The gelling and hardening reactions of tannin extracted from flower buds of Terminalia chebula with formaldehyde were analysed by parallel-plate rheometry techniques. In this study, a method to determine the rheological features of tannin-formaldehyde reactions both before and after the gel point was settled. The conversion from the liquid to solid state occurs at the gel point. Before the gel point, the zero shear viscosity can portray the behavior of the liquid resin. The value of this parameter rises as the polycondensation reaction proceeds, and at the gel point the weight average molecular mass turn into theoretically infinite.