Best way and time to add stearic acid to harden soap

[Oxbow]

Hello,
I want to harden my soap and read here stearic acid can be a good solution, I finally found it and bought it. It is very affordable.

People say that the problem is, when they add this acid to the mixture, it turn the whole mixture solid instantly.

To avoid that I will try something : to melt the stearic acid in a cooking pan, then to add it hot juste before the trace.

So yeah my mixture will heat a bit but I don't see any problem here to do that, and this solve the problem of the "instant saponification" of the acid.

The goal is to reach the real trace without the stearic acid causing a "fake trace", and to end up with a solide soap. What do you think ?

 

[DeeAnna]

"...melt the stearic acid in a cooking pan, then to add it hot juste before the trace ..."

That's a valid way to add stearic acid, but this method will not slow down the reaction of stearic acid with the lye. You can only control the time at which this reaction happens.

Stearic acid will not create a "fake trace". When it reacts with lye to thicken the soap, the soap will stay thick.

The amount of stearic acid you plan to use will also make a difference.

If you are adding a few percent of stearic acid to make a bath soap, you should be able to make the soap using a cold process method without too much trouble.

If you are adding a lot of stearic to make a cream or shaving soap, you must use a hot process method -- cold process will not work.

 

[GemstonePony]

"...melt the stearic acid in a cooking pan, then to add it hot juste before the trace ..."

That's a valid way to add stearic acid, but this method will not slow down the reaction of stearic acid with the lye. You can only control the time at which this reaction happens.

Stearic acid will not create a "fake trace". When it reacts with lye to thicken the soap, the soap will stay thick.

The amount of stearic acid you plan to use will also make a difference.

If you are adding a few percent of stearic acid to make a bath soap, you should be able to make the soap using a cold process method without too much trouble.

If you are adding a lot of stearic to make a cream or shaving soap, you must use a hot process method -- cold process will not work.

Oh good, I was about to tag you in my reply anyways, because it didn't make sense to me that it wouldn't be melted in with the oils as a small percentage of a well-balanced recipe.
ETA: I use Stearic Acid primarily in lotion balm, body butter, and the like, and mine is a pain to melt without a liquid present.

 

[DeeAnna]

From what I see here, I think most people melt the stearic and fats all together, add the lye, and stir mostly or all by hand until the stearic has done its thing.

I like to start a batch with just the fats only, get the soap batter to trace, pour the melted stearic into the soap batter in one fast pour, and then hand stir from there. Just my personal preference. I do pine tar soap this way as well -- mix the pine tar with some of the fats, add the lye to rest of the fats and bring that to trace, and then hand stir the pine tar and oil mixture into the soap batter.

If you're doing something like I do, it's certainly a good idea to add some fat to the stearic to help the stearic melt a little easier.

 

[lsg]

I melt stearic acid with my hard fats and then add the liquid oils. You do have to work quickly after adding the lye solution to your fat and oil blend.

 

[amd]

I use stearic acid in my honey soaps - they tend to be softer soaps and I found the stearic gives them a nice hardness. I did several experimental batches to see where I could notice 1) that the stearic is adding hardness to the soap and 2) where it affects the acceleration of the soap. *Keep in my mind my oil blend tends to move into trace very quickly to begin with, I don't have a lot of working time, so your results may vary*

I did 0.5%, 1%, 2% and 5% of my oils as stearic acid. What I found:
0.5% no discernable difference (no big shock) to anything
1% gives a nice hardness and mild fluffy lather
2% was not a discernable difference in hardness, lather a bit more fluffy
5% a lot of hardness, more fluffy lather, but my soap accelerated considerably

A few notes on my testing: My "hardness" test was judged by how much give I could feel in the bar 24 hours after making. My honey soap without stearic (BS if you will, ha!) will leave a considerable dent when pressed with my thumb. Lather notes were made after approx 6 weeks cure time. No fragrances were used in the tests, although I did color each batch differently to make sure I could keep them straight.

Based on my results and what I wanted to achieve, I use 1% stearic acid. At that low amount I find that I can melt it easily in the microwave and add it to my oils right before adding my lye solution. I don't have any problems (or, erm, any more than usual) with acceleration and have been able to do hanger swirls, ITPS, and drop swirls with this recipe.

 

[Oxbow]

Thanks a lot for the replies,
@amd from what you say, I will go with 1% of the oil and solid fat. Technically, if I use 1% of stearic acid in all my soaps, the stearic acid will cost me 5 times less than if I use it at 5%.
Also, to harden the soap I will try putting less water, more NaOH and more solid fats (cocoa butter, coconut oil, beef tallow (I am not vegan sorry if I shock somebody)), and olive oil that becomes very hard if you cure it well, from what I have heard.

 

[Murage]

Stearic acid mainly depends on what you want to achieve.
I personally use 3.5% of total oils when making soap.
And 1.5% total weight of all ingredients in lotion making. And i find it working well

 

[SoapMedic]

thank you this is helpful for me, I think in my few attempts with stearic I used too much with poor results. I stick to adding sodium lactate now and that has worked really well for me and been super easy.

 

[DeeAnna]

Sodium lactate and stearic acid do different things, so you can't use them interchangeably.

Yes, they both add physical hardness to the soap. Stearic acid also adds longevity to the soap because stearic soap is not very soluble in water. Sodium lactate does not greatly change the longevity of soap.

So if you're having problems with your soap not lasting long enough in the bath, you're going to be better off increasing the stearic acid content in your soap rather than using sodium lactate.

Increasing the stearic acid content can be done by adding stearic acid, but it can also be done by increasing the percentage of fats high in this fatty acid -- lard, tallow, palm oil, soy wax (hydrogenated soy oil), and the butters such as cocoa butter. Using high-stearic fats eliminates the problem of having to melt the stearic acid and having to soap at higher temperatures.

But sometimes using stearic acid is the best solution, as when making shave soap.