Why does the color of the brass top change over time?
The tarnish that develops on brass is a mild form of corrosion, driven by oxygen in the air, oils from your skin, and any other chemicals that come into contact with the brass that are corrosive. The tarnish is not a problem in any way, and it actually protects the rest of the brass from corrosion. Part Two of this blog post is coming soon, where we will discuss ways to remove the tarnish back to bare metal if you want to restore the shine.
Why don’t you apply a clear coat to prevent tarnish?
There are several reasons: First, the use of a clear coat such as shellac or polyurethane initially sounds like a good idea. And it is a good idea for static brass parts that aren’t subject to wear. The top, on the other hand, is intended to be used. Regular use will inevitably chip or wear away the clear coat from portions of the top, but it will not do it consistently over the entire surface. These chips will be able to be felt and seen as a surface irregularity. Furthermore, once the clear coat is chipped the brass under it will tarnish normally and the top will have an uneven appearance, with bright brass and tarnished brass randomly distributed over the surface.
Bottom line, your brass top will take on a darker appearance over time, and that is ok! To minimize this and create the most uniform appearance, simply wipe it down occasionally with a soft, dry, cotton cloth.