Treatment of degraded limestones with ammonium phosphate and ammonium oxalate
represents the most interesting scientific prospect for the protection of
calcareous-based materials. The advantages of this treatment are derived from
the protective behavior of the natural oxalate patinas found on countless stone
materials exposed to the outside environment. The method developed by Professor
Matteini therefore envisages artificially inducing the formation of these
protective layers. The product is applied in a cellulose pulp compress. This
type of treatment is implemented internationally due to the following
advantages: great compatibility with calcium carbonate and great durability,
very low solubility to acid solutions, surface fixative effect, de-sulfating
Use of lasers for cleaning works of art
The use of lasers for cleaning works of art finds its motivation in the characteristics that distinguish this procedure from traditional cleaning:
– Minimal invasiveness: without the use of chemicals or abrasive materials, it is treated without any contact.
– High control: only on the degraded layer, operating with the utmost precision.
– Extreme selectivity: the alteration layer absorbs light, the substrate reflects it, so as to limit or stop the action of the laser.
– Very high precision: fiber optic lasers allow you to treat complex patterned surfaces.
In partnership with ESTIA Srl, we have successfully used this type of cleaning not only on stones but also on frescoes (Siena, Santa Maria della Scala, Sagrestia Vecchia)
Cleaning with atomized water
This method associates a good cleaning of stone surfaces with the elimination of soluble salts from the surfaces. The water exerts a chemical action by dissolving the gypsum and secondary calcite which are mostly the binders of the crust, which can thus be eliminated. The air conveyed under pressure to the nozzle reduces the size of the water particles making them smaller, so as to improve the penetration into the dirt and the consequent cleaning performance. This method, unlike cleaning with sprayed water, uses much less water to achieve the final cleaning effect.
Treatment with barium hydroxide for frescoes and fine plasters
This method was developed in Florence after the 1966 flood to solve the problem that plagued the frescoes attacked by calcium sulphate. Barium hydroxide reacts with carbon dioxide forming barium carbonate, a salt with a very low solubility in H2O, which gives a consolidating effect; it also reacts with calcium sulphate present in many frescoed plasters (efflorescence), to give barium sulphate, an extremely insoluble salt. The application of this product is generally done with a cellulose pulp compress and must be performed by operators with experience in the field.