Re: question about polyethylene/mineral oil cap construction

Ed, You said:
 "I was looking over the notes on building polyethylene capacitors 
in Chip's FAQ and I was puzzled by something. I believe Richard comments 
that after the minerla oil is added and one pumps the cap with a vacuum 
pump, the cap will "outgas" for quite some time. In fact, it seems that 
Richard says they will contine  to outgas to some degree for as long as he 
has has patience to pump. 

 What is outgassing? The oil, or the poly? Vacuum pump grade mineral 
oil will outgas at such a minimal rate that one should stop seeing bubbles 
after a short time. I wouldn't have guessed the poly unless gas is 
entrained durning manufacture..."

I believe most of the gas you will see will be trapped air slowly being
replaced by oil and rising to the top of the capacitor.  These capacitors are
rolled very tight (or should be) and trap a lot of air in them.  I have built
two of these.  I did not have a vacuum pump so I let them set for a week or
two after they were built before I applied any voltage to them.  Then I did
so slowly with low duty cycles.  I did finally get up to 12kv for a few
minutes on one of them and ruined it.  I believe the .0625 poly should be
used only at 9 or 10kv or less.

Ed Sonderman