xanthan gum before, but I thought I'd go a little more in depth in this post!
Xanthan gum is an anionic polymer derived from the bacterium Xanthomonas campestris, which can be found on cruciferous veggies like cabbage, cauliflower, and broccoli (all of my least favourites!). In the manufacturing of this ingredient, they actually use the bacteria in a fermentation process. It's permitted in food and cosmetic products and the typical usage is about 0.1% to 0.3%.
It dissolves in most acidic solutions (less than pH 7) and shows great stability in presence of most organic acids (like vinegar, lactic acid, AHA, and so on). It also shows good compatibility with many basic compounds, but something that is very alkaline like lye (pH around 12), you might see some precipitation of xanthan gum and salts. It is also unusually good with salts, but solubility is an issue. There is an incompatibility of xanthan gum and metal ions in solution with high pH, so addition of EDTA is a good idea if you're using some high pH ingredients like lye (although I can't see a good reason to make a really high pH product...)
decyl glucoside that don't contain a ton of salts with thicken nicely with it - but low concentrations of anionic and amphoteric surfactants (just about every other surfactant). It's not compatible with quaternary compounds, or you want to avoid using something like BTMS, honeyquat or polyquat 7, or Tinosan as your preservative. Salts can slow down the hydration of xanthan gum, but don't have much of an effect on it once it's hydrated, so don't worry about adding things like aloe vera that contain a ton of electrolytes.
You can use xanthan gum in your lotions in the oil phase of the lotions (which doesn't make sense to me as it is a water soluble ingredient, but that's what the data sheet suggests) and in your surfactant mixes in the heated water and surfactant phase to create a rich creamy lather. But remember, if you're making a shampoo, leave the honeyquat and polyquat 7 out!
Make sure you're using 0.1% to 0.3% because at lower levels in a lotion, it can actually enhance flocculation and creaming (otherwise known as an epic lotion fail)! So don't go below 0.1%. I've been experimenting with xanthan gum and Sucragel in lotions, and I've found 1.5% to 2% thickens a Sucragel lotion very nicely (and they're usually quite thin, no matter how much cetyl alcohol or butters you include in the mix).
Xanthan gum is pseudoplastic, so when it is subjected to stress it will thin out but will thicken up again when the stress is removed. And although it won't dissolve in alcohol, it is compatible with up to 60% alcohol, so it is an ideal thickener for making hand sanitizers. And like the other gelling agents we've seen so far, it will help decrease the freezing point of your products so they're easier to ship or store.
As a note, xanthan gum works really well in concert with other gums or thickeners. It works best with guar gum (80% guar gum to 20% xanthan gum) and with locust bean gum (50-50).
Join me tomorrow as I start experimenting in the workshop with these various thickeners in various products!