The dehydration reaction kinetics of tincal and-borax decahydrate was investigated by thermogravimetry (TG) and differential thermal analysis (DTA). Various methods were used to analyze the TG and DTA data for determination of reaction kinetics. The activation energy, frequency factor, and order of reaction were calculated for both materials. The results obtained from different methods were generally in good agreement. The results of tincal and borax were also compatible.