Abstract: Cylindrical castings (174), suited to thermal insulation applications at high temperatures, are formed by a centrifugal casting process. A mixture of carbon-containing fibers, such as isotropic pitch fibers, and a suitable aqueous binder, such as a sugar solution, is supplied to a rotating drum (12). The mixture is supplied via a feed pipe (18) concentrically aligned with a screen (66) of the drum. The fibers and binder collect on a filter cloth (102) supported by an inner surface of the screen. Excess binder flows through the filter cloth and passes through adjacent apertures (100) in the screen. When a cylindrical preform of sufficient thickness has built up, the drum is disassembled. The preform is dried, to drive off excess water, and heated to a temperature of about 900° C.-2000° C. to form the casting.