Don't confuse guar gum with cationic guar gum - regular guar gum is non-ionic and does not offer any substantivity to your hair, and it's a fine white powder, not a yellowy powder. It will, however, behave as a good thickener for our products. It's water soluble and non-ionic, which means you can add it to more products than you could an anionic thickener like xanthan gum.
85% of guar gum is a water soluble polysaccharide called guaran. This is what gives it its thickening abilities. (That's the interesting molecule to the left!)
Guar gum is ideally used in products with a pH of 5 to 7, but it can handle higher and lower levels without degradation. We need to hydrate it before using it in our products, so it's suggested that you sprinkle the guar gum over your room temperature water phase, stick blend or mix well, then leave to sit for about 15 minutes or so or until it is well hydrated (you'll be able to tell because it creates a gel). Then you can add your other water phase ingredients like aloe vera, hydrosols, proteins, and so on and heat and hold as usual. The usage suggested ranges between 0.3% to 5%, so you'll have to do some playing to figure out the best usage for your product.
Guar gum offers more than thickening. It can behave as a light emulsifier as it prevents oil droplets from coalescing. It can behave as a stabilizer as it keeps solid particles from settling in a bottle. And it can behave as an anti-freeze by retarding ice crystal growth in our products (which is very useful when you're shipping things across the country and don't know where it might end up sitting for a while!).
Because guar gum is non-ionic, there are really no limits on where you can use it. You can use it in lotions, surfactant products, conditioners, and pretty much any product where you might want a little thickening. It is water soluble, so it's not suitable for use in anhydrous products.
Join me tomorrow for fun with hydroxypropyl methylcellulose!