Preparation of clay mixture
The clay, taken from the quarry, is transported to the farm and placed in a special barnyard where it will undergo a maturing process of about a year during which, the organic substances still present can be transformed as a result of the oxygenation process favored by the succession of atmospheric agents.
After curing, it is taken out and brought to a large Dissolver or Turbo Dissolver where it will dissolve with water, which is responsible for washing the clay and dispersing the soluble salts. Following the dissolving, the liquid clay mixture is passed through a special Vibrating Sieve, which is designed to retain the impurities in the clay and the more granular particles.
Sieved it is conveyed to a holding pit where a Slow Agitator keeps it constantly in suspension, preventing it from settling to the bottom. From the holding tank, by means of a Membrane Pump it is conducted and compressed into a Filter Press consisting of a set of plates lined with filter cloths that allow the separation of water from clay and firming of the latter.
After a time of 6 to 8 hours, the clay is drawn off the discs and taken to the kneading and degassing stage, through special machines called kneading-degassing machines in which the clay is homogenized in the absence of air.
From the outlet of the degassing mixers, the clay is taken to the various processes that can be carried out either manually or with the help of molding machines by molding.
Manual forging: manual turning performed on the potter’s wheel, is used for the forging of pottery or round objects; in fact, the potter is able to give the clay the desired shape with just the help of his hands.
Forging by Pressing: For the production of objects of which a large number of pieces need to be reproduced quickly, the technique of forging by pressing is adopted, with the use of hydraulic presses on which a special mold is mounted.
Forging by casting: In this case, kaolinic clays of a whitish color are adopted, which are dissolved in water together with a fluidizing agent such as sodium silicate.The barbotine thus obtained is poured into special molds where it sits for about an hour after which the mold is emptied and then opened for the purpose of removing and finishing the object formed around the inner walls of the mold.
Molded objects, need a drying time for the ‘evaporation of the residual water contained in the clay. This process can occur naturally by exposing objects to air, or forced through the use of desiccators.
Once dried, the artifacts are placed in an Oven that can be electrically or gas powered. The first firing in about 12 hours, will bring the objects to a temperature of about 1,000 degrees centigrade, it is then followed by the subsequent gradual cooling, which occurs naturally by heat dissipation, or forcibly in about 24 to 48 hours, depending on the size of the objects and the mass that was placed in the firing.
After the first firing, objects can be subjected to glazing, which is done manually by immersing the object in an aqueous solution of glaze. The glaze consists of a composition of glass , opacifiers and fluxes finely ground in a special mill, in the ratio of composition given by the temperature to which it is to be subjected. Glazing can also be done by airbrush in a special booth. It is used to coat the surface of the object on which the decoration will then be applied.
In ceramic handicrafts, decoration is done by hand by skilled decorators, capable of expressing on the surface of the glaze, patterns applied with appropriate brushes so as to cover the object with meaningful decorations. For this purpose, ceramic colors consisting of mineral or metallic oxides mixed with fluxes are used, in the right amount related to the temperature of the second firing. The greater or lesser harmonization between the applied decoration, the use of color and the shape of the object will then constitute the elements of qualitative evaluation of the artifacts.
After decoration, the object is placed back in the kiln to undergo a second firing, which in 8 to 10 hours will bring the objects to a temperature of 920/950 degrees centigrade with an additional cooling time of about 18 to 24 hours. The result is an artifact of high value, known by the name of majolica, which has made Caltagirone one of the major centers of production.
Processing and Decoration of TILES
Above all, CEAR ceramics is synonymous with technical experience gained in-house across the entire production range.
Also for tiles and special pieces such as torelli, pencils, etc., the process starts from the production of the clays in-house and by means of a special die-cutting plant the various sizes 10×10 – 15×15 – 20×20 are produced while by extrusion from a special degassing mixer the various special pieces are produced. For this purpose, pure clay is used to produce compact tiles, and no commonly used additives such as pozzolanic sand are used since this type of manufactured products have revealed their limitations especially in mechanical resistance, abrasion due to treading, and glaze holding on the surface.
An initial firing cycle at 990° C brings the tiles to the maximum degree of vitrification of the mixture.
After the first firing, the tiles are properly glazed with suitable glazes and undergo decoration.
This stage which is the most important is characterized by the following process:
the decoration to be made stems first and foremost from a thorough research of styles related to our tradition and, essentially, to the Arab tradition from which it derives and whose survey was conducted not only in Sicily, but also in Spain and Portugal where the Arabs left an undisputed artistic legacy still visible.
Our tiles, in order to ensure maximum added value for the use of decoration that is made strictly by hand, are decorated by means of the “dusting” a traditional technique involving the execution of the design on a sheet of tracing paper, where small holes are produced to reproduce the path of the pattern in the same way as in the construction of patterns in embroidery. Then, by means of a pad consisting of charcoal powder, the decoration is transferred to the tile, and skilled decorators, on the remaining trace, will proceed to execute the decoration completely by hand, passing the various colors and outlines. In this way, the authenticity of a handmade decoration is guaranteed, but also the continuity and regularity of the same, in the various tiles that like a mosaic will compose beautiful designs.