Lowering firing temperature and time in hard and soft paste porcelains

In this study, the effect of spodumene in tableware bodies was investigated under three main parts; namely, hard paste porcelain (high temperature), soft paste porcelain (low temperature) and low temperature-fast firing. In high temperature studies, K-feldspar-quartz, K-feldspar-alumina and Na-feldspar-quartz bodies were formulated. With the spodumene incorporation, it was found that liquid phase was formed 10 to 40 ? C lower than that of the standard, even at 0.5 % Li2O content. Additionally, 100 to 250 kg/cm2 increase in fired breaking strength values of K-feldspar bodies was observed. Total cost of the formulations was, however, still high due to almost 3.5 times high price of spodumene compared to K-feldspar in spite of reduced peak firing temperatures. From environmental point of view, though, the calculations showed that 15 ? C decrease in peak firing temperature of S2 composition corresponds to annual CO2 emission of forest with a size of 2.7 hectare. Amongst the developed formulations in low temperature studies, a suitable formulation (DD6) was chosen for industrial trials. As a result of the industrial trial, it was possible to produce a product, which is creamy cloured, translucent, zero water absorption and complies with TS 10850 Porcelain Tableware Standards after firing a 1180 ? C for a total firing of 5.5 hours. In low temperature-fast firing studies, it was shown that spodumene resulted in vitrification even at fast firing conditions of porcelain tile. The products with higher transluceny than hard porcelain was fired in a roller furnace at 1250 ? C for 88 minutes.