Firing changes the shape of metal (warping)

25 september 2014 // Door webmaster //
During firing the metal has changed shape.
  • The metal has been hammered into shape, bent, sanded locally with great force or shaped in any other way without being annealed prior to firing, to alleviate stress in the metal.
  • No counter-enamel has been applied.
  • Long firing at too low a temperature. In general it is better to fire briefly at a high temperature than fire longer periods (> 4 min.) at low temperature.
  • Enamel and counter-enamel are applied with quite different coefficients of thermal expansion, or at quite different thickness, giving rise to stress between metal and enamel and warping of the piece.
  • Grossly uneven temperature in the kiln.
  • The piece was insufficiently supported in the kiln, so that large plaques sag. This can be remedied by flattening them down immediately after removing them from the kiln; prevent the plaque from giving way by providing enough support over the entire surface area during firing.
  • When firing with the open torch large temperature gradients may arise in the enamel piece. This may give rise to cracks in the enamel, or to enamel chipping off.


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