Sunday, February 21, 2016

Why I don't heat my ingredients in a microwave!

I'm asked all the time why I heat and hold my lotions a double boiler instead of using a microwave to melt our ingredients. There are a few reasons.

I heat my ingredients for lotions in two separate containers: One for the heated water phase and one for the heated oil phase. I heat them to 70˚C for 20 minutes, then remove them and mix well. I heat and hold them because this is how it works best for me. It ensures all the ingredients are well melted - stearic acid melts at 69˚C, for instance - and it ensures that when I combine them, they'll emulsify well.

Remember that a good emulsion requires three things: heat, mixing, and chemistry. The chemistry comes from using a good, all-in-one emulsifier at the proper rate. The mixing comes from your stick blender or hand mixer after you've combined the two phases. The big thing is the heat. When you heat everything up to melted in a microwave, have you added enough heat to get it to emulsify?

Maybe, maybe not. When I teach classes, we don't have time for heat and hold. We heat the oil phase in the microwave until they're at 70˚C, use water that has previously boiled, and mix like silly. We use recipes I have made many many times in the last nine years, and almost once per class, we have a lotion fail with a well written, tested recipe. The only real difference is the heat.

But here's the other reason I don't use a microwave.

A seasoned participant in my class yesterday heated her oil phase in the microwave. After 45 seconds, the BTMS-50 and cetyl alcohol hadn't melted. After another 30 seconds, they were at 45˚C - too cold. After another 30 seconds, it was boiling and melted the plastic container and tablecloth. Thank goodness we were all so aware of the situation that no one was hurt! Boiling oil on your skin would have meant a hospital trip!

I know there are loads of you out there who are successfully using a microwave to make your products, and I don't want to dismiss those experiences, but these extreme temperature shifts simply don't happen with a double boiler, and I would hate to suggest something that could put you in peril!

On this blog, I'll always suggest you heat and hold your lotions in a double boiler because that's what works for me when I'm creating these recipes in my workshop. If you choose to do differently, the recipes might not work out the same way. And I would hate to see another picture like the one I just posted again!


Anonymous said...

My standard recipe is 2000 grams. I do not have double boiler containers that can accommodate that volume. So what I do is measure everything (yes, other water phase ingredients included) except the water, preservative and fragrance into one sanitized container, and then boil the water in an electric kettle. I pour the boiling water directly onto the other ingredients (I KNOW - heresy!). I then stir until everything is melted, which happens very quickly, then stick blend like crazy for 2 minutes. When the temperature drops to below 158 F degrees (between 158 and 140 is the manufacturers suggestion) I add my preservative and stick blend for an additional minute. Because of the volume, reaching this temperature can take 10 minutes or so. Once the temp is below 140, I add the fragrance, and again stick blend for one minute. I pour into containers while the lotion is still in a liquid state. I have NEVER had an emulsion fail, in the last 5 years of making this recipe regularly. I attribute this to a few things. I think the multiple blending at different temperatures AND using a stick blender are creating a stable emulsion. And I'm using the right amount of a quality emulsifier (ewax NF) and a well balanced water in oil formula (it's 73% water). My percentages don't match the ones you recommend, but its a lovely lotion and I'm very happy with it. And, despite the unconventional method, my process works.

Baby Kat said...

Very interesting. I normally use a double boiler for everything. I make cheese so I am used to using that method. Except when I need a couple of lip balms or I'm playing with small amounts like that, then I use the microwave.

Tonya S. said...

Hello! I have a question, I noticed that in this post plastic beakers were used for heating and holding (if I'm correct). Would you recommend glass pyrex for beginners who are learning to heat and hold or are the ones you used in the post okay? If so where can those plastic containers be found online? Thank you so much!

Susan Barclay-Nichols said...

Hi Tonya! Plastic beakers are fine for the double boiler, but they can float when you have a small amount of stuff in them, so I do prefer glass. You can get the plastic beakers at Lotioncrafter or Formulator Sample Shop. I'm sure there are other places, but that's where I get mine!