64 The challenges of cleaning an 18th-century polychrome high relief with sgraffito KEYWORDS: Cleaning; conservation; sgraffito; polychromy; water-in-oil emulsion. The cleaning of artworks is one of the procedures in conservation and restoration that needs most consideration by professionals, given its irreversibility, and the aesthetic changes it causes in the object. With this in mind, it is possible to better understand this question by looking at an intervention carried out on an 18th-century polychrome high relief wooden sculptured plaque (probably a fragment of a Baroque altarpiece), representing an angel with ‘Arma Christi’ (the instruments of Christ´s Passion), and decorated with sgraffito, a technique where parts of paint are scrapped to reveal gold leaf underneath. This object was in a poor state of conservation, especially the support (since the wood had been attacked by xylophagous insects, which caused volumetric losses and affected its integrity), but the original polychrome layer and the gilding were also very fragile, explaining why one of the main problems encountered was the proper cleaning of the angel's wings and tunic, as the use of a harsh solvent could result in the loss of those layers. This was truly an issue because in the preliminary cleaning tests - based on the method developed by Richard Wolbers (with different proportions of mineral spirits, acetone, and isopropyl alcohol) - all the options were proven to be too aggressive, resulting in the removal of the gilding. As such, it was necessary to find a solvent suitable for this function. The choice fell on a water-in-oil emulsion, composed of a mineral spirit, water, and a surfactant. This emulsion was ideal, as it provided the perfect balance between cleaning the accumulated dirt/debris and ensuring the gilding and polychromy stability. xavier.pedrosa[at]sapo.pt
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