Thursday, February 10, 2011
Learning to formulate: The cool down phase
What do we put in the cool down phase? Pretty much anything that won't tolerate the heated and held phases of our water or oil, meaning anything that should be added at below 70˚C/158˚F. It doesn't matter if it's water or oil soluble - if it doesn't like heat, it goes into this phase. This generally includes extracts (hence the picture to the left), silicones, some cationic polymers (like honeyquat), most preservatives, Vitamin E, fragrance and essential oils, and fancy things like cosmeceuticals.
Most of our cool down phase ingredients call for 50˚C/140˚F or lower, so what should you do if you have something that calls for 60˚F/150˚F or 45˚C/122˚F? I like to consider my cool down phase to be 45˚C/122˚F, so I can add all the cool down ingredients together. You can add something that asks for 60˚C at 45˚C, but you don't want to do it the other way around. The key is not to add them at the higher heat and hold temperatures. (Click here for a post on when to include ingredients and what happens if you add things at higher temperatures.)
For instance, honeyquat wants to be added at 50˚C or lower, as does liquid Germall Plus. I can add those at 50˚C or 45˚C and see the same results. Don't go below 35˚C/95˚C as we'll start to see our ingredients become less soluble (the higher the heat, the greater the solubility of most of our ingredients, with a few exceptions). I generally use 45˚C/122˚F as the start of my cool down phase.
So there you have our three phases. Let's take a look at making a lotion base tomorrow.