question about polyethylene/mineral oil cap construction

Hi all,
	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...