Adjusting Emulsion Viscosity
How to make your emulsion thicker or thinner.
First analyze your formula to see what ingredients are contributing to viscosity. This is usually the emulsifier blend, gums/polymers and any fatty alcohols/acids (stearic acid, cetyl alcohol, cetearyl alcohol) or waxes in your formula.
If you wish to make your emulsion thinner, all these ingredients listed above also provide stability so do be careful not to reduce the concentrations by too much if you are to avoid emulsion destabilisation. The following web page provides the information you need to calculate the minimum amounts of emulsifiers and stabilisers you need: http://makingskincare.com/emulsions-stability/
To reduce viscosity, you can also swap out your emulsifier blend for one which is thinner, such as TEGO® Care PBS6 or the pair up these single emulsifiers: TEGO® Care CG 90 with TEGO® Care PS.
Note: If your emulsion turns out much thinner than expected, bear in mind some ingredients can thin emulsions, such as urea or caprylyl glycol so you may wish to reduce the concentrations of those ingredients or add more thickener to compensate.
If you would like to make your product thicker and have only just made your emulsion, wait a couple of days before assessing the viscosity. If your emulsion is still thinner than you would like, adjust your next formula to increase the level of fatty alcohols/acid by 0.5-2%. This will also make your product slightly more heavy, draggy and creamy. If you wish to avoid this you add a water phase gelling agent, such as 0.5%-1.5% sclerotium gum or siligel™ instead.