Well here is a challenge. Can I write an interesting post about a very basic raw material? Glyceryl stearate is one of the names you will see cropping up on ingredient lists pretty often, especially for creams. I always call it glyceryl monstearate but its official name is glyceryl stearate. What is it?
Well it isn’t controversial. I don’t recall anyone claiming it is dangerous, which is nice. Another thing it isn’t is synthetic. It can be derived from most vegetable oils easily enough. You take a a couple of fatty chains off of a triglyceride oil and there you have it. So if you think of a natural oil as being a glycerin backbone with three fatty chains attached to it, you can think of glyceryl monostearate as a glycerin backbone with just one fatty chain attached.
Glyceryl Stearate is Green
If someone came up with it today, it would no doubt be hailed as a fine example of green technology. You make it simply by hydrolysing a suitable oil feedstock. This is a process not much more complex than making soap, which people can manage in their kitchens without too much trouble. It uses renewable resources and is not energy intensive. And the product itself is not toxic and is readily biodegradable. In fact biodegradation can be achieved not only by micro-organisms but by humans. The process of breaking down a triglyceride into its component parts is a very basic one that is one of the body’s major sources of energy and is going on in your cells right now. If you put a product containing glyceryl monostearate onto your skin I doubt that very much would get through to your bloodstream, but if it did the body would know exactly what to do with it once it got there.
Glyceryl Stearate – A Cousin of Soap
Cleaving the fatty chains off the glycerol gives us a cheap but really useful ingredient. The glycerin bit is water soluble and the fat chain is oil soluble giving you a molecule that can stabilise emulsions.
I said that the production process was similar to soap making. For the most popular form of glyceryl monostearate it actually involves a bit of soap making. By putting a splash of sodium and/or potassium hydroxide in the mix a small amount of soap is formed in addition. (For fellow chemists and the many soap makers out there, the soap is formed by neutralising leftover stearic acid. I find this really neat.) This is handy because the glyceryl monostearate alone isn’t that good as an emulsifier on its own. The soap enhances it considerably. It makes it into the grade known as Glyceryl Stearate Self Emulsifying. You will often see Glyceryl Stearate SE on an ingredient list, particularly in skin creams. This means that there is a trace of soap in there as well.
There is a great deal more I could write about this stuff, but I have probably already exhausted your patience.
If you enjoy ingredient posts have a look at my Cosmetic Ingredient Database
Notes for Chemists on Glyceryl Stearate
All the grades of glyceryl monostearate tend to get called GMS. The most widely used grade is the self emulsifying version with the official ICID name of Glyceryl Stearate SE and with CAS number 11099-07-3 and EINECS number 234-325-6. It is listed on the Cos Ing database and the SCCS have never troubled to express any opinions about it.
Even the easily spooked guys over at the Environmental Working Group can’t get very worked up about it giving it a zero hazard rating. They do moan about a 93% data gap. I don’t know how the data gap is worked out but it is hard to imagine that there is any particular shortage of information on such a well known material. In particular, given that we eat it daily it would seem a little pointless to feed it to laboratory animals to assess its toxicity – its safety really is beyond any doubt.
Other cosmetic ingredients that get used a lot in skin creams you might be interested in are cetearyl alcohol and isopropyl myristate.
And you might also be interested in the cosmetics.info monograph.
Always good to be reminded of past learning and then learn something new thank you
I
Suppose I have a mixture of beeswax and mineral oil. Now I want to make this mixture creamy. Can I just add water and glyceryl monostearate to it and stir? Thanks for your advice first.
Hi Fred, you can make a very nice night cream or barrier cream using just beeswax, mineral oil, glyceryl monostearate and some water. You will need a preservative as well. You won’t be able to create it just by stirring though – the method of manufacture is a bit involved. I wouldn’t particularly recommend doing it at home unless you are planning to devote a reasonable amount of time to the project.
Colin,
Oh, really thanks for your advice. Originally I thought that any emulsifier would mix water and oil easily.
So, can you suggest other emulsifying agents that could do the job easily? For example, can Polysorbate 20 do the job well?
In addition, I have heard that beeswax itself is an emulsifier. So can I just add water to the beeswax and oil mixture and then stir it?
As for preservatives, that’s exactly what I want to ask. What kind of preservative do you suggest?
Thank you very much!
(N.B. actually I am contemplating of making a Brylcreem-like substance for my hair).
Although it’s harmless for most people, I’m allergic to glyceryl stearate (I break out in hives when it gets on my skin), which is terribly inconvenient since it’s such a common ingredient in sunblock, lotion, and soap. It causes a burning sensation initially, then I get hives, and I have to scrub off the lotion or whatever caused the reaction, otherwise I break out in hives off and on for the rest of the day. It’s especially annoying when the only soap in a bathroom is stuff I have to rinse off immediately to avoid getting a reaction.
That’s bad news Rin, as you have discovered it is really widely used not just in cosmetics but in food as well. One suggestion if you haven’t already tried it, how about using a mineral oil rich cream like Oilatum or Diprobase (names may differ outside UK) to see if you can create a protective film to keep your skin protected from the allergen. Its a bit of a theoretical suggestion and I don’t know how well it might work.
Colin,
Thanks for this great article. I would like to try making GMS.
Does it involve just heating glycerine and stearic acid ( in the correct proportions of course) and letting it solidify?
Many thanks in advance.
I never expected to get a reaction like that one Ken!
I suppose you could make glyceryl monostearate by esterifying glycerine and stearic acid. That isn’t the way it is usually made though. It is formed by the partial hydrolysis of a triglyceride with stearic acid being liberated in the form of soap, so it is basically a special form of saponification where you only partially split the oil and produce a lot less soap than normal. I can’t advice on the details I am afraid. I get mine from companies that have been doing it for a decade and have got it down to a fine art.