To protect the shell from the high temperatures of the feed and combustion gases, a brick lining is used. The early rotary kiln patents of Ransome, Stokes and Hurry & Seaman simply specified firebrick (although Stokes went so far as to require best firebrick). The 3’6” diameter Ransome kiln had brickwork 6” thick. In the case of the Ransome and Stokes kilns, because real clinkering temperatures were never achieved, the quality of the bricks was a moot point. As rotary kilns began to be used successfully in the USA, the maintenance of the lining became a major preoccupation.