Prékopa Ágnes (szerk.): Ars Decorativa 31. (Budapest, 2017)
Kornélia HAJTÓ: Restoration Options for Architectural Ceramics
ing and the inspection of the trial surface by a restorer. Prior examination of the contamination deposit, use of the abrasive particles of hardness suited to ceramics, proper training of the technical staff and supervision by a restorer are all essential. Trials of sand blasting were carried out on unglazed pyrogranite on the faşades of the Museum of Applied Arts in 2012. (Fig. 2-3f A combination of chemical and mechanical cleaning is a recently developed latex-and- solvent agent called STONEHEALTH, a thick paste that is brushed onto the surface and forms a thin, flexible layer that may be peeled off 24 hours later. The material takes the surface contamination with it. Its exact composition is not given. On a trial cleaning on the faţade of the Museum of Applied Arts, we observed a very small cleaning effect. (Fig. 4)4 Steam cleaning involves a high-pressure jet of steam which detaches the dirt from the surface. (Fig. 5f In certain cases, this is an extremely effective technique. It is not suitable for some types of contamination, and trial cleaning is necessary. The great advantage of the procedure is that it does not damage the surface of the ceramic, is guaranteed chemical-free and is very efficient. How practical it is for cleaning the surfaces of large buildings is less certain. Nowadays, there are industrial steam cleaners available, and the question mostly comes down to planning. Care must be taken to prevent the dirty run-off water from causing discolouration elsewhere. Conservation and strengthening In restoration, conservation is a class of procedures applied to objects in a state of structural deterioration that puts them at high risk of ageing or complete destruction. 3. Steam cleaning test on the f agadé of the Museum of Applied Arts. Photo by Kornélia Hajtó The conserving agent is chosen to suit the material of the artwork to stabilize its structure and inhibit the processes of decay and decomposition. Since the 1990s, there has been increasing application of specially developed agents that strengthen building surfaces by impregnation. These are used to treat stone and ceramic elements that have started to crumble, or to fix rendering, stucco, wall painting and mosaics. The most commonly applied agents are silicic acid ethyl ester derivatives. Silicic acid ester is a compound involving quartz (silicon dioxide, Si02) and ethyl alcohol (C,H5OH). The chemical formula is: ch3-ch2-o o-ch2-ch3 \ / Si / \ ch3-ch,-o o-ch2-ch3 In the pores of an artwork impregnated with the agent, reaction with moisture in the air produces ethyl alcohol and silicon 99
