A carbomer gel

There aren’t a huge number of raw materials developed specifically to fulfill a need in personal care.  Most things that go into your cosmetics and toiletries were originally intended for another purpose altogether and got pressed into service by formulators.  But carbomer was always intended for skin products.  It has subsequently been used by other industries but it was ours to begin with.

Carbomer was first launched in the nineteen fifties, rapidly became a huge hit and by the middle of the sixties no cosmetic lab would have been without a jar of the fluffy white powder.  It has retained this position ever since, despite the best efforts of the company that first created it and all their competitors to try and improve on it.  So what is it?  It doesn’t really do it justice to just call it a thickener.  There are plenty of ways to thicken something up.  But carbomer not only gives you the viscosity you want, it also stabilises your formulation and gives it texture.  By varying the level and the exact way you use it you can use carbomer as a base to create anything from a stiff hair gel that will stay exactly where you put it, a lotion with body but which still flows easily or a rich cream that holds it shape.

Carbomer Neutralisation

If you look at an ingredient list, if you see carbomer listed you will almost always see either sodium hydroxide or triethanolamine listed as well.  These are neutralising agents used to neutralise the carbomer.   Somebody in a lab somewhere will have thought through which neutralising agent at which level would suit the needs of the product best.  If he or she has done their job well you should have a product whose look and feel make the product a joy to use.

Nearly as important as what it does is what it doesn’t do.  It doesn’t seem to have any effect on the skin at all. If you rub a neat carbomer gel into your skin, once it has dried you don’t notice it.  It doesn’t make your skin tacky.  It doesn’t make it feel tight.  You just don’t notice it.   It isn’t there to give any benefits, just to make the formulation elegant and enjoyable.

Carbomer Chemistry

The chemistry of carbomer is totally synthetic and bears no relationship to anything in nature.  This is a good thing.  It means that your immune system has not encountered anything similar in its evolutionary history and so it is unlikely to react to it.  There are millions of people in the world of course, and I dare say there are some of them somewhere who do react to carbomer.  Whatever you use there is somebody somewhere who will react to it.  But I have never come across or heard of a reaction to this particular material.

Carbomer poses no safety concerns.  The Skin Deep database gives it a zero risk, though does give it a 97% data gap.  I am not sure how they work that one out, as there is plenty of data.  It is listed in several pharmaceutical national formularies so it is considered good enough for pharmaceutical use.   There is one UK company I know of that uses carbomer free as a marketing claim.  But even they only object to it on the basis that is a petrochemical derivative, which is true enough.

The only people who have a problem with carbomer are the organic sector.  Carbomer is not specifically banned by the Soil Association, but they do require that natural thickeners be used when they are suitable.  They usually are though they aren’t as good.  I think this is probably the single biggest reason why organic products often seem a bit rubbish compared to conventional ones.  They do the job just as well, potentially at any rate, but they just lack the elegance that can be achieved with carbomer.  But that presumably is a choice that the people who seek out those kinds of products have made.

I don’t think it is an exaggeration to say that the texture of modern cosmetics have been profoundly changed by this interesting ingredient.  Next time you use a product, in particular a lotion, put a drop on your finger and look at the shape.  You should be able to make a good impression of Frenchman’s beret.  This is the texture you associate with carbomer.  It is possible to achieve it in other ways, but it is really easy with carbomer.   The beauty of of it is that it is firm enough to only go where you want it to go, but soft enough to be easy to rub in.  It isn’t perhaps as spectacular as some of the achievements of science, but it is one that you can see in any bathroom around the world.  And now you know how its done.

If you are looking for a more natural thickener, have a look at my post on xanthan gum.



Notes on Carbomer for Chemists

There are naturally a lot of different grades of carbomer with different CAS numbers i.e.,  9007-20-9, 9003-01-4 , 76050-42-5 , 9062-04-8 , 9007-16-3  or 9007-17-4 but all are listed on the pack simply as carbomer.  The chemistry is relatively simple to describe but can have interesting ramifications.  The backbone of the polymer is made up of acrylic acid monomers with enough acid groups left unreacted for the overall  polymer to be acidic.  Sugar groups are substituted onto it to give desired level of solubility.

Before it is neutralised the polymer chain fills the space relatively poorly.  Once it is neutralised the volume occupied by the polymer expands enormously thickening up the formulation.  Judicious choice of polymer concentration and degree of neutralisation gives you a lot of control over the rheology of the final product.  One other feature of carbomer that is worth remembering is that it is the salt of a weak acid and so has a pretty good buffering effect.  This can be good or bad depending on what you are trying to achieve, but is unavoidable.

The other feature that really cannot be ignored is that it is very shear sensitive, so you will lose structure if you knock it around too much.  I once talked to a skilled rheologist who was able to detect the loss of viscosty in a carbomer gel if it was simply pumped through a pipe with a corner in it.  On a more practical level, you need to keep control of the manufacturing process pretty nicely or every batch will come out different.  Whatever other properties your product does or doesn’t have, variety is one that you don’t want.

(For worthy but dull safety information etc see the cosmetics info entry .)

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