Cloves are probably the strongest of all aromatic spices, containing up to 20 percent of an intense, sweetly pungent essential oil.
Originating, appropriately enough, in the Spice Islands, now part of Indonesia, they are the dried flower buds of the tropical evergreen tree Syzygium arornaticurn.
Dried clove buds have a stem and a head, a shape that gave them their name, clove, from the Latin clavus, “nail.” In the United States, they are most often seen protruding like spikes from the surfaces of hams. I hate it when I bite into one, don’t you?
Not surprisingly, cloves contain oil of cloves, the main chemical ingredient of which is eugenol, known familiarly to chemists by its nickname, -methoxy-4 (2-propenyl)phenol. You may at one time have had it applied to a tooth by your dentist as an analgesic and antiseptic.
Or, as I have done in Jakarta and on Bali, you may have smoked a few Indonesian clove-flavored cigarettes. These cigarettes, called kreteks, are filled with two parts tobacco and one part ground cloves. Indonesia’s passion for kreteks uses up approximately one-half of the world’s clove production.
Eugenol is a phenol, and phenols can have acidic and corrosive properties. In your case, the eugenol invaded, dissolved, and softened the grinder’s transparent plastic hood, which is probably made of polymethyl methacrylate, or Lucite. The aroma became permanently embedded therein.
I’m afraid you now own a dedicated clove grinder. Buy another coffee grinder for your less rapacious spices, and wash it out well after each use before you use it for coffee. Most other spices won’t permanently flavor the grinder.