With so many unstable recipes available, it’s no wonder many lotions fail to emulsify or stay emulsified.
Important: Beeswax and cetyl alcohol are NOT emulsifiers.
Emulsifiers vary greatly – some work really well and some are less effective. Check the supplier’s website for the inci name of the ingredients which make up the emulsifier. For an emulsifier described as “self emulsifying” to have a chance at performing as such, it should consist of at least two separate emulsifiers.
Which emulsifier should a newbie buy? The following are reliable blends and make for a good starting point: Polawax NF or a blend of cetearyl alcohol plus polysorbate 60 or, for a natural emulsifier, Natragem EW is sold by Penny Lane Organics in Canada and in Europe it’s sold as “Ecomuls” (not to be confused with Ecomulse) by behawe.com, hobby-kosmetik.de or rosarome.de. If you have oily skin, lotionpro or lexemul is a good choice. There are lots of other emulsifiers available, for example, liquid crystal emulsifiers, such as olivem and cetearyl glucoside have their own quirks so maybe a bit tricky for a newbie. If you are intending to use emulsifiers not listed here do conduct a search of the inci name to see the original supplier’s data sheet so you can get to know it’s processing requirements and suitability.
How much to use?
For Polawax NF and cetearyl alcohol + polysorbate 60 and Natragem EW, a starting guide is to add it at 25% (one quarter) of the total of the oil soluble ingredients in your recipe. (Note: Oil soluble ingredients can also be found in your cool down phase, for example, fragrance, vitamin E, cyclomethicone). So if your oil soluble ingredients excluding the emulsifier totals 10% then you’ll be using 2.5% emulsifier. Lotionpro/lexemul is more effective at low levels than polawax so can be added at only 15% of the total oil soluble ingredients instead of 25% but do not add it below 3% in your recipe. It is quite a “thin” emulsifier so you’ll need to add an extra 2% cetyl alcohol. For other emulsifiers, do check the supplier’s data sheet for information on how much to add. If you cannot find this information, start with this 25% guide rule.
If your lotion contains a high oil phase (eg over 27%), I find this 25% rule often isn’t a linear relationship. In these circumstances, it’s best to only use enough emulsifier to do the job – too much could end up causing your lotion to be draggy/soapy.
Don’t forget to add a stabiliser to your lotion (see this article for more information on stabilisers and how to make your product more stable: http://www.makingskincare.com/emulsions-stability/)
Also, don’t forget to use a stick blender rather than a coffee frother/whisk, otherwise your lotion may not stay emulsified!!
Once you’ve a few lotions under your belt you might wish to try other emulsifiers, and even create your own blend. Here’s a calculator which will walk you through the HLB system.