Srša, Ivan:

Shouldn't we consider the experience of old Masters? (On the approach to historical painted and/or decorated façade plaster)

From the technological point of view, the experience we have had in Croatia with restoring painted and/or decorated historical plaster that had been continuously exposed to seasonal cycles and daily oscillations of the polluted environment in city centres, has been negative, to say the least. Once lime plaster was replaced by extended plaster, the deterioration of its original remnants on historical buildings was accelerated, and, in time, facsimile copies began to be made instead of their further protection. At first the copies were made on extended plaster, and recently mostly on industrial plaster with technologically harmonized colours. Disturbing data on the number of façades from which the original painted and/or decorated plaster has been completely chiselled off and replaced by extended plaster, or the pervasive industrial plaster, over the past forty years suggests that, unless this practice is stopped in Croatia, in the next two to three decades the façades of historical buildings could be stripped of all of their original painted plaster.

However, over the past forty years, even the experiments with a wide range of different materials for fresco restoration have not been harmless, regardless of whether these frescos were in the interior or on the building’s façade. From organic to synthetic and inorganic materials, from the former promising reversibility to the currently championed compatibility, frescos had to take all our trials and errors. Bearing in mind the fact that the interventions made thus far to protect historical plaster and paint have frequently failed to yield a quality solution that would preserve their original material structure, a possible solution might be sought among the remaining façades, that have still not been touched either by construction workers' or by restorers' hands, on them one can often discern several painted, and also plastered, layers.

With this in mind, wouldn't it be justified to wonder why the same procedure is not applied today? Why not protect the preserved historical plasters and painted layers – after some limited restoration research – with a new layer of lime plaster and coloured lime coats? Wouldn't it be better for the continued existence of historical plaster and painted layers on façades – instead of displaying them permanently – to plaster them over and paint them over using the same materials that were originally used, and to shelter them under a layer of "pre-sacrificed plaster and paint"? Placing them (either the original layer only, or several subsequent historical layers) under the new plaster and/or painted layer would prevent their degradation due to direct atmospheric exposure or inadequate industrial products used for their "protection". Such a substitute new layer, which can be periodically replaced, thus allowing monitoring of the historical layers’ condition, could be used for painting replicas of those historical painted elements that a critical interpretation would select for presentation.