Gel Rigidi di Agar per il Trattamento di Pulitura di Manufatti in Gesso. Use of Rigid Agar Gels For Cleaning Plaster Objects

Several of the authors of the present study have previously experimented the use of two polysaccharide polymers, Agarose and Agar, for gelling aqueous solutions, publishing the results in a recent Quaderno. These materials, which are able to form true "rigid gels" characterized by a particularly high degree of water retention, have proven appropriate for cleaning polychrome artworks. The main limit attributed to Agarose and Agar gels was their intrinsic stiffness, as stated in our previous publication; this in fact restricts their application only to practically flat surfaces. These conclusions stimulated the curiosity of several of the authors, in particular two restorers specialized in three-dimensional objects, terracottas, plaster objects, and marble sculpture. Might a different method for applying Agar be hypothesized, no longer using it in the form of a pre-prepared rigid gel, but rather during the cooling phase when the material is still in a semi-solid state, thus allowing it to be distributed over an irregular surface? The results of initial testing on plaster objects were very promising, to say the least: adequate cleaning appeared to have been achieved, while observation of the treated surface revealed no signs of erosion or other forms of interaction. We therefore decided to proceed with research, forming a work group which united the various persons who had already examined the theoretical aspects or performed practical applications of these materials, all of whom are represented here. Our studies have again achieved positive results, enabling us to "certify" this new system for Agar application.
The new methodology permits cleaning plaster objects in an efficient and innovative way, while remaining respectful of the porous nature of the substrates, which are potentially quite sensitive to treatment with water.