Saturday, February 19, 2011

Learning to formulate: More fun with thickeners

I mentioned yesterday that increasing your thickening agents - like butters, fatty alcohols, and fatty acids - can make a lotion into a cream. Let's take a look at a 60% water lotion without thickeners, then consider what it would be like with different thickeners. Here's the recipe from which I will be working for this post...

39.5% water
20% aloe vera
3% glycerin

10% refined shea butter
10% soy bean oil
10% sesame oil
6% BTMS-50

0.5% liquid Germall Plus
1% fragrance oil (Clementine Cupcake)

Cetyl alcohol: If we remove 3% of the oils (any of the oils) and add 3% cetyl alcohol, this will thicken our lotion and offer some slip and glide to the product. Like all the other fatty alcohols and acids, it behaves as an extra emollient in the product. As a bonus, adding cetyl alcohol to a product with BTMS-50 as the emulsifier will boost the conditioning abilities, which could make for a more skin conditioning kind of product.

Cetyl esters: If we remove 3% of the oils and add 3% cetyl esters, this will thicken our lotion, but not as much as cetyl alcohol would. It will offer more slip and glide - thanks to the anti-tack properties - and you'll end up with a slightly thicker product than the original. (As a note, I think it's the cetyl esters that is morphing my vanilla based scents, so be careful in your fragrance choices.)

Cetearyl alcohol: If we remove 3% of the oils and add 3% cetearyl alcohol, we'll get a thicker, waxier feeling lotion than the original. It will feel more occlusive than a lotion made with cetyl alcohol or cetyl esters, and it will be thicker than either of these.

Stearic acid: If we remove 3% of the oils and add 3% stearic acid, we'll get a much thicker product than any of the previous ones with more drag and the possibility of the soaping effect. We'll also get a very tenacious cream, one that will offer a feeling of staying on the skin longer than those made with the fatty alcohols and esters.

What if I reduced the butter or replaced it with oils, what would these thickeners do? They'd thicken it! (Not meaning to sound sarcastic, but it's true!) If you have an all oil based lotion, adding 3% of one of these thickeners will increase the viscosity pretty dramatically. I'd say it's on par with adding 10% to 15%  butters to a product! And removing the thickeners will do the same thing. So if you have a body butter recipe you really love but want to make it into a lotion, remove the thickeners and see how you like it. You might still need to remove some of the butters - for thickness, as well for reducing the greasiness because 20% shea might feel great on your arms, but not on your hands - but you're on your way to creating a completely different lotion with a tiny change!

I remember when I switched thickeners for the first time. It was with a body butter recipe I found on the Dish. I didn't have any stearic acid, so I used cetyl alcohol. And the difference! It went from the consistency of whipped butter to being the consistency of Cool Whip! It felt much creamier and glidier, but it didn't feel like it stayed on as long as the version with stearic. I could really see the differences between the two products. Who'd have known that switching 3% of the recipe could make such a huge change in skin feel?

Join me tomorrow when we take a look at small changes making a big difference!


Anonymous said...

Great post!

Sam Austin said...

Are you saying that cetyl esters are made from soy? I've been using Carmex instead of other lip balms because I can not tolerate soy. It seems something in the Carmex has been giving me health problems and I need to know if it might be the cetyl esters. Can you help me?

Susan Barclay-Nichols said...

Hi Sam. I don't know. Anything that has palmitic acid (16 carbon fatty acid) in it is a candidate for becoming cetyl esters or cetyl alcohol. Considering that soy has very little palmitic acid, it's unlikely a manufacturer would use it as a starting point, but it is possible. (It's more likely they'd use coconut or palm oil as a starting point.) I'd suggest that you don't use Carmex or any other lip balm if you can't tolerate soy - there's no real way to know whence the cetyl esters, cetyl alcohol, and so on came! (Have you considered it might be the menthol in it? I hate that stuff on my lips!)

Anonymous said...

Hi Susan, thanks for your response. I now suspect the lanolin as I have found that it can be derived from vegetable sources. Carmex is definitely out.

Penny Sosebee said...

I formulated a cream with coffee butter & other goodies including Lanolin. I used steric Acid & Xanthum Gum.
I love the Mousse type feel of the cream but it does have a slight drag. If I swapped the Steric for Cetyl Alcohol, would this alleviate much of the drag?
I know there is a possibility that the Lanolin may cause some of the drag, but it is only 1% of the whole recipe.

Penny Sosebee

Anonymous said...

I'm new to lotion making and are obsessively trying to learn everything I can, not just about lotion but cosmetic chemistry in general. This blog is the best resource I have found, it has answered so many burning questions too obscure to find the answers to anywhere else. It has also really helped me decide what types of emulsifiers, thickeners and preservatives to order, something I really agonized over. Thanks so much!