THE EFFECT OF MECHANICAL PRESSURE ON THE DRYING AND FIRING PROPERTIES OF TYPICAL CERAMIC BODIES*

Abstract

The drying and firing properties of hand‐molded and permeable‐pressed disks, 2 3/4 inches in diameter and 11/2 inches thick, were determined for sanitary ware, semivitreous ware, electrical porcelain, glass pot, sewer pipe, and chemical stoneware. Permeable pressing at 8280 lb./sq. in. eliminated drying shrinkage, reduced firing shrinkage by nearly one‐half, and the combined shrinkage by from one‐half to two‐thirds. The majority of the disks were dried and fired successfully, but some cracked on drying, probably from thermal shock, and some pressed disks were insufficiently oxidized or reduced due to their dense structure. Studies of pressing times showed great differences between bodies and, for any one body, that the pressing time depended roughly on the square of the initial thickness of the disk.