Andalusian Tilework (Mosaic of polygonal ceramic pieces).

Fátima Quesada has specialized in the reproduction of geometrical designs with the qualities of the ceramics (mechanical and aesthetic) we find in our historic heritage. She has retrieved this exquisite and laborious decorative ceramics technique developing a product which… reappears as both possible and viable in the 21st century. 

She studies each project and carries out a technique of “pre-assembly” which enables her to adapt and personalize the decorations with geometric mosaic (motives, formats, colours and types of pieces) depending on the requirements of the project (dimensions, two and three-dimensional aspects, style and functionality). 

She uses a specific clay for constructive purposes from suppliers who guarantee the homogeneity of it and mainly a good quality in terms of its cleanliness and composition. It is a low-temperature traditional kind of clay (temperature below 1100ºC) with a composition based mainly on calcareous components and very scarce in ferruginous ones to ensure her tiles have: 

Good mechanical resistance to bending (242 Kg/cm2).

Good adherence to mortars and glues (greater porosity than terracotta).

Low deformation and warping (during the ceramic process) due to its lower plasticity.

For the glazed tiles she uses the common metallic oxides present in medieval ceramics: kaolin and lead silicates for the composition of the glass and also iron, copper, cobalt, manganese and tin as the colouring oxides, to give the tiles their glazed finish. 

The process of elaboration is the following: 

Forming of sheets of clay, with the adequate thickness, laminating the clay by means of a clay extruder to which different nozzle outlets are added. These are specifically manufactured for the different pieces, which may be flat or with a certain angle. 

Manual cutting of the different shapes of the tiles. This process is carried out thanks to the laser-cut steel templates which Fátima designs and which a specialized company manufactures. The process of cutting is done one piece at a time, manually, using scrapers, blades and cutters -avoiding the use of more modern systems such as dies or moulds- because their cut is chiselled, as it was with old types of tiling. This way each tile remains strongly linked to the mortar, creating one only piece with the wall itself. 

The heat of the kilns is used to ensure the pieces are completely dry before their first firing or process to obtain the bisque tiles. 

For this last process, the pieces are placed within the kiln on top of a grid, leaving several pathways to ensure the flow of hot gases and so that all the fired elements are homogeneously fired. The firing of the “biscuit” is carried out at 1050ºC to guarantee the tiles have the maximum hardness within their genre (low-temperature ceramics). This firing takes between 7 and 8 hours. 

Combustion firing kilns are used in order to obtain the quality and tones of the glazed tiles which characterize the work of Alizares (since the oxides of the enamels are affected by the carbon of the combustion gasses). They use, as far as possible, digital pyrometry, insulating and modern refractory materials and firing programming.

Once all the pieces have gone through the process to obtain the bisque tiles, the pieces are glazed manually applying a superficial coat to them. No industrial mechanical means are valid for this part of the process due to the kind of shapes which are manufactured. To fire the pieces, these are placed in industrial saggars, which are reinvented to adapt them to the different small tiles. 

Their colours are glazed, following her own formulation in order to obtain the medieval Arab palette which is present in her range of colours and which she has achieved after successive calculations and trials. Moreover, she uses the minerals and original oxides which produce the old Arab colouring, avoiding the forgery that supplanting these materials would mean by using other more economic raw materials, currently used in modern manufactures. 

The firing of the glazing also takes around 7 hours and is carried out at 1000ºC. Its phases and the conditions of oxidation-reduction in the atmosphere of the kiln must be extremely under control and will be key in obtaining the very special quality of the colours of the tiles. 

Design and pre-assembly:

The first phase of work starts with the design, with the aim of elaborating a personalized project and because it will be possible to create with it the spreadsheets which will indicate the work to be carried out in the different areas of the workshop (what sort of pieces, the quantities, the colours, and how to prepare them for the order). 

All the models are commercialized pre-assembled generally in different “assembly modules” (groups of pieces adhered to a layer of film) which can be easily assembled with one another to cover a specific area without the need of cuts or their re-setting out on-site. They provide the plans and a “map” with the modules, numbered, indicating their position in the wall tiling.