Double firing uses clays from owned quarries and chamotte, dry-ground, mixed and pressed with hydraulic presses. The firing of the support is performed in quick cycle with roller ovens at a temperature of about 1100°. After the glazing of the biscuit the glaze is fired in single layer roller ovens at about 1030°. The resulting facing materials have a tensile strength on average higher than 17N/mm2 according to UNI EN ISO 10545-4 and with water absorption higher than 10%, classified as BIII according to standard UNI EN 14411. These types of tiles have practically no shrinkage during firing, and this dimensional consistency results in a very easy to lay product and the production of large formats is completely ground.
Double firing tiles can be laid with adhesives and cement mortar. Select the most suitable adhesive by following the indications of the adhesive manufacturer. When using acrylic or vinyl resin adhesives and when using organic solvents based bicomponent adhesives do not wet before laying. When laying large format tiles use the double spreading laying technique and allow, for large surfaces, expansion joints that must not distance more than 4-5 linear metres from each other. See below for laying recommendations that ensure a good result: – when laying on concrete or plaster that is not dry yet, leave it to dry for at least a week per centimetre of thickness; – when laying using only cement mortar we recommend not exceeding 5 mm of thickness to avoid deformations of the tiles during drying; – when laying on brickwork never exceed 4-5 mm of thickness of adhesive per tile; – when laying on flexible supports (e.g. plasterboard, polymeric panels, etc.) that could generate movements of the tiles we recom-mend not exceeding 2-3 mm of thickness of adhesive per tile and using C2 or D1 class glue. Do not lay tiles without expansion joints or grouting otherwise the stresses due to expansion will be discharged directly on the tiles.