When conservators in the mid-twentieth century attempted to clean the fourteenth-century frescoes of the Scrovegni Chapel, they applied a protective coating of animal glue. They believed this would stabilize the deteriorating pigments. However, this treatment backfired because the animal glue absorbed ambient moisture from the damp chapel air. As the glue swelled and contracted with changes in humidity, it exerted mechanical stress on the paint layer beneath it, ultimately causing the delicate tempera paint to flake off the plaster walls. Later, in the 1970s, restorers introduced a solvent wash to dissolve the glue, but the chemical reaction between the solvent and the copper-based blue pigments created a green patina. This unexpected discoloration altered the original color scheme of the sky panels. Consequently, modern conservation protocols now forbid the use of organic glues and organic solvents on plaster-based frescoes, opting instead for non-reactive synthetic polymers.
According to the passage, what was the direct cause of the tempera paint flaking off the plaster walls?
- AThe chemical reaction that occurred between the solvent wash and the copper-based blue pigments
- The mechanical stress produced as the animal glue swelled and contracted with variations in humidityCevap
- CThe ambient moisture directly dissolving the plaster support structure behind the paint
- DThe modern implementation of protocols requiring the use of non-reactive synthetic polymers