Glyceryl stearate – home made emulsifier
Glyceryl stearate is a non-ionic low HLB emulsifier and emulsion stabilizer.
Because it has low HLB, for emulsions oil-in-water it is being used in combination with another emulsifier. It is said that it brings to creams and solutions a non-greasy, but rich touch.
As the majority of emulsifiers, it is an ester- or simply said, an organic compound derived from reaction of alcohol and carboxylic acid. Carboxylic acids are for example fatty acids found in oils and fats and therefore one can envisage making different emulsifiers at home simply by reacting an oil of choice with an alcohol of choice. Such an emulsifier is of course not going to be pure as are those of commerce – this is because we do esterify all the fatty acids in the oil, not only one. However, we create often an emulsifier with good qualities. Moreover, glyceryl stearate is easy to make pure, because we can buy pure stearic acid in online craft stores.
I was inspired by french bloggers that are making all kind of emulsifiers:
Glyceryl stearate is an ester of stearic acid and glycerol (AKA glycerin – yes, it is also an alcohol!). Because pure stearic acid is easy to find in soapmaking online stores, we can pretty easily make pure glyceryl stearate at home.
Reaction of carboxylic acid and alcohol is naturally very slow, therefore a catalyst is needed. Adding a solution of acid helps the reaction to take place more efficiently. The exact amount of acid is not important. Usually, we use citric acid or vinegar. Also, glycerine should be in excess, just to be sure there is enough to esterify all the stearic acid.
20 g stearic acid
20 g glycerine
40 g of vinegar or 20% solution of citric acid)
Melt stearic acid in glycerine in water bath, after the stearic acid is melted add your acid and heat for an hour.
During this time you will see glyceryle stearate – white parts – precipitating out of the solution and floating on the top, creating a solid layer.
After one hour let everything cool, you can use fridge, then extract the solid part – this is glyceryl stearate – and get rid of the liquid part – this is the rest of glycerol and acid citric and possible other compounds like glyceryl citrate for example that were created during the process.
Glyceryl stearate is solid, white and fragile. It is of interest to wash it in water just to get rid of all possible liquids. After it dries, we can break it into peaces and stock for next usage.