Promoted to lieutenant in the late 1930s to early 40s G.V. Corbett carried his officer uniform with him as he served. Evidence of rough handling can be seen on the box exterior through the loss of the paint and a hefty dent on one corner. However, the contents are in great shape. The box was used to transport Corbett’s bicorn, epaulettes and belt. They resemble today’s dress and parade uniform but will have been worn for normal duties aboard the ship. Today I’ll focus on the treatment the bicorn received, particularly the issue of tarnish removal from the metal threads.
The bicorn consists of three thread types:
Type 1. A thin silver and gold alloy spiralling and fixed to the bicorn using silk thread.
Type 2. A thinner alloy, wrapped around a yellow silk thread.
Type 3. A small circle alloy thread wrapped around a yellow silk thread.
When polishing metal it is important to remember that the process removes the top surface layer, and continued polishing can cause the loss of details. Maintaining a clean and polished appearance is an important aspect to military service, and something I felt was integral to the interpretation of the object. Polishing metal threads is notoriously difficult and has been approached from numerous angles of the years. Chemical and mechanical means both offer options, however they both have limitations.
Chemical options, such as silver dip and ammonia, can cause the swelling of the internal threads. There is also the risk of adverse chemical reactions and loss of dyes. Not to mention, the exposure of the conservator to toxic substances. Mechanical options cause physical damage, such as distortion of the threads. The use of abrasive cleaning particles can also cut the silk threads and cause the design to unravel.
Conservators always show caution when approaching a new challenge, however, many were reluctant to carry out any treatment on metal threads. The literature provided an overview of the options and systematically dismissed them. It left me particularly nervous to try chemical methods, so I decided to spot test calcium carbonate in deionised water on type 1 threads first. This proved to be unsuccessful as it caused the unsupported threads to distort and bend. The polishing affect was also slow to progress. I then moved onto chemical options. With the limitations of application, I wanted something fast acting that could be cleaned off easily. Silver dip fulfilled the criteria. To increase my control, I diluted to 50% with deionised water. I also degreased the threads with IMS before and after polishing.
The results were successful, and the threads now look cleaner and have regained a little shine. However, many limitations prevented a coherent polish. The layering of the threads stopped access to them all, and the risk of distortion to reach them prompted me to leave them be. It was also found that not all the tarnish could be removed easily. I decided not to extend the exposure in the hopes of removing it, the risks outweighed the potential rewards. Only type 1 was polished so as not to expose the silk threads and risk damage.
Corbett served in the Royal Navy in the 1930s to 50s, to recreate the high polished appearance of duty would not have matched the object’s age. However, calling back to those days is important in its interpretation and aesthetic qualities.