The vast majority of 18th century brass face, tall case clocks have had the silvered dials polished by owners or domestic help, thinking that they could control the tarnish on the surface in the same manner they would polish the family silver. The problem was, in most cases, that they did not realize the tarnished silver they were looking at was only a very thin film of silvered surface. Once they started their “cleaning,” they very quickly polished through the silver coating, into the underlying brass surface. They were now faced with the perplexing dilemma of explaining a polished brass area in the middle of the tarnished silver. The only real solution, in their mind, was to continue to polish the silver surface until the entire area had a uniform, polished brass finish. Once they started down this road, there was no other alternative but to polish the brass for generations to come. This is why most 18th century tall case clocks have the appearance of brass on the surfaces that would have been originally silvered. The original silvered parts would have included the chapter ring, signature plate, and seconds dial, as well as the date wheel.
Another issue that we address at the same time is the corrosive aspect of the polishing compound that wicks under the chapter ring, spandrels, etc. During disassembly of the dial, we neutralize these corrosion issues so the damage of the polishing residue as it etches itself into the brass is halted.
We have developed a procedure to return the polished brass pieces back to their original appearance with a varying degree of patination representing how the silvered pieces would have aged properly over time.
The same silvering process that was used on 18th clocks was also used on compasses by the same makers, such as David and Benjamin Rittenhouse, Edward Duffield, John Heilig, and others. We have been successfully replicating the original silvering process using the same material that was used by the clock and instrument makers in the 18th century. We can now transfer that experience from the restoration of the silvered surveyor’s compass face to clock dials of the same period.