Also keep in mind that some of the gold is dragged out with the dross that is
removed on a daily basis when using a "dry" wave solder pot.  I have experience
with oil covered wave solder pots and they do indeed exhibit a build up of
gold, primariy because you are not forming dross and hence not removing some
contaminants.  We typically dumped an oil covered pot every 3 months either due
to gold or copper contamination levels.  When we changed wave solder machines
to a "dry" wave we found we could go years without dumping the solder pot even
though what we soldered had not changed.

Gordy Seppanen, Process Engineer
Military Avionics
Honeywell Inc.