in Pursuit of the (not so) perfect solubilizer

If there is one single "No-go", "synthetic" ingredient that I am missing as a "natural cosmetics formulator" that is the polysorbate-20. I can not relate when my conventional formulator colleagues still sing the praise of the parabens and are sad and frustrated about all the increasing bans and the consumer dislike for them and secretly or even sometimes openly wish their comeback but I honestly miss the polysorbate-20 and its performance as an outstanding solubilizer.

What are solubilizers in the first place?

Solubilizers are in clear words match makers between oil and water. In definition and in chemistry they are similar to emulsifiers and both belong to the bigger group of surfactants but the solubilizers are usually water soluble and have a higher HLB. You might find some common ingredients in commercial solubilizer and emulsifier blends but you can not swap one with the other.

What we expect from a solubilizer?

1- working at a reasonably low concentration

2- having no impact on the color, scent and viscosity of the product

3- having a nice skin feel (no tackiness)

4- does not foam like a dog shampoo

5- ideally working for lots of essential oils, lipophilic vitamins and preservatives

I have to confess that I am still searching for a miraculous solubilizer that can check all of the above boxes.

For one: all solubilizers are surfactants and foaming is in their nature .

Then despite the poor old polysorbate-20 which was an all-rounder solubilizer when it comes to "naturally derived" solubilizers they are rather selective and work differently for different ingredients and work even differently with individual essential oils which all belong to the same group of ingredients.

The third annoying issue is that since you usually need a high ratio of the solubilizer:essential oil the skin feel is usually tacky and unpleasant.

This has brought us to the point that we have completely stopped using any solubilizer in our formulations and we rely on the scent of the hydrosols when we prepare toners and body splashes and completely avoid the essential oils in order to not use the solubilizer.

For a long while we worked with the symbio?solv clear and symbio?solv XC and they had a tolerable performance although the solubilizer:oil ratio was rather high. Then due to regulatory issues the supplier (Dr. Straetmans which was then swallowed by the Evonik) replaced both of these solubilizers with the symbio?solv clear + which although still one of the most effective solubilizers on the market, is a far cry from a perfect solubilizer.

I recently went for a search and we started testing a few (new to me) solubilizers.

The above photo is a test with lavender essential oil which is one of the more tricky oils when it comes to solubilization. Even with a 1:10 ratio which is quite high in terms of price, foam and skin feel, not all of our test candidates could do a good job.

Quite to my astonishment, all of the solubilizers we tested worked well for triethyl citrate in a 1:10 ratio

and again not all of them worked with a lipophilic preservative

We are now going to test a couple of other essential oils and then narrow down our choice and see if we can reduce the dosage of the solubilizer and then we'll compare the foam and skin feel (stay tuned for more results).