Saturday, August 31, 2013
Weekend Wonderings: It's all about the polysorbates, baby!
WILL HEATING HELP AN EMULSION WITH POLYSORBATE 20?
In this post, Polysorbate 20 vs. polysorbate 80, Sam F asks, Do you think heating will aide an o/w emulsion when adding 0.3% eo's & 1.2% polysorbate 20 to water?
The short answer is yes, emulsions generally like heat. The long answer is...yes, but you have to put the things that can handle heat in a heated water phase and the things that can't handle heat into the cool down phase.
Related post: How do you know when to add an ingredient?
Most solutions - solutes dissolved in solvents or things dissolved or mixed into water - do better when heated, and emulsions are no exception. A good emulsion generally requires three things - a chemical emulsifier (like Polawax, e-wax, polysorbate 20, and so on), general agitation, and heat.
To create your recipe, ask yourself if all the ingredients are okay with being heated. Polysorbate 20 and water will be heated, whereas the essential oils and preservative probably shouldn't, depending upon the preservative. My recipe would look something like this....
HEATED WATER PHASE
water to make up 100%
COOL DOWN PHASE
0.5% liquid Germall plus
0.3% essential oils
1.2% polysorbate 20
Heat my water to 70˚C. No need to heat and hold it as I'm using distilled water, but I do want to get it up to temperature. Let it cool to 45˚C. (Or just heat it to 45˚C, but I generally don't remember to check the water, so I tend to boil it up, then let it cool.) In the meantime, mix the essential oils, polysorbate 20, and liquid Germall Plus (or water of choice) together and add when the water cools below 45˚C. Mix mix mix, and we're done!
In this post, Ronnie A asks, Is PEG-20 (Polysorbate 20) the best emulsifier to use for a oil and water hair mist? What percentage of Polysorbate 20 would i need to use if my formulation is approximately 20-25% oil and 70% water/Rosemary Floral Water and aloe vera juice.
Quick aside before we start: I've only seen polysorbate 20 referred to as PEG-20 in one place, and it's this Wikipedia site. (And as a note, there's a lot of information there that isn't necessarily accurate.) As I mention in this post, you might find them as "tween 20" or "tween 80", which means they're derived this way, or "span 20" or "span 80", which means they're esters of non-PEG-ylated sorbitan esterified with fatty acids. I recommend calling it polysorbate 20 because no one is going to know what you mean if you call it PEG-20.
Now to the question - Polysorbate 20 isn't a good choice for a hair care product. I have three reasons for saying this...
1. It won't emulsify 20 to 25% oil. Polysorbate 20 is meant to emulsify things like essential oils in small amounts, like 2% to 3%. Polysorbate 80 might be a better choice as it is intended for carrier oils, but not more than a few percent. For 20 to 25%, you need a proper emulsifier, like Polawax or Incroquat BTMS-50 or Ritamulse SCG and so on.
At 20% to 25% oils, you're on par with a full on lotion, so you need to use a good amount of a proper emulsifier.
2. Polysorbate 20 is a non-ionic emulsifier, meaning it has a neutral electrical charge. When you're making a hair care product, you want to use a cationic or positively charged emulsifier like Rita BTMS-225 or Incroquat BTMS-50.
Related post: Anionic, cationic, and non-ionic?
3. Polysorbate 20 is a sticky ingredient, and using more than 3% or so - depending upon your personal preference - can lead to serious stickiness in the hair.
I wouldn't use that much aloe vera in any product as it can get sticky. Try using 10% aloe vera, 10% floral water, and the rest water. Water isn't a filler - it has many uses, and you don't want tons of sticky things in your hair! And this isn't going to work as a mist. This will be a medium weight lotion, like this 70% water recipe. You will not be able to spray this product. You'll be able to pump it, though.
For a hair mist, consider using something like 1% to 5% oils, 1% to 3% BTMS-50 or Rita BTMS-225, 10% aloe vera, 10% hydrosol, 0.5% to 1.5% preservative.
Is this your first recipe? If so, please consider using a tried and true recipe that we know works - like this leave in conditioner - or find one in the hair care section of the blog?
AS A FINAL THOUGHT...
As a quick note, polysorbate 20 and polysorbate 80 are technically solubilizer not emulsifiers. Want to learn more? Click here for a post on solubilizers vs. emulsifiers.
Chemistry Thursday: Why oil and water don't mix!
Chemistry Friday: Why do we care about mixing and solubility?
Solubility of our powdered ingredients