Cleaning Nickel & Chrome Plated Keys
Many telegraph instruments, especially bugs, used brass parts that were nickel or chrome plated. Both of these types of plating can be cleaned using the method outlined below. Plating is nice because it protects brass from oxidation and discoloration. It does get dirty though, so it is important to clean it properly.
Chrome is the easiest to clean because it does not oxidize or patinate at all. (The metal underneath can oxidize however if the chrome plating is compromized by a deep scratch). It retains its shine for ages, especially if it is not exposed to the environment. Nickel does not patinate like brass but over time it can lose its shine and become more of a dull gray color if the key was stored in a damp environment. If this occurs, the shine cannot be restored without re-plating the instrument. As long as it has been properly cleaned, it will still look nice. Nickel plating is considered porous, so corrosive substances like finger oils or cat piss can leach through the plating and cause the underlying brass to oxidize, which in turn causes bluish-geen crystals to grow on the surface of the plating. This can be particularly bad on the keying levers of a bug, especially around the finger pieces. Sometimes an old nickel plated bug that was used by a professional telegrapher will be green with oxidation around the finger pieces due to corrosion caused by the operator's finger oils. An example of this can be seen on this old Double Lever Vibroplex bug. Another example is this early Vibroplex Blue Racer.
If you are unsure whether the instrument is nickel or chrome plated, an easy way to tell it to hold it next to something that you know is chrome plated, like a car wheel rim. Chrome plating has a bluish cast to it, while nickel plating has a slight yellowish cast. The difference is pretty clear when compared side-by-side as in this picture of 2 plated parts.
To clean the plating, get a bottle of Naval Jelly Rust Dissolver and some Q-tips or a small brush. After disassembling the instrument, dip a Q-tip in the Naval Jelly and proceed to paint each part. Clean each part one at a time. Leave the Naval Jelly on the part for between 1 to 5 minutes depending on how dirty it is. (Don't worry about damaging the part by leaving it on too long because Naval Jelly reacts with oxides of metal, not the metal itself.)
After treating the part, rinse it with water and scrub with a toothbrush. The crud will come right off ! Sometimes you will need to treat the part additional times if the oxidation was very bad like on the above example of the Double Lever Vibroplex. In situations like that, the original plating will likely already be completely gone in that area, replaced by nickel and brass oxides. So after the Naval Jelly treatment, you will be left with raw brass. Some might prefer to leave it like this, but if you want, you can re-plate that area of the instrument with a brush plating kit, as discussed in the section on Electroplating.