By Laurie Price

This clock is the 19th century French clock belonging to Hatfield House in Hertfordshire introduced by Su Fullwood. It is a collaborative project taken on by the Clocks, Ceramics and Metalwork Conservation Departments at West Dean College. The role of the Metalwork Department has been to conserve the decorative ormolu (gilded bronze) elements of the case. I have been designated the position of team leader controlling the disassembly of components and the management of the conservation of each of the parts. This means carefully monitoring the whereabouts of just under one hundred pieces of ormolu amongst the hustle and bustle of five very eager metalwork students.

Cracks in ormolu

The disassembly was carried out over two days, precisely labeling each piece according to its exact position on the clock. The clock has three columns and with so many sections looking similar there were only so many times you could use the term "column base" for referencing. Some of the ormolu could not be removed, however, as attempts to do so might cause irreversible damage to the structure or the gilt surface of the metal. There are small cracks in places where increased pressure could encourage the metal to fracture further leading to more interventive treatment. This makes them particularly difficult to access and gives our reason for not removing them in fear of causing more harm. Whilst taking the clock case apart we also realised that two of the rods in the fluting of the black ionic columns were missing and needed replacing to maintain an aesthetic consistency. A rubber mould was made using one of the existing rods and wax replicas were made ready to be cast using the lost wax process. These will then be adjusted to match the others with a mark stamped into them to indicate that they are non-original additions.

Left: wax casts; right: new metal rods

Left: pin and wooden plug; right: hide glue around pin

Many of the sections have pins attached to the backs that are inserted into holes in the marble. This join is secured by wooden plugs in each of the holes, making a tension fitting between the pin and the marble. Over time the wooden, organic component has shrunk allowing the ormolu to become loose and more susceptible to damage. The base has several plaques, as well as one on the central column, where the fixing mechanism cannot be identified. This is because they are recessed into the stone and difficult to remove however, it is apparent on other pieces that both pins and hide glue were used. This is the result of FT-IR investigation into samples from three areas of the clock, all of which corresponded to the hide glue spectrum. It was then confirmed when a series of solvent tests were carried out with water being the only solution which the adhesive softened slightly. This meant that the hide glue could be removed very easily without interfering with the gilded surface but due to its stable condition it will be left as historical evidence.

Left: making an FT-IR sample; right: the FT-IR spectrum

The gilded surface has survived very well because of the unreactive nature of gold and therefore minimal cleaning is required. It is slightly worn in places where the copper alloy can be seen but this is typical for ormolu of this age. The dust and dirt accumulated on the surface will be gently cleaned, removing most of the blemishes so the gold has a more yellow gleam instead of the dull grey-yellow they are at the moment. It will be finished with a light coating of Renaissance Wax™ to protect the high points from wearing down to the copper alloy underneath.

Before cleaning

I anticipate many hours of ormolu cleaning over the next few weeks and hope to update the West Dean blog with news of our progress as the clock is nearer completion. In the meantime there will be numerous posts from other departments outlining their own conservation procedures for this impressive object.