HAAS + SOHN Treviso II, Equipment Sheet

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Cracks
in
the
glazing
layer
8
6. Cracks in the glazing layer
The ceramic oven tile is a brittle, porous and natural material which continuously works following changes of
temperature and humidity. Consequently some small cracks may occur in the glazing, so called hairline
cracks.
During slow cooling after firing, the glaze looks rather like a liquid than a solid substance. The ceramic oven
tile shrinks and the glaze adapts to its changes easily. From a certain temperature, however, the glaze starts
to behave as a solid substance with its own thermal expansion and thus some tension between the glaze and
the ceramic tile occurs. If – during cooling - the glaze shrinks more than the ceramic oven tile, the higher
stress values in the glaze may cause uncontrolled hair crack formation. All traditional and historically verified
glazes exhibit hairline cracks and many customers value them highly.
As for ceramic oven tiles a slight colour tint and hairline cracks in the glaze are natural. They do not
affect the quality and they do not represent any cause for complaints.