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W/Si emulsions
I am new to formulating w/si emulsions (and w/o emulsions for that matter). Can you please give me general formulation advice? I know I need a salt/electrolyte for stability and a w/si emulsifier. I know the water phase must be added VERY slowly. As far as troubleshooting to increase viscosity or emulsion stability though, I am not sure where to start. Hoping there are some general rules of thumb like there are for traditional o/w emulsions.
Thanks!
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4 Replies
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W-in Si oil emulsions do not test well in classic preservative tests - failure does NOT mean they are susceptible. Strongly recommend you get a copy of the article cited below.
Schnittger, S., Sabourin, J. and King, D., 2002. Preservation of water-in-silicone emulsions. JOURNAL OF COSMETIC SCIENCE, 53(1), pp.78-80.
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As you said, 1-1.5% of salt (check the supplier of your emulsifier as they recommend different salts for different emulsifiers), you must have some stabiliser in oil (or in your case silicone) phase. It can be magnesium stearate, zinc stearate, hydrogenated castor oil, or for cold process something like covasilic 15 or silica. Amount of water depends on emulsifier and it’s important to follow recommendations of the supplier. Abil EM90 for example doesn’t tolerate high oil phase although it sounds counterintuitive. Success highly depends on your emulsifier. I would say Dow Corning’s formulation aid 5225 is relatively easygoing one. Abil EM90 is very unpredictable (although I like it). DowSil ES 5600 is quite nice as well. DowSil ES 5300 has nicer texture but it separates relatively easily (or I couldn’t find my way around it yet). Also never use one emulsifier, pair it with some w/o emulsifier at a lower %. Say, if I am using 2-3% of ES 5600 I would throw 0.5-07% of Isolan GPS or Cithrol DPHS. Add water by drops and only after emulsion has formed apply high shear.
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In most cases viscosity will increase as you apply high shear btw. It’s quite fascinating how runny liquid turns into a thick cream. It also adds to stability because size of particles descrease.
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Thanks for the comments, I was able to teach myself many things after making this batch with different variations about 12 times
I finally have a very stable, aesthetically pleasing version that I can recreate confidently.
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