Abstract: Thermal prestressing methods using unit and selective heating of tendons incorporated in a ceramic or cermet body to selectively elongate the tendon with respect to the body and soften the latter. Upon cooling an anchorage bond is formed between the body and the ends of the tendons, which bond develops a tension in the tendon and prestress in the body upon further cooling. Bodies are also prestressed by forming a bond between the tendon and the body and then heating the body in use so as to elongate the tendon relative to the body, the tendon having a greater coefficient of expansion than the material of the body.