A temperature gradient is a physical quantity that describes in which direction and at what rate the temperature changes the most rapidly around a particular location.

In Ceramics, during the firing process, it plays a fundamental role on the proper evaporation of the water-amount of raw tiles. This means that when the gradient is constant and slow, the water within the support has the time to migrate and properly evaporate.

If the temperature increases improperly, that is irregularly or too rapidly, the ceramic body may explode.

What happens exactly?

The risk you run is water reaching a rather high temperature (say, well above 100°C) too quickly, causing what we might commonly call the "pressure cooker effect".

The water produces a violent PRESSURE that in turns causes a strong EXPANSION inside the ceramic body. The pressure, together with the expansion, is able to affect the mechanical features of the material producing a DEFORMATION and thaen the EXPLOSION of the support.