by PureNature March 14, 2017
There has been a resurgence of interest in water in oil (w/o) emulsions because of their innate ability to provide better moisture protection than most standard oil in water (o/w) emulsions. In the past, w/o emulsions lost favour because they either needed to be created using mostly silicones, silicone derivatives or mineral oils to feel nice; otherwise they would leave a heavy, greasy residue when created with natural materials. However, with the ever-increasing choice of naturally derived esters, w/o emulsifiers and w/o emulsion stabilisers, more elegant emulsions can now be created with a relatively high natural ingredient content.
A water in oil emulsion is one where the continuous phase is oil or lipid based and the internal (dispersed) phase is water. In order to create and stabilise a w/o emulsion:
Here is a diagram to illustrate how this works – picture that the white space around the droplets is oil; the blue droplets are water; the ‘sticks’ are the correctly selected emulsifiers and the blue lines are the correctly selected polymer:
To stabilise these types of emulsions, emulsifiers must have a low HLB value (hydrophile/lipophile balance), ideally around 3-5. For those of you who aren’t familiar with this terminology, look for emulsifiers and blends that specifically state they are good to create w/o emulsions – this takes the guess work out of selection for you.
The right type of polymer will be ‘oil compatible’ or ‘oil soluble’. AVOID water soluble/compatible polymers like xanthan gum and carbomers – they are the worst possible choice and will pull water droplets together leading to rapid destabilisation!
You may also like to consider lecithin, as it is also well suited to these types of formulations and imparts a beautifully cushiony skin feel. You can this in w/o emulsions between 1 – 5% for aesthetic purposes but it is not sufficient on its own to be the main emulsifiers.
Combine your oil phase materials, emulsifiers and polymer together and heat until all melted; add equally hot water to this phase; and then homogenise. Allow to cool and then add suitable preservatives, antioxidants and other extras (fragrance, extracts etc) as required.
Finally, don’t be fooled into thinking that these products don’t contain enough water to need preservation – they most certainly do! Make sure you are selecting a broad spectrum preservative that is compatible over a broad pH range for the most effective protection.
Now, enjoy the fantastic moisture protection these products can provide while you play with the sensorial aspects for best results…Happy formulating!
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