Friday, March 6, 2009

Surfactants & fragrancing - clarity

So what's the difference between this purple body wash (fragranced with Black Amber Lavender from Brambleberry) and the orange body wash (Cedar & Saffron, also from Brambleberry). They're both body wash made from the same batch of ingredients and bottled in identical bottles. So why is one cloudy, the other is clear?

This has to do with the polar nature of our ingredients. Polar means that it has a negative charge on one end and a positive charge on the other. Water is polar, and most of the surfactants are as well. Some fragrance oils are polar as well - the black amber lavender is polar, the cedar & saffron isn't. So when you mix the polar with the polar, you get a homogeneous mixture (meaning is has the same uniform composition and appearance throughout). When you mix polar with non-polar, you get a heterogeneous mixture, meaning it isn't the same uniform composition and appearance throughout, and it's cloudy.

It's not a bad thing to have cloudy surfactant mixtures, but some people get picky about the appearance. So what can you do to make clear products?
  • Use polysorbate 20 to emulsify the fragrance oil. Adding a little polysorbate 20 - about a 1:1 ratio - with your fragrance oil prior to adding to the body wash or bubble bath will keep it clear.
  • Choose polar fragrance oils. This may not be an option if you simply must have something like cedar & saffron in your surfactant mix or if you are using specific essential oils.
If you can't get it clear, then you can use a pearlizer like glycol distearate (EZ Pearl at Voyageur) to turn your mixture opaque. This does look pretty cool, but if you don't do it properly, you can end up with very thin, cloudy bubble bath with a white goop at the bottom of the bottle.

How to do it properly? Heat up your surfactant mixture without the water, and add the glycol distearate, stirring until it is melted. Then add your heated water (make sure you heat it first or the glycol distearate will clump up again - ask me I how I know this!!!) and the other ingredients until it is a uniform mixture. As it cools, add your heat sensitive ingredients and let cool completely before bottling. As EZ Pearl is an emulsifier and thickener, you will need to add less Crothix to this mixture and it will be slightly less foamy and/or lathery.

Get some cyclomethicone and put a small amount in a shot glass. Now add your fragrance oil - a few drops should be enough. If the fragrance oils create a little tornado at the bottom of the glass and eventually turn into little flakes, you've got a polar fragrance oil. If the fragrance oil mixes in well, it's non-polar!

My two cents - put your stuff in opaque or frosted bottles and you won't know or care if it's cloudy!


Tara said...

When you describe how to test the polarity of your fragrance, you suggest adding a bit to cyclomethicone (which is non-polar, will not mix with water). The fragrance WILL mix cyclomethicone if it is NON-POLAR (non-polar mixes with non-polar) and will NOT mix with cyclomethicone if it is POLAR (meaning it SHOULD mix with water).
I think you have a typo there ;-)

Anjali said...

Hi Susan,

While using polysorbates, how to decide which Polysorbate to use for solubilizing, say for example fragrance oil..or any other oil in water-based systems ? or just go by trial and error??

Susan Barclay-Nichols said...

Hi Anjali. Click here to learn more about polysorbates. I hope this answers your questions! Have fun!

Paulo P. said...

Hi Susan, is it possible to have a clear shower gel/face wash surfactant based only, using glucosides (decyl, lauryl, coco)? Thank you :)