Saturday, April 24, 2010

Surfactants: Building viscosity - increasing micelle size

The second way to increase the viscosity of our surfactant-y creations is to increase the size of the micelles. (Please click here for a refresher on micelles!) We learned in the post about increasing mildness that increasing micelle size can reduce irritation, so you're not only building viscosity, you're decreasing irritation! (I love two-for-one processes!)

We can do this by using salt, by adding surfactants like the betaines, or by adding fatty materials, like Crothix, PEG-150 distearate, EZ Pearl (glycol distearate), or other thickening esters. Because surfactants have those hydrophilic heads and lipophilic tails, the fatty materials will become trapped in the middle of the micelles, causing them to swell. This creates viscosity in our products.

If you are using these fatty materials, be warned that some will pearlize or cloud your product. Crothix will create a clear system, but EZ Pearl is definitely something that will make it very opaque, which can be very pretty! (This was thickened with EZ Pearl - you can't see the pearly look, but it is lovely.)

These products thicken very well, but may not play well with your fragrances. Keep a list of those fragrances that thin or thicken your mixture so you can compensate for that change. (For instance, I find the black amber lavender and cream cheese icing fragrance oils from Brambleberry thicken my products like silly - I love it - whereas the jewelled citrus thins it like crazy!) I like to use liquid Crothix to thicken so I have more control over the product - I make something like a bubble bath, add everything but the Crothix, and wait until the next morning when it becomes clear. I can add the Crothix then - 0.5% at a time - to see how it thickens up.

Join me tomorrow for fun increasing our viscosity by making gels!


Cindy said...

Thanks for sharing Susan, I've been looking high and low for more info on surfactants!

Robert said...

I have a medical background, a Ph.D. in biochemistry, and a US pat. (now expired -- 5,336,446) on a low urogenital-irritancy bath foam, but I'm learning a good deal here. Thanks for the public service.

Abbie said...

Hello there, I'm new here and I just wanted to say how amazing you are and how happy I am to have found this. I've been having a lot of problems making my shampoo and now I have a bunch more things to try.. thank you so much. :)

dizzi said...

arrgh, I can't find neither EZ pearl (glycol distearate) nor Crothix liquid in the UK and my shampoo is too thin.

I've experimented with salt but was not too happy, and guar gum was too rubbery. I can go back and try to tweak salt and/or gum, but ideally i'd just like to use one of those alternative thickeners... anyone knows where i can buy them in the UK?

7slaper said...

THe Soapkitchen sells pearliser; it isn't straight glycol distearate, but it thickens shampoo etc.
Gracefruit sells GFsoft 767 INCI-name: PEG-6-Caprylic/Capric Glyceride. You should mix it with solid Crothix to make your own liquid Crothix.
If you can't find solid Crothix in the UK, you might try Youwish dot nl; they are the exclusive distributors for Brambleberry in the Netherlands. It is not yet a regular item, but if you ask them they will order it for you at BB.
(I'm Dutch b.t.w.) :)