Cleaning and protection of historic objects – biotechnology and nanotechnology approach

Biocleaning procedure has been tested successfully on many materials and has proved to be more selective than mechanical and chemical cleaning techniques. Despite its success in treatment, biocleaning is not well-established method for the reduction of salt crystals. Therefore, the innovative approach combines biocleaning with the traditional (poultices) cleaning procedure. It is a new technology for salts reduction, starting from the design of clay poultices and joining their effects with targeted microorganisms. The chosen bacterial cultures increase the desalination capacity of the designed clay poultices, as a consequence of their metabolic activity, providing the mobilization of salts and salt reduction by the advection mechanism. Cleaned with this technology, architectural historic materials are properly prepared for long-term protection with photocatalytic coating based on TiO₂ and LDH suitable for fragile heritage materials. This protective material, designed under the FP7 HEROMAT project, has been already proved in laboratory and in-situ to be effective in maintaining aesthetic and functional properties of the mineral substrates and ensuring their long-term resistance to environmental conditions. This promising two-stage treatment presents a method which is both environmental friendly and cost/time effective for the reduction of nitrate salts and continuous self-cleaning protection of the surfaces of historic buildings.