Nanoline, nanosilica, bacteria

 

The new technologies in the field of Restoration and Conservation of Cultural Heritage offer new tools for Restorers to resolve situations until now can not be addressed with traditional methods.

Of primary importance are the products  based on nanotechnology, such as nanolime and nanosilica, allowing the consolidation of surfaces.
The nanolime, hydrated lime particles suspended in alcohol of medium size in order of only 150 nm, allow to lime (product of natural origin) to penetrate and to reconsolidate both natural and artificial stones (plasters). (figures 1-3)
With them it is also possible to produce grouting mortar to seal micro-cracks. (figures 4-5)

The nanosilici, silicon dioxide particles in aqueous dispersion of microscopic size of less than 100 nm, penetrate into the surfaces painted creating new aggregation.
They are especially used for the decorated surfaces with a superficial disintegration. (figure 6)

Also biology offers new tools to facilitate the work of restorers in the important cleaning phases.
For cleaning of the black crusts sulphate origin, frequently very hard to remove (figura 7), are now being used sulphate-reducing bacteria, present in nature and harmless to humans, able to destroy the incrustations, preserving the integrity of the artwork of which they have overlapped.
For exemple, Micro4Art–sulfates is an innovative cleaning technology employing the sulfate-reducing bacteria (SRB) (figure 8a,b).

MECHANISM OF ACTION_Desulfovibrio vulgaris, thanks to its metabolism (figure 9), is able to dissociate gypsum into Ca2+ and SO42+ ions, and the SO42+ ions are then reduced by the bacteria, whereas the Ca2+ ions react with carbon dioxide to form new calcite (4) according the following reaction.

6CaSO4 + 4H2O + 6CO2 > 6CaCO3 + 4H2S + 2S + 11O2

In order to solve such specific sector problems it is necessary to have transversal competencies that enable the interaction of both the experimental scientific world, the one which produces and makes available to the market the variety of products for the resolution of various problems, with the sector that works on the construction sites for the preservation of the cultural heritage.

 

[di Vittorio Bresciani]