Straight out of Felder and Rousseau, "Elementary Principle of Chemical Process"
1atm = 33.9 ft H20 at 4 deg C.
Jake, I disagree. If the pressure (vacuum) gauge reads lower (less) than 0 psia then you are exerting more than 1 atm of pressure on the item in the bag. The benefit of the autoclave is that you can reach the high activation temperatures required for prepeg AND put it under pressure.
I think we're saying the same thing - you can't have a bag out in the open space (at atmospheric pressure), at full vacuum, and have more than one atmosphere on it. You can't achieve more vacuum than complete vacuum. You CAN increase the pressure outside the bag in order to increase the pressure inside the bag by using an autoclave to get better than atmospheric pressure.
