In ceramics, "slurry" refers to the mixture (or SUSPENSION) of water, clays, and raw materials that form the base of the ceramic body.

This mixture undergoes several stages and treatments before being compacted under presses, which shape the unfired tile, ready for the subsequent steps along the glazing line and prior to entering the kilns.

Although complex, these stages can be summarized as follows:

1. MILLING: the clays, sands, feldspars, and inorganic raw materials are ground in mills through a wet process, which essentially involves the addition of water—mainly groundwater and process/recycled water. The latter is largely recovered from the glazing line and from the post-firing stages, such as grinding and polishing. The raw materials mixed with water form the slurry, also known as slip.

2. SIEVING: once milled, the slip exits the mills and is sieved to achieve uniformity by retaining any oversized or anomalous particles.

3. STORAGE: after sieving, the slip is stored for varying periods in storage tanks, where it is kept under constant agitation to prevent possible sedimentation or gelation phenomena.

4. SPRAY DRYING: following storage, the slip undergoes spray drying via spray dryers (also called atomizers).

Inside the spray dryer, the slip is nebulized at very high temperatures, which cause the water to evaporate rapidly and forcefully. This evaporation transforms the individual droplets of slip into tiny hollow spheres, collectively forming the spray-dried powder, ready for pressing/forming.

5. PRESSING: at this point, the spray-dried powder is ready to be pressed/compacted to form the unfired tile, which at this stage still retains about 5% to 7% residual moisture.