I too had some Pierco frames that I removed that were black and difficult
to clean.  Being busy with other projects, I just stuck them in a nuc
that was sitting in a dark corner of the garage.  That was about 3 weeks ago.
Deciding that I now have the time to get working on them, I pulled them
out and had a pleasant surprise.  The wax moths have literally polished
several small sections to a gleaming white and are making serious inroads
to the rest of the frames.  If you have a few months to wait one could
utilize one of our worst enemies for this business of cleaning plastic
frames...
-
Cynthia