Guar gum is very sensitive to pH shifts and can lose its thickening effect quickly if the pH is out of its optimal range. Please make sure that the pH is well below 7 (a good range is 4-5.5). On the other hand, too high a pH level can also reduce viscosity. The viscosity is also dependent on time and rate of agitation, temperature (warm temperatures work better), and concentration. Guar gum can be combined with xanthan gum to increase viscosity. Also, please note that due to its high pH guar gum itself can make a formula alkaline thereby causing all kinds of problems including destabilizing emulsions and/or precipitating ingredients that are normally in solution.