Saturday, June 27, 2009

Better crafting through chemistry: Esters - thickeners (part 1)

Esters are well known to be efficient thickeners. You'll have encountered a few on your bath and body adventures - glycol stearate, glycol distearate (or EZ Pearl), Crothix - when making surfactant systems or looking for options for emulsifiers. (Crothix isn't an emulsifier, the others are!)

These are all PEG esters or polyethylene glycol based esters. The process of creating these esters is called ethyloxylation. Ethylene glycol or diethylene glycol and stearic acid are brought together with potassium hydroxide as a catalyst to create these PEG esters. Why mess with stearic acid? It's a perfectly wonderful ingredient! By ethyloxidating stearic acid (or other fatty acids, like vegetable oils) with ethylene glycol, you can create water soluble emollients, oils, waxes, fats, and other ingredients we couldn't normally use with surfactant systems or water based ingredients. (I'll be writing more about PEG oils tomorrow...)

Why would we want to include these ingredients in a body wash, for example? Because it's a great way to reduce the irritation of surfactants! All surfactants are inherently irritating and annoy your skin. You want to re-fat (that's their term, not mine) your skin with emollients after using a surfactant thingie like bubble bath or body wash. You could add some oils....but they aren't water soluble. They'll need an emulsifier and the oil and emulsifier are going to ruin the latheriness and bubbles. By adding one of these PEG based thickeners (or water soluble oil - tomorrow!), you can add water soluble emolliency without destroying your lather or foam!

Glycol distearate or EZ Pearl is a great thickener that also pearlizes your surfactant systems, or you can use it as a very low HLB (1) emulsifier in combination with something like Ceteareth-20 (15.2) to create your own emulsification system. Glycol stearate is also a great thickener that can be used for pearlizing, and it is a low HLB emulsifier (2.9) that can be used with Ceteareth-20. (For purposes of surfactant systems, these two products can be used interchangeably.)

I'm not going into emulsification with glycol distearate as I haven't done enough experimenting to feel comfortable sharing what I've learned so far, so let's take a look at modifying a body wash to include it! Oh, and feel free to use up to 3% in your shampoo as well. They are a great "oil free" way to moisturize!

(As an aside, when you see moisturizers or other products with "oil free" it usually means they have a PEG ingredient, stearic acid, cetyl alcohol, or other modified fatty acid that isn't truly an oil - with the glycerin backbone and three fatty acids attached!)

This body wash uses glycol distearate to act as an emollient, to pearlize the body wash so it's pretty, and to thicken your mixture.

The original body wash recipe can be found in this March 4th post.
37.5% water
15% Amphosol CG (coco betaine)
15% Amphosol AS-90 or SLeS
15% BSB or LSB
5% aloe vera
3% glycerin
3% Condition-eze 7
2% cromoist or other hydrolyzed protein
1.5% glycol stearate or glycol distearate (EZ Pearl) - you can go up to 3%, but try 1.5% first

2% panthenol
1% fragrance or essential oil
0.5% preservative
Colouring, if wanted

Heat the heated ingredients to 65C and mix together well until the EZ Pearl is incorporated. (I have found that heating the EZ Pearl in 1 container, the other ingredients in another until the EZ Pearl has melted, then incorporating the two containers works well). Make sure you are not seeing any little shards of glycol distearate in the mix.

When the mixture has cooled to 45C or lower, add the cool down ingredients.

You may need to include up to 1% Crothix if you are using fragrance oils that include vanilla or other surfactant thinning fragrances. Add this when the product has cooled completely and can sit for at least 24 hours (preferably longer).

A WARNING: These ingredients may not play well with your fragrance system. I made a beautiful batch of Black Raspberry Vanilla body wash that turned into very water surfactants with a layer of white glycol distearate at the bottom. It still worked, but it wasn't something I would want to give to someone as a gift as they would run away in horror. So I suggest making a small batch with the fragrance or essential oil of your choice, then making very sure it doesn't separate. Give it a few days. If it works, then you're good. Why does this happen? I have no freakin' idea! My current theories...
  • polar vs. non-polar fragrance oils
  • the role of vanilla or other fragrance oils that might thin out the surfactant mixture
  • too much glycol distearate, which messes with the foam too much and actually destroys the foaminess in bottle
(You know, I realized I haven't done any posts on stearic acid or cetyl alcohol...I guess I have some ideas for next week!)

Join me tomorrow for more ester-ific fun with Crothix!


Anonymous said...

I had similarly separated shower gel with 'PEG-120 jojoba esters' and oils: there was a white layer in the bottom of a bottle. I thought it was because of a wrong mixing process (I added some not very hot water at the end of a process)...

Crystal said...

What is the difference between Glycol stearate and Glycol distearate?

Heather said...

Hi Susan! I can't find glycol distearate anywhere but Voyageur in canada, and I'm in New Jersey! One of the sites I use here suggested I use glycol stearate IP instead, as it is supposedly nearly the same. What is your opinion on the substitution?

Thanks! Love you site and your hair care e-book!

drankid said...

Alright Swift. Ive gotten my butt kicked three times over this. I heated on its own and blended into water, Ive heated with the surfactants and blended in and heated all together and blended, and every time it not only wont thicken, but separates out into annoying little clumps. Help?

Susan Barclay-Nichols said...

Hi Drankid. Are you sure you have glycol distearate? Also, it really isn't the easiest ingredient to work with. What happens when you incorporate it with surfactants?

drankid said...

Positive. And it stays incorporated for a very short time, then hardens back up and separates out. I have a bottle with three very distinct layers after letting it sit; the top is perfectly clear, the middle is nice and pearly, and the bottom is white with all the chunks.

Nancy said...

I'm having issues getting it to incorporate into a shampoo as soon as I drop the temp it chucks up.

Susan Barclay-Nichols said...

Hi Nancy! What do you mean "chucks up"? Can you be more specific? How cold is the product becoming?

Kelli Spears said...

I have used Glycol Stearate for years in my shampoo, body wash and face wash and I haven't had any separation issues. I get mine from The Personal Formulator and they have Glycol Distearate also. I've never used that one, so maybe there's enough of a difference that it can cause problems in surfactant systems. The descriptions on each are a little different and the Distearate version says it's used in creams and lotions and as an opacifying and pearlizing agent in surfactant systems. I can tell you that when I use Glycol Stearate, I use it at 2% and I put it in the surfactant phase and I heat my surfactant phase very well, since I also use SCI and it takes a while to fully melt. Once my suractant phase is almost completely melted I heat and hold my water phase for 20 minutes. Oh, and I weigh my water phase before I heat. Then after holding for 20 minutes I weigh it again and add heated, distilled water to bring it back to the initial weight before heating. Then I add the water phase to the surfactant phase and mix very well. When it looks like it's mixed well I remove it from the heat and I stir it every 10 minutes or so til it cools. Comes out as thick as I like it and nice and pearly and I've never had it separate.
So for many of you who have had issues with the Distearate, you might give the Stearate version a shot and see if it works better. Hopefully it will.