Conservation of a Tsuba

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By Sophie Harris

The first project for second-year metals conservation students is on ferrous metals. I received this Japanese tsuba encased in ferrous corrosion that has badly damaged the fine detail and had also consumed the gilding of this piece.

The dating of this object is difficult as designs and styles varied from maker to maker. The entire of the object is chased and engraved iron with damascening and amalgam gilded decorative highlights, with inclusions of gold, silver and copper alloy highlights.

Under the microscope you can see the potential for detail beneath the corrosion. A simple meticulous mechanical clean with a solvent and a scalpel blade underneath the microscope revealed the original detail of the piece.
During the cleaning process I noticed that there was a corrosion-coloured waxy layer in the low points of the detail.

Removal of this was difficult because solvents just moved the residue about, which made more unnecessary work and started to damage the gilding in the background, which had been completely encased in corrosion.

The removal of this was not necessary anyway; instead I felt as though the best thing to do was to stabilise what is there, as this keeps the integrity of the piece.

The iron was then stabilised with a chemical corrosion inhibitor of tannic acid 10% solution and 0.01% phosphoric acid. A minor pigmented protective coating of microcrystalline wax was then applied to prevent further corrosion.

To sit and reveal the beauty of this piece was a lovely start back to the term and ferrous metal objects. So I thought I would share it with all of you.