Conservator Charlotte talks to us today about cleaning a steel Persian Dhal to discover its intricately detailed decoration.
This steel Persian Dhal (shield) is one of a number of objects to go on loan to Bucks County Museum as part of their “Art of Islam” Exhibition.
At some point in its history this shield had been covered in shellac lacquer that had, over time, discoloured and trapped dirt against the surface. The lacquer had also been applied over tarnished metal and both these issues were obscuring the fine engravings and gilt layer across the surface of the shield.
We removed the old lacquer layer with solvents. This process had the added benefit of removing some of the corrosion product across the surface of the metal. We then applied museum-grade abrasion paste to remove the thicker areas of corrosion.
To protect the metal, we hot waxed the shield with microcrystalline wax. This technique involves carefully heating the metal and applying wax to the surface, which is then left to cool. Using a lint-free cloth we then rigorously buffed the metal to remove excess wax and create an even shine.
The cotton textile on the back of the shield was detaching from the metal and had to be secured back down. To do this, we aheared small tabs of Japanese tissue between the textile and the metal to act as an “anchor” and to allow for easier treatment reversibility.
We then inserted thermoplastic adhesive, applied as a “dry film”, between the Japanese tissue and the metal and then heat activated to bond the two materials together. A “wet” adhesive was then applied on top of the tissue, with the textile pressed down on to the adhesive and clamped in place, while the adhesive dried. This technique was repeated around the edge of the shield until the textile was secured in place.
The resulting clean and corrosion removal allows us to see more intricate detail and securing the textile on the back of the shield should hopefully prevent any further damage to this material.