I had some trouble soldering findings (PMC is porous and soaks up a lot of solder!).
I have had very minimal experience with PMC but the pieces I did
make I integrated into fabricated pieces. I found that if you flux and
put the solder chip on the finding and heat it to melt to the finding
then pickle all you need to do is flux the PMC piece and hold the
finding to it when you solder. The solder will stay attached to the
finding and jump to the PMC piece. I have had no problems with this
method at all. Another method (I have not tried yet) is inserting a
small sterling disk into the back of the PMC earring as the solder
point before firing the piece.
Amy O’Connell Jewelry