Of Stearic Acids and Idiosyncracies

Okay so first I should say I have this problem. If you can’t or don’t understand this part then you probably won’t understand why I ask the rest: I am absolutely ate up with accurate measures and ingredients. I want to absolutely be able to reproduce what I do right, and of course avoid what I do wrong. I won’t add 500 g of this and a teaspoon of that because a teaspoon is not a measure it’s a stir stick.

So to my issue … Stearic Acid. I have a bag I have been using for some time and I found out to my horror that I do not know if it is actually stearic acid (CAS 57-11-4), stearin (CAS 555-43-1), or some mixed fats called “stearic acid” (CAS 67701-03-05) that’s actually a mix of stearic and palmitic acids. It was purchased for an application in the past where this was not important; now it is. So, question number 1: How can I tell which one it is?

Question #2: Does anyone have a reasonably priced source of real stearic acid they want to share? The typical suppliers which cater to soap and candle makers either seem to have that mixed stearic/palmitic flake product, or no information at all (and blank stares when I ask).

I can answer question #2. The place I buy my lotion-making supplies (Lotioncrafter's) sells the stearic acid you are looking for (CASRN 57-11-4), at what I think is a very reasonable price (at least pre-shipping anyway): http://www.lotioncrafter.com/stearic-acid-nf.html The have a full MSDS & Tech Data page on it that you can click on from the link I just posted.


IrishLass

Thanks IL!

The solution is to get a product that has a confirmed analysis. Short of sending your current "stearic acid" to a chem lab for analysis, there's not a good way to determine exactly what it is. You could look perhaps at melt points or densities, but the answers you will get from these tests are not ones I think you would be willing to live with. Better to just start fresh.

Yeah I was hoping that someone would say "oh add two drops of X and see if it fizzles" or something easy.

The densities are close enough to make it challenging but I may try that.

But is a drop an acceptable measure?

Touché!

Another thing to think about is you're able to get fully hydrogenated tallow (or lard). I suppose you could try hydrogenating the stuff yourself, but messing with hydrogen can be a bit hazardous.

On an aside, after the last time I posted about this I postulated that fully hydrogenated castor oil might also work well. Turns out you can buy the stuff ... thread here.

-Dave

I know exactly where my tallow comes from and exactly what it is thankfully. It comes direct from a family farm from ranged cattle. I do not use hydrogenated and I'm happy with the result. For my bar soaps I use both hydrogenated and non-hydrogenated lard. I struggle to tell a difference in a blind test, but the lard is not the predominant ingredient.

dosco said:

Another thing to think about is you're able to get fully hydrogenated tallow (or lard). I suppose you could try hydrogenating the stuff yourself, but messing with hydrogen can be a bit hazardous.

On an aside, after the last time I posted about this I postulated that fully hydrogenated castor oil might also work well. Turns out you can buy the stuff ... thread here.

-Dave

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I haven't seen fully hydrogenated tallow sold anyplace but you'd still have the palmitic, mysristic and lauric acids after hydrogenation. Soy oil comes out around 87% stearic after hydrogenation and is often sold as "soy wax" (but when I have seen it sold it's more than the same sellers price for straight pressed vegetable sourced stearic.

Anybody got the scoop on Soapers Choice Stearic?

I have emailed Soapers Choice about this a couple of times and not heard back. May call them.

IrishLass said:

I can answer question #2. The place I buy my lotion-making supplies (Lotioncrafter's) sells the stearic acid you are looking for (CASRN 57-11-4), at what I think is a very reasonable price (at least pre-shipping anyway): http://www.lotioncrafter.com/stearic-acid-nf.html The have a full MSDS & Tech Data page on it that you can click on from the link I just posted.


IrishLass

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DeeAnna said:

The solution is to get a product that has a confirmed analysis. Short of sending your current "stearic acid" to a chem lab for analysis, there's not a good way to determine exactly what it is. You could look perhaps at melt points or densities, but the answers you will get from these tests are not ones I think you would be willing to live with. Better to just start fresh.

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boyago said:

I haven't seen fully hydrogenated tallow sold anyplace but you'd still have the palmitic, mysristic and lauric acids after hydrogenation. Soy oil comes out around 87% stearic after hydrogenation and is often sold as "soy wax" (but when I have seen it sold it's more than the same sellers price for straight pressed vegetable sourced stearic.

Anybody got the scoop on Soapers Choice Stearic?

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Or Essential Depot?

If you really want a ingredients with a confirmed, consistent chem analysis, then go to the chemical supply houses and look for reagent grade chemicals. Places like Soapers Choice or ED are not in that business niche -- they are just not going to carry 99% stearic or whatever.

The listing at SC is for "vegetable stearic" which is going to be a blend of palmitic and stearic fatty acids harvested from veg oil -- probably palm. You're going to get whatever % of stearic happens to be in the veg oil at the time.

I don't see the need for this type of purity for soap making ingredients, but I do know the difference between commercial and reagent grade chemicals. If you want the higher purity, consistent stuff, then you'll need to go to the sources that actually carry it ... and expect to pay the price.

I don't have an issue with "craft grade" chemicals. I just want to know what it is. Being a few % back and forth between Palmitic and Stearic is one thing, and I can always choose to buy the discrete acids if I want exact. Not even knowing if I'm using Palmitic is different in my mind.

DeeAnna said:

If you really want a ingredients with a confirmed, consistent chem analysis, then go to the chemical supply houses and look for reagent grade chemicals. Places like Soapers Choice or ED are not in that business niche -- they are just not going to carry 99% stearic or whatever.

The listing at SC is for "vegetable stearic" which is going to be a blend of palmitic and stearic fatty acids harvested from veg oil -- probably palm. You're going to get whatever % of stearic happens to be in the veg oil at the time.

I don't see the need for this type of purity for soap making ingredients, but I do know the difference between commercial and reagent grade chemicals. If you want the higher purity, consistent stuff, then you'll need to go to the sources that actually carry it ... and expect to pay the price.

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When people speak of the mix of pamitic in the stearic from soap suppliers is this just the pamitic that happened to make it through the pressings? Is it an insignificant amount from a soaping POV or is this a situation where the product is consciously delivered with a mix?

boyago said:

When people speak of the mix of pamitic in the stearic from soap suppliers is this just the pamitic that happened to make it through the pressings? Is it an insignificant amount from a soaping POV or is this a situation where the product is consciously delivered with a mix?

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Good question. I know the mixture is more than just a trace of palmitic. Sigma-Aldrich lists it as a "mixture of fatty acids, consisting mainly of stearic acid and 40-60% palmitic acid."

Lee is correct -- commercial stearic acid contains a very high % of palmitic. My rough rule of thumb is to assume a 50:50 mix, but the actual ratio of palmitic acid to stearic acid will vary depending on the particular fat being used. The chemical composition of any given fat can vary quite a bit depending on the plant variety, the climate/weather, how the product is harvested, etc., so any fatty acids extracted from the fat will also vary accordingly.

Commercial stearic is created by cooling liquid palm oil (or lard or tallow, if an animal source is used) until the high melt point fats solidify. These fats are called "stearin" and they are the fats that contain the most stearic and palmitic acid. These solid fats are then filtered out of the liquid "olein" (fats that contain mostly oleic acid).

The stearin is then broken down into fatty acids probably by hydrolysis (the process of reacting the fats with steam under high pressure and temperature). The water soluble byproducts (mostly glycerin) from the hydrolysis are removed, leaving the fatty acid mixture. That's what you get when you purchase commercial stearic acid.

If you want a pure stearic acid, the commercial product has to be further purified to remove the palmitic acid. I'm not sure how that's done.

Thank you Deeanna.
So in while using a SAP calculator soapcalc in this instance (it's what I use) the stearic content when stearic acid is selected is 99% SA and Palmitic is 98% for more accurate values I should use 50/50 stearic and palmitic to get better values?

For those of you interested here is a paper on stearic acid production. The Author wasn't listed anywhere so thank you to who ever you are who wrote it. http://www.sbioinformatics.com/desi...ic-2520acid_Methods-2520of-2520Production.pdf
side note: The paper was probably written some time ago as I think (and others have mentioned) the feedstock for this process is more likely to be palm oil these days.

My email to Essentials Depot:

"I am learning from the Soap Making Forum that product labelled as Stearic Acid can be either pure SA (CAS number 57-11-4), stearin (555-43-1), or a mix of stearic and palmitic acids (66701-03-05). Can you please confirm which kind you sell ?

Thank you very much"

Their response:

"Mr. *cpacamper*,

I can confirm that we offer the first one you mention, pure Stearic Acid.
Please let me know if you have further questions.

Reagrds,
Brittan

ESSENTIAL DEPOT, Inc."

Boyago -- Yes, that's the approach I would take when using commercial stearic.