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clay storage
The clay, extracted from the factory-owned quarries, undergoes a first selection as to possible impurities and contemporaneously, large stones are being eliminated. It is then stored in industrial sheds where it must be mixed several times in order to release gases contained in its natural status, harmful during the production process.
grinding
Clay and lithic granules of finest dimensions (part of which will act as “reinforcement” of the final product) are being ground to the desired size and stored in silos.
mixing
The next step in production foresees the mixing of the ground clay with water to a plastic compound. By means of a die plate it proceeds onto a conveyor belt which carries it to the bins of the moulding machine.
extrusion
The prepared clay then goes to a machine which pushes the clay towards the outlet after releasing the existing air present in the compound. A mouthpiece is fitted on the outlet of the moulding machine
to force the clay to conform to its shape. After a brief passage, the long block of clay, which is now in the desired shape, comes to a cutter which divides its into the desired length. The size of the defined piece is about 7 % larger with respect to the final size because the “raw” piece undergoes this percentage of shrinkage when dried an baked in the kiln.
drying
The extruded and cut pieces are automatically loaded on carts and are sent to drying chambers. In these chambers, which are heated to approximately 100°C by hot air regenerated from the kilns, the material slowly yields its moisture with the aid of fans continuously circulating the air. The moisture must be removed very slowly to avoid the piece from cracking which may occur if moisture is withdrawn rapidly. It is very important that the piece is completely dry before being processed to successive production steps.
squaring and brushing
The dried material proceeds to the squaring and brushing line. A roller line will carry the piece to the squaring machine which grinds the cutting edges to eliminate irregularities in size occurring during the drying process, and to measure edges in accordance to the ruling tolerances with respect to the drawn edges.
The piece is subsequently sent to the brushing machine which successively carries out the final smoothing process with a special abrasive paper and brushing, which is performed with a set of steel brushes that give the surface that classic rustic look.
At this stage, the piece finds a mechanism that overturns it to be processed identically on the opposite side.
If the piece is destinated to be “litos”, this second step is not performed and the surface is left as it was after extrusion and the drying process.
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firing
The material is now ready to be fired. It is loaded automatically onto carts that enter into the pre-heated kilns before proceeding to the baking kilns where the temperature is increased grdually to approximately 970 – 980°C.
The cooling process is considerably long to prevent the material from undergoing a sudden drop in temperature, which could cause damage to the final product (extraction). The total time required from pre-heating to cooling is over 70 hours for this so particular and unique clay.
Any variation in the size due to baking falls within the limits imposed by European regulations, with provide for a maximum tolerance of 1,3 % in dimension of the finished piece.
product selection and packing
If the material from the kilns is not to be split and boxed, the next step will be quality control, where an operator inspects every tile and defines the first or second choice (material with inferior quality is sent directly to scrapping). The first choice material will proceed on its course to a mechanism which staples the tiles, packs them in nylon sheets and sends it to the final packing on pallets.
If the material is to be boxed, the double tile will be split by a machine placed on the line and subsequently the quality control takes place. Last, the tiles will be automatically boxed in polyethylene boxes and sent to packing on pallets.
wetting
Among the numerous minerals that compose clay from the Impruneta area, there is one, calcium carbonate, that despite fine grinding and long baking at a temperature of approximately 1.000°C, remains active and tends to swell if exposed to air moisture. This would cause an infinite amount of small holes on the surface of the tile and thus would defeat all the work performed to fabricate this quality product.
As a consequence and in order to avoid the deterioration of the tiles, the finished and packed product must be immersed into water for several hours so that the calcium carbonate is “extinguished” definitively.
commercialization
The long itinerary is thus concluded and the material is now stored in our warehouse, ready to be shipped and valued all over the world. |
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