Originally Posted by nealtw
Yes but they are not left with a neg. pressure.
I never said they were in a neg. pressure. Naturally flat glass could not be in a pressure or a vacuum, or it would bow in or out.
It just like when a pull a vacuum on a air con. system to get the moisture and air out, then i put the gas in. Only difference is the air con. is all round pipe so i can pull it down to a 29" vacuum. Paul