The micro-chemical features, the porosity and the thermal and mechanical properties of a commonly-used calcium sulphate-bonded investment has been studied as a function of the firing temperature and duration by means of the combined use of chemical/physical methods and electron microscopy. The results show a remarkable variation in the porosity, pore-size distribution, mechanical properties and thermal stability of the investment that are strictly related to the thermal expansion behavior and structural modification of the investment components. From a technological point of view, the results show that it is possible to tailor the final chemical/physical properties of a calcium sulphate-bonded investment by properly selecting the burnout cycle parameters.

Author: Dr. G.M. Ingo, Tilde de Caro, G. Gusmano, G. Montesperelli, C. Riccucci, P. Sbornicchia