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1. 1

   Keith:

   Posted 7 months ago by forum administrator

   The crackle glaze finish results when crazing lines form in a translucent glaze and are reflected by the ambient light penetrating the glaze layer. This is a decorative effect that is produced in a somewhat controlled manner by creating stress between the glaze and the tile bisque. This stress is achieved by formulating the glaze with a coefficient of expansion slightly different than that of the bisque. As the tile cools following the glaze firing stage, this mismatch in the coefficient of expansion forms a uniform network of random crackle features.

   Over time this same effect will be produced naturally on wall tile with a translucent glaze due to physical stress. As a building moves, the structure imposes stress on individual tiles and crazing lines form, albeit in a less uniform way. These crazing lines will continue to form throughout the life of the tiled surface, more in some areas and less in others. This can clearly be seen in vintage installations where translucent glazes were used as decorative liners.

   Solid, opaque white wall tiles will also form crazing lines gradually, and these features are vividly revealed when stained over the course of time. These natural effects of tile aging can also be seen in vintage installations and add to the character of these tiled surfaces.

   Solid color glazes are less likely to show crazing lines even when stained, but the glaze lacks the depth and luster of a classic translucent glaze. We do offer some glazes with this finish (Concorde Blue) but not within the Subway Ceramics collections as they are not historically authentic in the strictest sense.