PASTE-GEL FOR PRESERVATION AND RESTORATION OF CALCAREOUS MATRIX SURFACES AND PROCESS FOR PREPARING AND APPLYING THE SAME

摘要

The invention relates to a paste-gel, a process for preparing it and a process for applying the same for preservation and restoration of calcareous stone surfaces. According to the invention, the paste-gel consists of phyllosilicate clay mineral and hydroxyapatite. The preparation process, as claimed by the invention, consists in mixing 50...100 ml hydroxyapatite in aqueous suspension with 1...3 g of phyllosilicate clay mineral as fine powder, dried for 4 h at the temperature of 120°C, while vigorously stirring at the ambient temperature for 15 min, at 300 rpm, to result in a bright-white thick and stable paste-gel. The process of application comprises the mechanical dedusting of the calcareous stone with sulphatization patina, while ventilating, after which the paste-gel is applied by brushing, until forming a layer of 0.2...0.5 cm, it is left to dry for 15 min and then the exfoliated layer is removed, the so treated surface having a negligible sulphate concentration and unaffected chromatic properties.