A rheological property of a condensed ceramic slurry used in the commercial production of high tension electrical insulators was discussed under the condition of lower pH. Two types of slurry were used, one was mainly composed of Kaolinitic clay, and the other was Sericitic clay. Discussions were based on the experimental results, i. e. the difference in the amount of adsorbed and desorbed ions on the particles surface, on the difference in the potential value, and on the microstructural difference observed through the SEM observation of those freeze-dried slurries. It was found that the difference in the rheological behavior between the two types of condensed ceramic slurry was brought about mainly by the difference in the aggreagation state of the clay particles due to the exposed mineral species, such as SiO2 or Al2O3, which preferentially appeared in the cleavage depending on the type of clay minerals used.
