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How do you save a soap with too little lye?

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Skybluesky

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Hi,
I don´t usually have time for forums but I sometimes check the posts here whenever I can read them and I have a doubt that´s been bothering me and would like to hear from your experience.

Is it possible to successfully add more lye to a low lye soap on rebatching? I mean, how do you add a soda solution to already partially saponified soap, till it´s homogeneous soap?
And if so, how do you do it?
Some Internet sites, assure that it is possible. All my tries ended in crumbly soap that I had to throw out, despite my attempts to melt the soap well.
 

Primrose

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I have accidentally made a couple batches with a high superfat. It remained soft for longer but I gave it a longer cure and it ended up fine. I kept in mind it would probably be more likely to develop DOS and kept it for my own use
 

atiz

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You could salt it out perhaps? Or does that only work for lye-heavy soap?
There are some posts on the forum about how to do that but I've never tried (seems kind of a lot of work...).
 

DeeAnna

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Yes, it can be done. Whether it's worth the effort is another thing. You haven't explained the situation so I don't have a clue what would be the best advice to give.

If the amount of soap is small, you might be better off just discarding it rather than spending a lot of time fixing the problem. Newbies want to save every scrap, and I understand that, but sometimes the better solution is to accept failure and move on.

If the fat excess is moderate to small, grate the soap and add the soap shreds to new soap batter with a low superfat. Search for "confetti soap", which is what this method is.

If you do know how much NaOH is needed to fix the soap and the amount is fairly small, do a rebatch method using a generous amount of water and add the NaOH during the rebatch. You need to use sufficient water to get the soap really fluid so the lye can do its job -- more than you'd normally want to use.

If the fat excess is quite large and you don't know how much extra NaOH is required, then use a "boiled" soap making method to saponify the excess fat. Melt the soap in a weak lye solution containing your best guess of the extra NaOH needed, simmer for awhile, test for zap, if no zap, add a bit more NaOH, simmer, test, etc. until the soap mixture has a very slight zap. Salt-out the soap to remove excess water and excess lye. I explain the salting-out method in more detail on my website -- see https://classicbells.com/soap/saltOutTut.asp
 

Skybluesky

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@atiz I never tried salting out on rebatch. I thought about it but never risked it. I several times pondered rebatching using and adaptation of the industrial method where you salt the soap but I haven´t got enough knowledge or experience of it or even the right tools/ recipients - I´ll have to try it one of these days.

I had read that Soap Queen post before but other sources claim it can be done, so hence my doubts.

@DeeAnna, thanks for the link, it has interesting information and clarifies some things for me. :)
So, if trying again with a "boiled" soap method, by "weak lye solution" do you mean a solution with just a few grams of NAOH or a solution where NAOH is very diluted? And in this case, does the strength of the solution matter more than the amount of Lye?
Sorry, I have many old doubts and haven't been able to confirm or dismiss them.

Last time I rebatched a soap short on lye I tried chopping as small as I could and maybe it wasn´t small enough, so that could have contributed to being hard to melt. Still, my overall experience is that soap like this is hard to melt well, even on an oven, and after partial saponification, my difficulty is getting it to mix with new lye. The result ended up being a sort of salting-out, where the soap gets crumblier or harder - I though these were not good and were ruined...

I had several cases of soap short on lye: scale with a weak battery, lye that had been opened for toooo long, and lye that was bought at a Chinese store and turned out to be less pure than usual.
According to the Internet, NAOH made in countries like India, Iran and even China, don't always have a high grade of purity.
All these failed batches obviously bothered me. Some were about 2 pounds, which for me is a big batch of soap and a waste of oil/fat.


These are links of a man in Brazil that makes soap after a lifetime working in chemistry (according to his site). He has some interesting experiments with "industrial" type methods of making soap and even made his own improved pan to easily extract the liquid:
https://www.youtube.com/channel/UC_WhAgvir7mbXZ_Rmsl9aMw
 

DeeAnna

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"...So, if trying again with a "boiled" soap method, by "weak lye solution" do you mean a solution with just a few grams of NAOH or a solution where NAOH is very diluted? And in this case, does the strength of the solution matter more than the amount of Lye?..."

Concentration (strength of solution) is not a critical issue.

You need to use enough NaOH to sufficiently saponify the excess fat. If you do not provide enough NaOH molecules, you won't get the results you want regardless of how much or little water you use.

I give a method of estimating the NaOH required in the link (see my post above). Follow it.
 

Skybluesky

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This exchange of ideas really helped me understand rebatching and boiled soap better, so thanks to all for helping! As soon as I have a chance I´ll try the boiled method.
 

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