More than twenty years ago, we posted some comments to rec.audio.pro about
cleaning condenser microphone diaphragms. I have decided to retire the local
copy of that article, because it seems to inspire too many to attempt things
that are unwise.

One thing left out of the original article is this: cleaning should only be
done if the microphone fails to work otherwise. The difference caused by a 
little extra weight may be audible, but not huge. Got that? No cleaning unless 
it *doesn't work.* And in no case should you use any source of heat near the 
microphone. Someone thought that what we wrote suggested putting steam on the 
microphone diaphragm. !!?! ...  the steam is to put a slight amount of pure 
water on your cleaning brush, not the diaphragm! No heat anywhere near 
diaphragm, OK? 

With all due respect to others in the field, if the conductive layer on
the diaphragm is so fragile that gentle cleaning with distilled water, alcohol
and cotton or a slightly damp fine brush damages it, you have no business 
cleaning it. That said, losing a small amount of metallization has little or
no effect -- the diaphragm will still behave as it did before, the
active area is just reduced a little. A real hazard, however, is that the 
capsule will become contaminated internally with whatever the cleaning medium 
carries with it, and will forever be noisy. This is particularly a problem with
older PVC diaphragms that have cracks. Unless you have a way to test for
ionic contamination of the surface and resulting leakage resistance of the
capsule, don't try it.

If any Josephson microphone appears to need cleaning, please send it back to
the factory in California. The cost is minimal and you can be sure of original 
performance when it's done.