My brother has Maple Hardwood floors in his place, with a heavy coat
of clear poly-urathane to protect it. On this floor is a grand
piano. The Piano rests on three felt-bottomed coasters.
We recently moved the piano, and discovered that everywhere there was
coaster, the wood underneath was lighter than the surrounding wood.
(in a very clearly defined shapes). The floor itself is still
perfectly smooth and unmarred.
I was wondering if anyone had any ideas what caused the lightening (or
possibly the lack of darkening)? My first thought was it had
something to do with light, but the areas under the rugs which were
there the same amount of time, do not show the same lightening. Is
it possible that some chemical in the felt sept through the
polyurithane, and stained the wood???