I had a conversation with Ed about this a couple of nights ago,
I did a razor handle in ebonite (green and black) and ended up buffing it to get the final finish.
Finally used it the other nite in the shower while shaving.
While shaving, I starting to look to see if the ceiling fan was ok, or if there was a problem.
Kinda went away when I put the razor down.
Picked up razor again, and the same burning rubber smell comes back
The hot water makes the lovely odor come out all over again.
As an ex-racer, the smell is still pleasant to me, but if you do not like that odor, then keep it out of heat
I wiped it dry, and put it away, today when I went to the cabinet again, and opened it, the odor from the ebonite was once again permeating the air.
Seems like the hot water drew some of the "oil" out of it into the air.