Studying frits with the heating microscope

Abstract

The heating microscope continues to be an extremely useful tool for studying the beahviour of materials undergoing heating cycles. In ceramics it is indispensable for studying frits and glazes. Nonetheless, manual analysis is extremely laborious and is often limited to recording the so-called “softening temperature” and in any case gives a very subjective measurement. Some years ago it was shown that a more complete analysis of the images provided by the microscope can yield more exhaustive information on the behaviour of the frit. However, these considerations have been almost completely neglected because manual processing is simply too complex. Now the use of computerised image analysis techniques allows all the data contained in the images provided by the heating microscope to be transformed rapidly into valuable and highly accurate information. One of the limitations of the old manual instruments was the need to use a very low heating gradient. Technological advances have brought firing cycles of the order of tens of minutes with heating gradients of more than 50°C per minute. New generation heating microscopes can reach heating rates of 80°C per minute and are therefore able to reproduce the thermal stresses that actually occur in industrial kilns. This article outlines some results that have been obtained with the new Misura heating microscope, which combines automatic image acquisition and processing with dedicated data processing software, together with a high heating speed kiln with automatic programmer.