During the firing of porcelain, aluminous porcelain pieces, the flux bearing minerals transform in a glass phase. In parallel, new crystalline species are appearing. When the glass viscosity is high and the crystalline phase is important, the piece will not deform. When the glass phase presents a low viscosity and the crystalline phase is poor, then the piece tends to deform. The firing cycle and the formula can be adjusted. Some kaolin like Premium presents the adequate mineralogy and particle size distribution and reduces the risk of deformation.


  • New Zealand: Premium

Black spots

Black spots appearing on the glaze surface after firing can be due to many causes from raw materials to process. The staining effect of the contaminants can be diluted by a more intensive milling or removed by a fine sieving or installing magnets at different steps of the process. A high frequency cleaning of sieves and magnets reduces the risk of having black or colored spots. Some contaminants are not removable in a ceramic factory but can be removed by specific technologies during the kaolin processing for example.

Highly processed products

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