Many factors have contributed to gradual deterioration of the structure: in their totality they are what constitutes its conservation history.
The original building technique has played an important role in the general deterioration process of the paintings; at the moment of the conservation intervention they presented a serious detachment from the wall support, affecting 80% of surface.
To understand the serious conservation condition of the frescoes, we can consider the “arriccio”. This preparatory layer has the purpose of leveling the walls out and to provide constant humidity in order to execute the painting on a new layer, according to the fresco technique. Originally it was formed by a 3-4 cm thick layer of clay mud, straw and stone dust.
Collapsing of the roof and partial loss of the plaster cover left this material exposed to erosion by wind and washing off by water; a material that is naturally fragile without a protective cover. Effects of environmental exposition have been crumbling of the arriccio layer, followed by accumulation of dust between the plaster and the wall structure. Parts of the decoration were found without any underlying layer, made heavier by accumulation of material in specific areas. Such an excess of weight on a structure that is not anymore soundly attached to its support caused collapsing of most of the decoration, in same cases seriously threatening its preservation.
The plaster, about 5 mm thick, is formed mainly by lime, vegetable fibers and stone dust, and it was applied in two layers. Indeed, with a macroscopic stratigraphic analysis it is possible to notice a very thin layer, called “intonachino”, without straw and with a smaller grain size in the filling. This layer has a compact and uniform surface, achieved through having properly crushed the mortar before applying the color.
A thin rope, pressed on the fresh plaster, was used to delimitate the composition space and to trace horizontal lines. Marks of the rope are still visible on the western wall, as well as tiny carvings regularly spaced almost to form a sort of frame for the composition of the Eros and Psyche scene.
The color was applied on the fresh plaster: it is well resistant to water, with a few exceptions due to the pigment’s fragility. Because of many losses in the painting film, it was possible to see the “sinopia”, the red color used both to trace the drawing and as a first shade for skin areas.
The painting execution was quick, as shown by the fast and simple brush strokes; on a uniform black background, volumes are defined by very dark outlines and overlapping color shades. The color palette is quite limited, involving natural earths and black. Only finishing in lime white and green areas of vegetal elements were realized on the plaster almost dry, with a “mezzo fresco”, half fresco, technique.