I agree with Judymoody. Guar is tricky to work with and some people really don't like it and describe the texture as "snot". But to answer your question you can use it as a thickener in place of stearic.
Stearic is thick, stiff and will make your lotion hard to spread so I prefer cetyl in my lotions or better still behenyl. About 2% of either is v nice. Or you could up your butter % so you don't need a thickener. (Would be helpful to have your recipe in % so I can advise properly).
But if you do really want to try guar then I have copied and pasted below from my notes on how to use:-
Guar Gum - light emulsifier. prevents solid particles settling in a bottle, anti-freeze Use 0.2% to 0.3% for lotions. Method: sprinkle the guar gum over your room temperature water part of the 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.
Another method - 1 / Transfer the volume or quantity necessary to phase A (water) in a container. 2 / Transfer the required amount of phase B (guar gum) in a cup. 3 / Add all at once and once phase B into phase A and stir very vigorously with a mixer aerator or mini-whip without delay to avoid lumps. 4 / Continue to stir about 2 minutes, a homogeneous gel is formed
Note: It is water soluble, so it's not suitable for use in anhydrous products.
I've also read that guar is best mixed with another gum - 80% guar and 20% xanthan gum are supposed to work well together.
Do let us know how you get on.
