Ceramic Tiles Manufacturing Process

Ceramic tiles are the result of a manufacturing process involving various phases, which change according to the different types of product, glazed or unglazed, to be produced.

Raw materials - Body
The bodies for the manufacturing of ceramic tiles are mixtures of different raw materials, including:

• Clay raw materials, which provide the necessary plasticity for subsequent forming of the tile
• Quartz materials, with a structural function necessary for limiting dimensional variations during drying and firing
• Feldspathic materials, whose function is to produce a liquid phase of suitable viscosity during firing

The body preparation consists of a series of grinding, mixing-homogenization, and water content regulation operations. At the end of this first phase, it is possible to obtain two different types of body: a powder with a 4-7% water content (suitable for shaping by pressing), or a paste with a 15-20% water content (suitable for shaping by extrusion).

Shaping and Drying
Most of the tiles produced today are molded by pressing. During this process, the body - in the form of a semi-dry powder - is compressed between two surfaces. This process gives the product the desired shape, as well as the right compactness and resistance.

Terracotta and Clinker tiles are shaped mainly by extrusion: the body of raw materials is formed into the shape of a continuous ribbon, and then cut as desired. Subsequently, the body water in the product is removed by means of rapid hot air dryers. Since this process is very delicate, it must be carefully controlled in order to prevent any damage.

Glazes and Glazing
Glazes are mixtures of different minerals and compounds ground in water, which are applied to the tile surface and fused onto it. During the subsequent cooling phase, the fused layer hardens to form a layer of glass, which gives particular aesthetic (brightness and color) and technical (impermeability and hardness) qualities to the tile surface

Firing and Sorting
The tile firing takes place in continuous roller kilns, which reach very high temperatures (from 900 °C to over 1250 °C). Inside the kiln the tiles are first heated to the maximum firing temperature and, after a defined period at this temperature, are gradually cooled. During firing the product undergoes chemical and physical reactions and transformations, which are required to obtain a mechanically resistant structure. The careful tile sorting is the concluding phase in the manufacturing process. There are three objectives to this phase: elimination of defective pieces; subdivision of tiles into first quality (first choice) and lower choice lots; grouping into homogeneous batches by shade and size.