of rescuing a failed soap batch or of making new soap out of old soap. Though it’s not recommended after the soap has hardened, you could rebatch soap if you forgot to include your additives, didn’t get your ingredients correct, got a false trace, or if you desire to mix soap batches for a certain appearance or fragrance. Every soapmaker rebatches differently and there are different methods according to the reason why you’re rebatching soap.

If you want to rebatch soap that hasn’t had a chance to harden, try heating it again. If you didn’t heat your soap to a high-enough temperature, you could have seen a “false trace” in your soap. This means that when you tested the soap by dropping a scoop into the rest of the batch, the soap looked as if it had traced, but what actually happened was that the fat reached room temperature and began to solidify. So reheating and getting your soap to truly trace should take care of the problem.

If your soap is not hard enough, this means there was too much fat in the recipe. You could try packaging it as a lotion or a lip balm. If you want to rebatch your soap, melt it down and try to balance the lye-to-fat ratio.

If you get in the shower to test your first batch of soap and find that it doesn’t lather, you don’t necessarily have to rebatch your soap. A good soap doesn’t necessarily have to lather to clean well. Sometimes a soap that lathers too much can dry out your skin.

Keep in mind that there are thousands of tricks to rebatching soap. Some soapmakers even make their own brands of soap using a rebatching process. Ever hear of French-milled soap? It is made from a specific rebatching process, that includes multiple rebatching steps. This process makes the soap milder and longer-lasting. The following instructions represent just one way rebatching soap can be done.

1. Grate soap pieces. It should look something like crayon shavings with chunks in it. A small cheese grater works well.

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2. Stir soap shavings with a little water in a stainless steel pot until you have a thin paste.

3. Place pot on low-medium heat and stir.

4. Watch for the soap mixture to liquefy. If it’s too stiff, add more water and keep heating. If you add too much water, boil it off, but don’t heat it
above 230 degrees F because it will be too hot to mix in the additives.

5. Remove soap mixture from heat.

6. Stir in your additives. (If it starts to harden before your additives are stirred in, place the pot back on the heat.)

7. Pour soap mixture into molds.

8. Cover your soap with plastic wrap and let it sit for 48 hours.

9. Pop soap out of molds. If your soap won’t immediately separate from the molds, place them somewhere cold for about two hours.

10. Place the soap bars in a cardboard box lined with waxed paper. Place in a warm, dry area that won’t be disturbed. Let the soap cure for at least six weeks.

11.  Use litmus paper to test the lye content of your finished soap. Be sure to wash off any soda ash that has formed before testing, as soda ash has a high pH value.

If your rebatched soap warps as it dries, try placing soap in a container with a lid to allow for minimal air flow.

Excerpt from the Popular Farming Series magabook Goats with permission from its publisher, BowTie magazines, a division of BowTie Inc. Purchase Goats here.

Also recommended:

Goat-farmer’s Cheese Recipe
How to Make Goat-milk Soap
Goat-milk Chive Butter Recipe
Goat-milk Mozzarella Recipe


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