Defect promoted by the glaze during application.

The effect shows a sort of outward migration of the glaze, that moves towards the edges of the tile and that turns (in those specific areas) into a thickening of the glaze itself: the aesthetic result is marked by a regular bulge that reminds of the old cathode ray tube TV screen. Thus the name.

The origin of the defect is usually the result of the very high surface tension of the water within the glaze suspension. The latter, in response to this tension, usually takes a spherical shape by moving towards the edges of the ceramic support, in order to decrease the surface energy.

Main actions to avoid the problem:

a) Increase the glaze’s drainage times by choosing proper chemical products;

b) Decrease the glaze’s surface tension by using proper wetting agents.