Sunday, December 19, 2010
Why we heat and hold our ingredients separately!
First things first, we can make a lot of things emulsify that won't stay emulsified. I remember making a lip balm with a tiny bit of glycerin. It seemed like it worked, but a week or so later, the glycerin started weeping out and made a horrible mess. If you whip a water soluble ingredient into an oil soluble creation - say something like aloe vera into a whipped butter - you will see emulsification as well, but it won't stay that way for very long.
You might recall that emulsification comes in three ways - heat emulsification, chemical emulsification, and mechanical emulsification. And here's the post on epic lotion fails!
When you get an emulsion that works well on day one but fails on day ten, it could be that you mixed it well enough to make it work (mechanical emulsification) but messed up on the chemical emulsification. Think about salad dressing. If we shake it enough, it turns into a lovely emulsion we can use to make any vegetable-y treat tasty. But leave it alone for a while and it separates into vinegar and oil again. This could be the reason that thing that shouldn't emulsify has emulsified. It may be stable for a short period of time, but it will eventually return to its state of un-emulsification!
We heat and hold our phases separately to 70˚C (about 158˚F) because we're trying to get to the phase inversion temperature, which ensures we get a lovely emulsion that will remain that way for quite some time. If we heat and hold our phases in the same container, we're getting emulsion way before the phase inversion temperature and it might create an unstable emulsification.
I know there are people out there who heat and hold both phases in the same container and it works for them and I know there are people who don't heat and hold but warm the ingredients in the microwave, but for the most part, this isn't the best way to create a lotion. To ensure you're getting all the long term emulsifying goodness, you'll want to heat and hold your oil and water phases in separate containers and add them together when they have both reached 70˚C!