Focus: ceramic glazes.

The problem is visible in the glaze under stirring along the glazing line and more specifically in the tanks connected to the application systems (spray cabin). If not properly managed, the foam – chemically defined as a stable system of surfactants in water – may cause defects the can compromise the quality of the final product: the micro bubbles on the tile’s surface can, in fact, persist even after firing.

PRECONDITIONS THAT MAY LEAD TO FOAMING PHENOMENA

1. Low viscosity of the glaze

2. High water amount

3. Presence of inorganic raw materials containing surfactants (and therefore potentially foaming)

4. Chemicals – such as fluidifying / wetting / binding agents – used in the grinding process

5. Chemicals – such as binding or wetting agents – added to the glaze along the glazing line

In general, the foam may occur in the presence of molecules that, under proper conditions, can perform or behave similarly to those of a classic surfactants (with polar head and hydrophobic tail)

Normally, when the phenomenon is not very aggressive, it is not recommended to use additional additives in order to not compromise the rheological features of the glaze. On the other side, when the problem seems to be out of control it is important to use specific defoamers. In extreme cases, a new formulation of the glaze may be required.