Once the clay is hydrated, the weakly positive charges are attracted to negatively charged platelet faces. The resulung three-dimensional structure builds rapidly at first, giving a quick increase in viscosity. As time passes, the remaining free platelets take a longer time to find an available site in the structure, and so viscosity increases at a progressively slower rate (18). This was observed in the F1 and F3 formulations (Figure la and b, respectively) which present a progressive increase of apparent viscosity in the days of analysis at room temperature (22 ø + ø2C). Apparent viscosity as a function of the days of analysis at different temperatures in storage conditions is illustrated in Figure 1. In both formulations, at 5.0 ø + 0.5øC and temperature cycles, apparent viscosity decreased in relation to room temperature. Moreover, these formulations presented a slight visual aspect modification with cluster formations. Lower temperatures possibly decrease the clay hydration speed, promoting particle agglomerates. In contrast, the F1 and F3 formulations at high temperature (45.0 ø + 0.5øC) presented a viscosity increase in re- lation to room temperature (as shown in Figure 1), which was perceived visually. This fact could be attributed to clay-accelerated hydration caused by high temperature, which accelerates the fitting of free platelets in the structure. Jefferson and Rogers (14) ob- served that thermally induced structural rearrangements, which are shown by slight swelling, occur when clay suspensions are stored at higher temperatures. Formulations F1 and F3 also presented notable drying due to water loss at high temperature, which could also explain the increase in apparent viscosity in this storage condition. These results indicate that the amount or kind of humectants in the formulations was not enough to retain water.