I'm still having a lot of doubts about preservatives...
How do you deal with (partial) hydrophobic preservative(s) (blends)?
For example, phenoxyethanol is added to the cooling down phase, due to its volatility, but won't it migrate to the oil phase instead of being active in the water and oil/water interphase?
* I want to try a few blends, but am not 100% sure in which phase to put them or to pre-mix with a water miscible solvent first:
Blend 1: phenoxyethanol (90%) + ethylhexylglycerin (10%);
Blend 2: 68% Benzylalcohol
0,1% BHT (to inhibit benzyl alcohol from oxidizing).
* I know non-ionic surfactants can deactivate some preservatives, like phenoxyethanol, parabens. But inspite of that, I see them combined all the time. Is this really something to worry about? Or is this only with polysorbates?
* And last but not least: packaging.
I read that low to medium density polyethylene is able to absorb parabens from a formulation and benzyl alcohol and phenoxyethanol are known to interact with polyethylene and polystyrene.
But aren't most packages made of polyethylene?
What are your thoughts on this?