Tuesday, July 7, 2015

Heating & holding revisited...

I know I mentioned this only a short while ago in the Why did my lotion fail? Heating and holding post, but I'm getting so many questions about heating and holding this week, I thought it would be a good idea to remind you how important this process is to making emulsified products, including lotions and conditioners.

I know there are some well respected resources out there that say you don't have to do this, that heating your ingredients in the microwave until they are melted is enough, but it really isn't. Your ingredients can tolerate exposure to heat for a very long time - longer than we heat & hold, anyway - and they need this heat to make a lotion that will emulsify when combined and stay emulsified for ages to come.

The summary of heating and holding is this...We heat and hold our separate heated water phase and heated oil phase for 20 minutes at 70˚C/158˚F. Remove the containers from the heat, combine, then mix well with either a mixer or a stick blender. This process is what we do for every emulsified product from lotions to body butters to creams to conditioners and everything in between.

Why do we do this? To make the emulsion work better. If we heat and hold our ingredients at 70˚C for 20 minutes, we are assured that our emulsifier will be very oil soluble, which means it will create a water-in-oil emulsion that will eventually become an oil-in-water emulsion, which is very stable. We are assured our micelles will be a nice size, and we have eliminated many of the nasty contaminants that could ruin our lotion. In short, by heating and holding, we are ensuring we have a stable lotion that will remain emulsified and bug-free for a very long time!

When I teach classes at Voyageur Soap & Candle, we don't have a water bath to create a double boiler, so we can't heat and hold. We warm our water in the kettle and heat the oils in the microwaves. We use recipes I know will work well, but we still get failures. Why? Because we aren't heating and holding. You can make a lotion the microwave way, but you have a higher chance of failure than when you make it using the heat and hold method.

Why do some people forego the heat and hold? I really don't know. I've seen people say that our ingredients can't handle heat - they can! - and I've seen others say it takes too long, but neither of these are good reasons not to follow this process. It is the best practice for making emulsified products, and every professional recipe you see in a cosmetic chemistry textbook or from a large company that makes supplies has heated and held phases. It's standard practice to heat and hold because it makes for a better and more stable product every time.

I can't stress enough how important this process is to making a great lotion. I would say that half of the failed products that you write to me about are due to a failure to heat and hold. I'm not kidding about this. All those lovely ingredients, all that time, all that packaging could have been saved by heating and holding for 20 minutes. If you're not heating and holding yet and you've had a failed product, try it again with the heat and hold. If it's a well written recipe, that failure should be a success with this one small change.

Related posts:
Why we heat & hold our ingredients!
Why we heat & hold our ingredients separately
Weekend Wonderings: Heating & holding
Creating products: Heating & holding
What if you go over 70˚C when heating & holding?
How to heat & hold over a stove?
Does heating and holding damage our oils?

8 comments:

Bob Zonis said...

Susan,

I'd like to add a couple of comments:

1) I have successfully made water baths that hold ~70 degree temperatures nicely using an immersion heater, a digital thermometer, and a metal pan. (a small roasting pan works nicely) This heater is only $25:
http://www.omega.com/googlebase/product.html?pn=VPT-107-ADAP&gclid=CJra0qOdycYCFRQbgQodPa8OMg

2) I would strongly urge everyone to heat and hold both before AND after emulsification. There are significant stability benefits to be gained by holding at 70 degrees for 20 - 20 minutes after emulsification, then cooling. Stability can also be enhanced by cooling as fast as possible while stirring the batch constantly. The easiest way to do this is with an ice/water mixture in a cooling bath.

3) You can speed up your batch time by heating your ingredients/phases quickly, either in a microwave or in a double-boiler. If you have a constant-temperature bath held at 70 degrees, overheating a phase is not a problem - just stick them in the bath and wait for them to cool down to 70 degrees before emulsification.

Bob Zonis said...

I may not have made this as clear as I should have.

There are two good ways to heat your ingredients to make an emulsion. The first is to put all your phases in a ~70 degree bath, wait for them to reach 70 degrees, then hold for twenty minutes at 70 before emulsifying.

The second is to heat your phases separately and quickly until they reach 70 degrees, then put them in the water batch and hold for twenty minutes at 70 before emulsifying.

Using a heat source that's hotter than 70 degrees to hold your phases at 70 degrees for twenty minutes is tricky. It can be done, but your phases will need to be constantly monitored, and removed from the heat as soon as they've started to overheat (about 72 -75 degrees). Once they've cooled a little (about 65 - 68 degrees), you can return them to the heat source. You may need to repeat this cycle several times during the twenty minute hold time.

And one other thing - the water/ice bath for cooling to enhance stability gimmick doesn't scale well - once your batch size goes over 3Kg, it starts losing its effectiveness, and much past 5 kg, won't work at all. Since most professional labs use this gimmick to speed up batch times, this inability to scale up has embarrassed many cosmetic chemists whose basically unstable formulas were made just barely stable enough by the rapid cooling in the lab, but then failed stability when a larger, commercial-sized batch was made. But - if you never intend to make a batch larger than 2 or 3 kilos, this won't be a problem for you.

Bob Zonis
Senior Formulating Chemist, Beaumont Products, Inc.

Sandi MacDougall said...

I was doing another persons method of making lotion (I will not name names). I had pretty good luck, but it wasn't perfect. Now I heat and hold and my lotion turns out perfect every time. And it holds up to Missouri HEAT while I am at craft fairs, farmers markets, etc. Thank you, thank you. I am very proud of my lotion now!

Sandi
MacSuds Soap Co.

Megan Johnson said...

Susan:

I JUST googled "how to keep Pyrex jugs off the bottom of a double boiler?" about 20 minutes ago, and, naturally, Point of Interest was the third or fourth hit down. Thanks to you (and Amazon), I now have a round metal cooling rack on the way. Once I procure better thermometers, heating and holding will be a breeze. (Also bought some of those nifty tri-corner beakers from Lotioncrafter. Wheeeee!)

~ Megan

melian1 said...

i do my heat and hold in the oven. it is so easy and convenient. i melt the oil phase in the microwave in one container, heat the water phase in the microwave (to temp) in another container, then put them side by side into the oven and set my timer for 20 minutes. while they are heating and holding in the oven, i can prepare my workspace for the next phase of making the lotion. i clear away the ingredients that have already gone into one or the other containers, set out the ones still needed, etc. i don't have to watch and baby-sit the containers to be sure they are remaining at the proper temperature, or adjust it, etc. the oven keeps them at a constant temperature.

Nanette said...

Hi Bob,
I tried that link and it looked like a great immersion heater. But, turns out it is for a screw plug adapter for the immersion heater. You have to really look or head to checkout for that clarification.

Thanks so much for the comments on heat and hold. I've had success with EcoMulse mixing both phases together and heating. I will try that with other emulsifiers as well.

Stellarblew said...

melian1 try looking for thermometers at restaurant supply stores I picked up a dozen for under $30 and they have a clip to attach to the side of your container.

Stellarblew said...

Opps sorry that comment for Megan Johnson