How to use vinegar to harden your soap

When you use vinegar to replace some or all of your water, the acetic acid in the vinegar reacts with sodium hydroxide to form sodium acetate. Sodium acetate works like sodium lactate to harden your soap, except all you have to buy is vinegar.

I promised simpler instructions for folks who don't want to get so exacting with the math. I have done this technique with white vinegar, but the instructions will work with any vinegar that contains 5% acetic acid.

First decide how much sodium acetate you want in the soap. Try maybe 1 or 2% of the oil amount for your first time out. Lets say 2% for the example.

Multiply your oil amount by the percentage you chose:
2% of 500 g oil is 500 x .02 = 10 g sodium acetate (SA) desired

Multiply the SA amount by 14.6 for the amount of water to replace with vinegar:
10 * 14.6 = 146 g vinegar

Multiply the SA amount by .49 for the amount of extra NaOH to add to what your lye calculator told you:
10 x .49 = 4.9 g extra NaOH

That's all there is to it.

If you happen to want to replace ALL your water with vinegar, multiply your liquid amount by .0333 to get the amount of extra NaOH to add.

The more exacting explanation of the math, for those who want it, is here:

http://www.soapmakingforum.com/showthread.php?t=57991

Thankyou TOMH, it makes if much simpler

Damn and I just bought a 5L bottle of sodium lactate too I will keep this in mind when that bottle runs out in a year or three. hahaha

TOHM, as we know, I suck at math, but here are my observations. I was playing with the numbers to figure out if I wanted to add the extra lye to compensate for the vinegar and keep my super fat at my normal 8% or if I wanted to recalculate the recipe with a lower SF of 1 or 2% and not use the extra lye. In all of my calculations, the difference was negligible. I don't have my notes with me, (I suck at organization, too) but I have a piece of paper with a note that has "0% SF at 100%=(+/-)6.55 SF, 75%= (+/-) 7.5 SF, 50% = (+/-) 7 SF, 25%= (+/-) 4% SF." This is my shorthand for zero SF replacing water by X% yields a SF of Y (give or take a few .01s). So, I guess my point is, doing a low SF and not compensating the extra lye does yield a safe (not lye heavy and in some cases, well SFd) product. I probably wouldn't do this with a 100 pound batch because there's a much higher probability of error in that amount of volume. However, once I perfected my recipes and techniques on a small scale, adapting them to a large scale operation "shouldn't" be difficult. The key is making sure my scales are accurate, calibrated and I double (even triple) check my weights before lye meets oils. So says the woman commonly known as "Sux at Math."

So, all you sciency peeps: Tell me why my logic (as well as math) sux and why I should not do it this way. Go ahead. Don't hold back. I can take it. I've got my "big girl panties" on.

(Now, to figure out a way out of the EDTA math...)

great info, gotta pin this somewhere! i too, suck at organisation...

TeresaT said:

So, all you sciency peeps: Tell me why my logic (as well as math) sux and why I should not do it this way. Go ahead. Don't hold back. I can take it. I've got my "big girl panties" on.

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You could do it that way. As long as you keep the same lye concentration, you will always get the same lye discount when you replace a given percentage of water with vinegar.

If you make pure coconut oil soap with no lye discount to wash your big girl panties with, and you use a 33% lye concentration, you'll discover with the help of Soapcalc and a little arithmetic that you effectively get a 7.2% lye discount.

Make a pure castile soap while your panties are going around in the wash and the NaOH and water amounts will be very different because of the SAP value. However, as long as you use the same 33% lye concentration and replace all the water, your effective lye discount will end up being 7.2%

So if you plugged in no superfat and replaced all the water with vinegar, or even half of it, you'd be fine. If you use a different lye concentration, we have to figure out what the numbers are. It sounds like you already did, but not all your numbers could be right because, for instance, replacing half the water should result in half the lye discount. In the case of the 33% lye concentration, it comes out like this:

100% vinegar = (1 x 7.2) = 7.2% discount (as above)
75% vinegar = (.75 x 7.2) = 5.4% discount
50% vinegar = (.5 x 7.2) = 3.6% discount (half)
25% vinegar - (.25 x 7.2) = 1.8% discount

I prefer "lye discount" over "superfat", but we're both talking about the same thing.

topofmurrayhill said:

Multiply your oil amount by the percentage you chose:
2% of 500 g oil is 500 x .02 = 10

Multiply the result by 14.6 for the amount of vinegar to use in place of water:
10 * 14.6 = 146 g vinegar

Multiply the result by .49 for the amount of extra sodium hydroxide to add to the amount your lye calculator gave you:
10 x .49 = 4.9 g extra NaOH

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Sorry, i'm lost at step 3, multiply the result by .49? 10*.49 or 146*.49? I'm determined to get organised so in the midst of jotting this down in my excel file

apples said:

Sorry, i'm lost at step 3, multiply the result by .49? 10*.49 or 146*.49? I'm determined to get organised so in the midst of jotting this down in my excel file

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I went back and hopefully made it more clear.

Interesting post... I probably missed this discussed in another post (sorry if so), but I'm curious....

How does using sodium acetate compare to using sodium lactate? Other than cost and convenience, what are the alphas/deltas to using one over the other?

I don't sell, but like to think of all possible aspects and can see the sodium acetate being a clear loser in label appeal - depending on market. I suppose "vinegar" could be listed instead - that sounds even better than "sodium lactate" though. So maybe that point is a wash.

Perhaps this is outside the scope of this post, but I use SL in some B&B formulations as an alternative humectant to glycerin. Now, I'm a pretty big noobie when it comes to B&B, but I'm wondering about the ingredient in that arena.

snappyllama said:

Interesting post... I probably missed this discussed in another post (sorry if so), but I'm curious....

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Speaking of missing things, here are some past threads for your reference or for anyone else who needs them, plus a link to the 100 year old patent for hardening soap with sodium acetate or sodium lactate.

http://www.soapmakingforum.com/showthread.php?t=57991
http://www.soapmakingforum.com/showthread.php?t=59148
http://www.soapmakingforum.com/showthread.php?t=59092
https://docs.google.com/viewer?url=p.../US1377843.pdf

snappyllama said:

How does using sodium acetate compare to using sodium lactate? Other than cost and convenience, what are the alphas/deltas to using one over the other?

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Beyond cost and convenience, there's no significant difference between the two additives in the application that I tested them in. In terms of shortening and hardening soap, as well as increasing lather, the results are nearly identical and the additives are interchangeable. SA is an alternative for people who have wanted to use SL for this purpose in bar soap but can't easily buy it where they live.

If I can address cost and convenience for a moment, the biggest difference here is that you use only a 5% acetic acid solution to make sodium acetate, and the high usage rate for vinegar makes it a water replacement. People often would prefer to use a water replacement of their own. The fact that sodium lactate is typically purchased as a 60% solution allows for a more flexible and convenient usage rate.

snappyllama said:

I don't sell, but like to think of all possible aspects and can see the sodium acetate being a clear loser in label appeal - depending on market. I suppose "vinegar" could be listed instead - that sounds even better than "sodium lactate" though. So maybe that point is a wash.

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The way I look at it, sodium acetate and sodium lactate are equivalent in label impact. Depending on whether it's a problem, you would use either or neither of them. If people ask, they are both edible organic salts. You can use sodium acetate to make salt and vinegar potato chips.

As you point out, sodium acetate may have an advantage for people who list what goes into the pot as ingredients rather than what comes out. I don't suppose anyone will freak over vinegar, because obviously it's not made of chemicals. ;-)

snappyllama said:

Perhaps this is outside the scope of this post, but I use SL in some B&B formulations as an alternative humectant to glycerin. Now, I'm a pretty big noobie when it comes to B&B, but I'm wondering about the ingredient in that arena.

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I don't know for sure, but it's an interesting question. I do know that sodium lactate, potassium lactate and sodium acetate are sometimes used in the same applications, one of which would be packing and preserving meat. I believe that humectant properties are desirable in that application.

You have used sodium lactate as a humectant. I have used potassium lactate as a humectant in liquid soap with very good results. It would not surprise me if a sodium acetate solution had similar qualities, but I think it isn't soluble enough to make as concentrated a solution as 60% SL.

Thank you for this post.

I am going to try a water replacement with a recipe I have been contemplating. It has a low cleansing number which means it won't strip the natural oils as much BUT is too soft for my liking. I ran a similar recipe last week and it took 3 days to get it set enough to unmold.
Jan has willingly let me have a half gallon of 5% vinegar she had stashed.

Steve85569 said:

Thank you for this post.

I am going to try a water replacement with a recipe I have been contemplating. It has a low cleansing number which means it won't strip the natural oils as much BUT is too soft for my liking. I ran a similar recipe last week and it took 3 days to get it set enough to unmold.
Jan has willingly let me have a half gallon of 5% vinegar she had stashed.

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Sounds good. That's the classic application in soaping history -- making hard soap out of soft oils.

topofmurrayhill said:

You could do it that way. As long as you keep the same lye concentration, you will always get the same lye discount when you replace a given percentage of water with vinegar.

If you make pure coconut oil soap with no lye discount to wash your big girl panties with, and you use a 33% lye concentration, you'll discover with the help of Soapcalc and a little arithmetic that you effectively get a 7.2% lye discount.

Make a pure castile soap while your panties are going around in the wash and the NaOH and water amounts will be very different because of the SAP value. However, as long as you use the same 33% lye concentration and replace all the water, your effective lye discount will end up being 7.2%

So if you plugged in no superfat and replaced all the water with vinegar, or even half of it, you'd be fine. If you use a different lye concentration, we have to figure out what the numbers are. It sounds like you already did, but not all your numbers could be right because, for instance, replacing half the water should result in half the lye discount. In the case of the 33% lye concentration, it comes out like this:

100% vinegar = (1 x 7.2) = 7.2% discount (as above)
75% vinegar = (.75 x 7.2) = 5.4% discount
50% vinegar = (.5 x 7.2) = 3.6% discount (half)
25% vinegar - (.25 x 7.2) = 1.8% discount

I prefer "lye discount" over "superfat", but we're both talking about the same thing.

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You make me laugh. I thought my numbers looked odd. But, that was what I had written and I am certainly no math wiz. I was sitting at the table late one night bleary eyed plugging in various lye discounts for 1 pound of 100% OO and comparing the NaOH amounts needed for each one. Which is how I came up with the "safe soap" determination. No math true skills or scientific knowledge required. Just lots of coffee and the ability to do screenshots and write stuff down. However, even after cleaning off my dining room table this afternoon and sorting the junk that has been piled on it into "dogs," "soap," "knitting," and bills" I cannot find my ciphering (as a buddy calls anything higher than 1+1).

After all of that "figuring stuff out" I still have not made my trial OO soaps with the different percentages of ACV - which I went and bought specifically to do. I also want to try the experiment with nothing, with 2% salt and 2% SL as the hardeners to compare how long it takes to get them out of the mold, the hardness factor over the cure and what the cure times are.

My issue is I don't have a micro scale and have to make larger batches than I wanted to, four ounce batches instead of one ounce batches. When I'm making one or two pounds, I don't care if I round up or down. However, when I'm doing something so small, I thought it would be better to have as close to 0.567 gms of salt as possible. Using 1 gm would totally screw up the values. But I really don't want to make seven 4 oz batches of soap. I'm lazy. I probably could do the non salt/SL batches very small and just do those bigger. This isn't real science. This is just curiosity and trying to improve my product with the least amount of additional "chemicals" possible. Please forgive my babbling...

ETA: by the way, since I actually DO soap at 33.333%, I'm going to remember that 7.2 discount will be the "standard" discount I get when I soap with 100% vinegar and 0% SF on the SoapCalc dial. That will help me a lot when I'm deciding whether to do it at 0 or something else on the SoapCalc. Since I suck at math and am way too chicken, I wouldn't try this with any other concentration of lye. I didn't get to be 50 by doing stupid crap. (relatively speaking.)

Can I make this into my 50/50 lye masterbatch, using full vinegar and multiplying by .49 for the extra lye needed? Then using it as I do my regular 50/50 with the added in extra liquid? Sorry if this is a dumb question but the brain is not cooperating today. But then that is normal for me lately...

cmzaha said:

Can I make this into my 50/50 lye masterbatch, using full vinegar and multiplying by .49 for the extra lye needed? Then using it as I do my regular 50/50 with the added in extra liquid? Sorry if this is a dumb question but the brain is not cooperating today. But then that is normal for me lately...

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That's actually a really good question. I master batch my lye, too (2:1) and would benefit greatly if I could do it with vinegar instead of water. Come to think of it, it would be cool to master batch with beer, too. But I don't think that's possible. I think the beer would mold.

TeresaT said:

My issue is I don't have a micro scale and have to make larger batches than I wanted to, four ounce batches instead of one ounce batches. When I'm making one or two pounds, I don't care if I round up or down. However, when I'm doing something so small, I thought it would be better to have as close to 0.567 gms of salt as possible. Using 1 gm would totally screw up the values. But I really don't want to make seven 4 oz batches of soap.

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Wow those are some small test batches, especially when you're testing additives that would be used in small amounts. I can be pretty badass sometimes, but I normally make testers with 8 oz oils. And I have this:

So what is the difference in using salt instead of Sodium acetate or sodium lactate for making a harder bar of soap?

cmzaha said:

Can I make this into my 50/50 lye masterbatch, using full vinegar and multiplying by .49 for the extra lye needed? Then using it as I do my regular 50/50 with the added in extra liquid? Sorry if this is a dumb question but the brain is not cooperating today. But then that is normal for me lately...

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I wouldn't go masterbatching until we have more experience with this technique. At least you should make some small solutions and sit them on a shelf for a while to see what happens. But yes I would think you could do it if you're willing to do some more figuring and experimentation. Vinegar is only 95% water plus the H2O produced in the chemical reaction. You'd have to account for this when considering a 50% concentration. We also don't know how the sodium acetate affects how much NaOH it will be possible to dissolve.

Another issue with larger scale production is that we don't know much about nature of the water used to make vinegar. Might be a good idea to use EDTA until we can find out if the water is distilled or just purified tap water or whatever.

topofmurrayhill said:

Wow those are some small test batches, especially when you're testing additives that would be used in small amounts. I can be pretty badass sometimes, but I normally make testers with 8 oz oils. And I have this:

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That is beautiful! What's the maximum weight it holds? What kind? Where'd you get it? I was looking at some yesterday (or Thursday) and they're a couple hundred dollars up to thousands. So far my problem with test batches is they've all been for recipes and I've done 2 lbs testers. I don't have small mold, although I just got two 1# and two 11 oz "guest" molds from Crafter's Choice yesterday. I do have bar molds, but I just thought about them now as I was going through the stuff in my mind. I always use my loaf molds for some reason...

Swampy said:

So what is the difference in using salt instead of Sodium acetate or sodium lactate for making a harder bar of soap?

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Someone was interested in doing the experiment and telling us what the difference is between various hardening additives. I don't use salt so I don't know the answer to your question. I only know that lactate and acetate produce very similar results.