Can you rebatch soap by melting it with new oils?

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Oliveandash

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Hi,
I made a 3lb batch of soap, which I was hoping to be able to reuse. I read that you can melt a percentage of an old batch with fresh oils to make a new batch. Has anyone tried this method? Thoughts or things I should know before I try it? Obviously you would deduct a percentage of the oils and possibly scent of it was strong enough from the new batch, would you also deduct a percentage from the lye and water?
Thanks so much!
 

DeeAnna

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I think you're over complicating the situation.

Think of the old soap just the same as any other additive like oatmeal or salt. You don't include the old soap when doing the calculations for the new soap. (I'm assuming the old soap is properly made -- in other words, it's not lye heavy).

Just design a recipe for the new soap as you would normally do as if you weren't adding old soap to it. This also goes for the fragrance amount, unless you think the old soap has a strong enough scent that it can be used to also scent the new soap.

The old soap is then stirred into to the new soap when the new batter is at a stable emulsion or light trace.

I don't know that I'd melt the old soap, however. I would grate or shred it and stir the shreds into the new batter to make a "confetti soap". Search SMF for confetti soap for ideas. I have had the best luck mixing 1 part shreds to 2 parts new soap batter by weight. If I add more shreds than that, I've had trouble getting the shreds mixed into the batter well enough.

But if you do want to melt the old soap, yes, that can be done too. I think some people have melted the soap with the oils for the new batch, although I'm speaking from vague memory here -- there might be more to this method than I recall.
 
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earlene

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Hi,
I made a 3lb batch of soap, which I was hoping to be able to reuse. I read that you can melt a percentage of an old batch with fresh oils to make a new batch. Has anyone tried this method? Thoughts or things I should know before I try it? Obviously you would deduct a percentage of the oils and possibly scent of it was strong enough from the new batch, would you also deduct a percentage from the lye and water?
Thanks so much!
I have done this. I called it old and new soap. Some people call it confetti soap. But I did not deduct anything from the new batch of oils. The old soap is already saponified, so there is no need to account for the oils and ingredients, unless your old soap is lye heavy or has too much superfat.

IF it is lye heavy, make the new soap with a higher superfat to accommodate. If it has an excessively high superfat, make the new soap with a low superfat to compensate.

Before you mix them together (be it in a crock pot or a bowl or even the soap mold) make sure you get the grated or chopped (or however you prepare the old soap for adding to the new soap) NICE AND WET ahead of time. Deduct the amount of water you use to moisten the old soap from your lye solution for your new soap.

Otherwise, treat the new soap like it is a stand-alone soap with calculations for only that particular batch.

The reason for getting the grated old soap wet is to encourage adhesion and to discourage air pockets. Although the soapmaker in the above video did not appear to have air pockets around her soap shavings (which she did not pre-moisten), I have had many air pockets around grated soap when using that method, so I now pre-moisten. It may have something to do with how liquid the new recipe is, or the amount and/or size of shavings as well.

You can create landscapes in soap with the grated bits or whatever type of design you want. Or you can just mix them together to get a speckled look to your soap.
 

ResolvableOwl

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It also depends on your expectations of the structure of the final soap. Confetti soap embraces the idea of visible soap shreds. The blended-confetti soap that @Mobjack Bay has linked, has a finer pattern, but still a rough, sand-like appearance – at least for the eye. I second @earlene's pointer to timely moistening the shreds, to help them acclimate, so that they don't cause so much of a “sandpaper” effect.

If you want a “smooth” bar, however, you won't get around a hot technique. The boundary between rebatching and HP is vague.
First note that soap won't dissolve in oil (or at least only to a negligible percentage) – if this were the case, HP saponification would be a whole lot easier!
Soap also won't “melt” (turn into a liquid state comparable to CP batter), but at most turn into a state comparable to the “vaseline” or “applesauce” states of HP batter.
If you want to achieve a smooth batter that is partly based on old soap, either make a hot rebatch batter and add lye + oils to it, or dissolve the old soap in the lye (but beware of curdling – sodium hydroxide is a strong salting-out agent).


All in all, as appealing a “modular design” soap assembly kit might sound, it's probably not worth the extra effort, and the results more often than not can't compete with soap that is either made from scratch (CP, HP), or embraces its composition (confetti).
 

Oliveandash

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It also depends on your expectations of the structure of the final soap. Confetti soap embraces the idea of visible soap shreds. The blended-confetti soap that @Mobjack Bay has linked, has a finer pattern, but still a rough, sand-like appearance – at least for the eye. I second @earlene's pointer to timely moistening the shreds, to help them acclimate, so that they don't cause so much of a “sandpaper” effect.

If you want a “smooth” bar, however, you won't get around a hot technique. The boundary between rebatching and HP is vague.
First note that soap won't dissolve in oil (or at least only to a negligible percentage) – if this were the case, HP saponification would be a whole lot easier!
Soap also won't “melt” (turn into a liquid state comparable to CP batter), but at most turn into a state comparable to the “vaseline” or “applesauce” states of HP batter.
If you want to achieve a smooth batter that is partly based on old soap, either make a hot rebatch batter and add lye + oils to it, or dissolve the old soap in the lye (but beware of curdling – sodium hydroxide is a strong salting-out agent).


All in all, as appealing a “modular design” soap assembly kit might sound, it's probably not worth the extra effort, and the results more often than not can't compete with soap that is either made from scratch (CP, HP), or embraces its composition (confetti).
Hmmm interesting… thanks for the great tips everyone!!😊
 

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