“…This loop, which results from the breakdown in structure with shear, is characteristic of thixotropic substances (3,8,13). Since the structure also breaks down with time The existence of a hysteresis loop in the flow curves (rheograms) of thixotropic substances was noted by earlier workers (11,12) and a method of studying gels based on their hysteresis loops was proposed by Weltmann and Green (4)(5)(6)(7)(13)(14)(15). This method has been applied to many dispersions such as printing inks (5), pigment suspensions (15), cosmetics (10), and aqueous suspensions of attapulgite (3) and bentonite (2).…”