Heating and holding means heating the heated oil phase and heated water phase separately in two heat-resistant containers in indirect heat (like a double boiler) for 20 minutes at 70˚C or 158˚F. The 20 minutes starts when the ingredients reach the required temperature.
What do we heat and hold? We heat and hold the heated oil phase and heated water phases of lotions, and we heat and hold the water phases of things like shampoos, body washes, bubble baths, and cleansers. We don't need to heat and hold the oil phase of something like a lotion bar if we are making anhydrous or non-water containing products. But if we have a water phase, that product must be heated and held.
Weigh all your oil phase ingredients into a heat resistant container. Weigh all your water phase ingredients into a heat resistant container. Heat your double boiler up - I tend to boil up the water, then reduce the heat when I put my containers into the double boiler. Watch the temperature on your two containers. When they reach 70˚C or 158˚F, that's when the heating and holding starts. Get yourself a timer, set it for 20 minutes, and when the buzzer goes off, combine the two phases and mix!
The key to the heating and holding is the holding part. Heating things in a microwave enough to melt or boiling water is NOT enough to achieve the goals of heating and holding.
Why should I heat and hold? (Click here for the original post!)
1. Killing the nasties in our ingredients and/or water. When we heat the water and hold it, we will kill a lot of the gross little things that can get into our products.
2. Helping with emulsification. This one's a little more complicated.
Click here if you want to learn more about micelles before reading this post.
Click here if you want to see this post in full because it's really quite interesting!
I realize there are times that you have made a lotion without heating and holding for the full 20 minutes, and I realize there are some very knowledgeable people out there who swear by heating the ingredients up in a microwave, but having something work once or twice doesn't mean it works all the time.
Why do we need two separate containers? We're going to mix it all together eventually and/or I don't have enough space to heat two containers in my double boiler? (Click here for original post.)
Emulsification comes in three ways - heat emulsification, chemical emulsification, and mechanical emulsification. When you get an emulsion that works on day one but fails on day ten, it could be that you mixed it well enough to get a mechanical emulsion, but messed up on the chemical emulsification (not enough emulsifier or the wrong emulsifier) or the heat emulsification (not hot enough, phases not at the same temperature). It makes sense to heat all the ingredients in the same container - we ensure both phases are at the same temperature when we remove it from the heat to mix it - but it can make us think we have an emulsion when we don't. The phases need to be held separately so when they meet after the heat and hold, they have a chance to create an emulsion. If we have been holding them together, they could be doing the emulsification thing at much lower temperatures, which we know is unstable!
Here's a great quote from the legendary LabRat:
When you mix your emulsifiers, waxes, oils, water and other additives all together in one pot, you are making your emulsifier(s) work harder. That's not bad and it's not good but it's probably very inefficient.
What if I can't heat and hold?
As I mentioned in this post the other day, it's not expensive to visit your local thrift store and pick up an electric fondue pot or crock pot to help you heat and hold. Or you can create a double boiler on your stove top.
If you really can't heat and hold, then perhaps lotion making isn't for you. I know that must sound harsh, but I hope I've convinced you that it is essential to make safe, stable products. You can make anhydrous products (things that don't contain water) like lotion bars or scrubs because we don't generally heat and hold them, or you can make things like bath salts and bath bombs, but heating and holding is essential for things that contain water.
If you have any questions, please share them in the comments space for this post because this is a topic about which everyone seems to have questions! Join me tomorrow for more formulating fun!