In order to investigate the effect of boron containing frits on anorthite formation temperature in kaolin-wollastonite mixture, four different frit compositions containing boron were prepared according to Seger formulas. One of these compositions also contained lead. Four different batches composed of 40 mass% kaolin, 40 mass% wollastonite and 20 mass% frit were prepared. The linear ditatometric (LD) curves of the batches were determined and subsequently the firing schedule (FS) curves were obtained from the LD curves. Cylindrical pellets prepared from each of the batches were fired in an especially designed furnace up to respectively 950, 975 1000 1025 1050 degreesC. The firing period including the cooling process was adjusted to 210 min. The variation of the bulk densities of the products as a function of temperature were examined. X-ray diffraction (XRD) patterns of the products were also determined and it was observed that the minimum anorthite formation temperature was 1000 degreesC. Since it was known that with batches not containing any frit, the minimum anorthite formation temperature was 1100 degreesC, it was understood that leaded or unleaded boron containing frits decreased the anorthite formation temperatures around 100 degreesC. (C) 2003 Elsevier Science Ltd. All rights reserved.