Sunday, December 19, 2010

Why we heat and hold our ingredients separately!

Someone recently wrote to me about heating and holding the oil and water phase together in the same container, and wondered why the emulsion didn't work (and it had worked in the past).

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!


papi said...

Hmm,that was really helpfull! Thanks for posting :*
I have a question, if we heat oils(like grapeseed) at 70 C won't it get rancid? And maybe we ruin some of it's properties too(like evening primrose oil) or the 70 C is the safe temperature? And last one, is there any chance if we heat glycerin to separate or become totally liquid??

Zenobiah said...

Another question: Do we need to hold both the water and the oils at 70 for 20 minutes? Or is it just the oils that have to be held that long?

Susan Barclay-Nichols said...

Hi papi and Zenobiah! You have to heat the oils to get your emulsification to happen, so we really don't have a choice in the matter. You can't add them at the end of the process in the cool down phase because they won't emulsify properly, so they have to be heated.

What properties are you worried about ruining with heating? Yes, it will speed up the rancidity of the oils slightly - for instance, you'll still get a year out of your olive oil - but it shouldn't destroy the wonderful fatty acids, polyphenols, phytosterols, and other lovely things you find in our oils.

We need to hold both phases at 70˚C (158˚F) for 20 minutes. As I mention in the post, having all the ingredients at the same temperature is vital to a good emulsion. Plus, we can get beasties in both the oil and water phases of the lotion, so it helps to kill anything that might be lurking about waiting to contaminate our lotions!

Papi, I don't understand the question about glycerin. If we heat glycerin, it will become easier to pour, but it returns to its slightly viscous state when it cools down. It won't separate because it doesn't contain any oils to separate. Can you clarify this for me?

Zenobiah said...

Thanks, that makes total sense to me now. Could you post some photos of how to do this in practice? Step by step for the noobs (like me)?

papi said...

Thanks for the responce :)
I was thinging that if olive oil goes minus a year, grapseed oil, which has self life about 6 months, how it goes? If we use a rancid oil we harm our skin by increasing free radicals, aren' t we?
You have completly covered me with glycerin :*

Susan Barclay-Nichols said...

Grapeseed oil has a shelf life of 3 to 6 months, and it's closer to the 3 month mark. Yes, we can mess up our skin and make a stinky mess with rancid oils, but we aren't heating the oils to the point where they will smoke or go rancid immediately.

Zenobiah: I'm not sure what pictures I could post about this topic 'cause it's a pretty boring thing to watch.

I put my water phase into one container, my oil phase into another container, then put both into my double boiler (my lovely Rival electric fondue pot) and let them sit until they reach 70˚C, which is when I begin timing the 20 minutes. I take them out at that point and pour the water phase into the oil phase (generally into a larger Pyrex jug) and mix for a bit. Then I let it sit until it reaches 45˚C to 50˚C and add my cool down phase (which I've generally measured out into a small container so I can clear off my workshop table). Mix. Wait. Package.

I'm happy to take pictures, but it sounds like it'd be pretty boring!

Kateryna Hryniw said...

Hi Susan,
I'm having trouble with the heat and hold phase, and at this point I'm not sure if I need a new thermometer, or perhaps a new heating technique. It seems that whenever I create a double broiler with a pot of water, and put my ingredients in a metal bowl over top my pot, my ingredients never seem to reach a temperature of 70 degrees as per my thermometer! Last time I used this technique to heat my ingredients for a good 40 minutes, and my temperature stayed steady at 55-60 degrees. So I applied my oil ingredients directly to the stove top on minimum heat for 20 minutes, and when I finally was able to attain the 70 degree heat as per my thermometer, my finishing product had a rancid oil smell, that overpowered my actual fragrance. I don't understand what I'm doing wrong, if the boiling point of water is 100, then ingredients in a bath of boiling water can surely reach temperatures of 70, no?

(I actually tried using this sugar scrub anyways cause I hate waste, but I had an eau-de-rancid-oil smell all over my arms, and it's definitely too unpleasant to keep!)

Susan Barclay-Nichols said...

Hi Kateryna. So you're putting your ingredients into a metal bowl on top of your pot of boiling water and they aren't heating up to 70˚C? Are you putting all the ingredients into the same container or do you have a container for the heated water phase and another for the heated oil phase?

I think the problem is that you have put the ingredients in a bowl over the pot, not into the pot. You want the container in which you've put the ingredients to be in the water. Have you tried this?

Check out thie post for more information on double boilers.

Nikos Giannakopoulos said...

Hello Susan once again.

I've read your basic conditioner recipes that calls only for the BTMS, preservative, EO and distilled water. There is no oil in this recipe so how do I add the BTMS flakes? Directly in the water phase after water had already been @ 70°C for 20min?

If you have already answer that somewhere in your blog, please show me the link.

Thank you in advance for your answer.


Sun Island said...

Hi, I have a question regarding heating and holding. Does it have to be on the stove or can it be heated in the oven (my oven will go as low as 140F)? I could then make sure the water and the oils are the same temperature.

Susan Barclay-Nichols said...

Hi Sun Island! I haven't tried it in the oven, so I can't speak to this method. If you try it, make sure you have a thermometer to measure your phases to ensure they are being held at that temperature.