What is tarnish?
Tarnish appears as speckles of dark discoloration on the surface of solid precious metal and precious metal plating. Tarnish is not exclusive to musical instruments, it can be found anywhere that solid precious metal or plated surfaces exists.
What causes tarnish?
The very dark almost black looking tarnish is caused by exposing the silver to sulfur. In the presence of hydrogen sulfide in the atmosphere, silver forms a film of silver sulfide which is black in color. When silver sulfide forms on the surface of your flute, it darkens the silver.
There is some level of sulfur in air alone. Here are some situations that may create heightened levels of sulfur surrounding your instrument:
- The glue used in assembling the instrument case and its lining may have a high sulfur content.
- There may be high sulfur present in the perspiration and natural body oils in the musician’s skin.
- There is sulfur in the breath of the musician. This is particularly likely when having eaten high sulfur foods. High sulfur foods include: eggs, onions, garlic, cabbage, broccoli, mayonnaise, mustard and others.
- Vehicle exhaust, smoke stacks from factories (paper mills are rich sulfur producers) and fossil fuel power plants emit high levels of sulfur into the atmosphere.
Warning: Latex and rubber both contain sulfur. Do not put rubber bands around your flute! And don’t play with latex gloves on! Volcanoes put out major sulfur also. Stay away from volcanoes!
What about gold?
Gold that is used in flute making is usually alloyed with silver, copper and other good things. Therefore gold flutes will tarnish, but to a much smaller degree than silver.
There are a few ways to remove the areas of tarnish. One method is polishing off the sulfide layer. This is essentially what you do when using a “silver polishing cloth”. Professionals may use a buffing machine or polish by “hand ragging” with various compounds.
A very thin layer of silver is removed in this procedure, but don’t be alarmed. This polishing (also called buffing) is a process that is also used in the building of your flute. However, over-buffing certainly can compromise an instrument.
Another method uses a chemical reaction to convert the silver sulfide back into silver. This method does not remove silver. The next section describes how we use this process in our shop.
In our workshop
At J.L. Smith & Co., the way we clean flute bodies in the COA (clean, oil, and adjust) process (and the flute keys when we do an overhaul) involves attracting the sulfides to aluminum. Aluminum has a greater affinity for sulfur than silver does. The silver sulfides react with aluminum, and the sulfur atoms are transferred from the flute to an aluminum plate. This in turn forms aluminum sulfide on the plate. I like it when chemistry works for us.
After removing the sulfides, to restore the luster of the silver and to leave a thin protective coat, we hand rag the keys and body.