usually vacuum pump produce oil fog when it is pumping air, when a good vacuum level is reached the fog produced is minimal. perhaps your vacuum bag was non perfectly sealed?

Hi Adelbolide,

Saff is exactly right - the VP435 vacuum pump (in common with most rotary vane vacuum pumps) will produce oil vapour when the pump is extracting air; if the bag is properly sealed then once all the air is extracted then the amount of oil vapour produced should be negligible (almost zero). Therefore, one of two things has happened;

1) The bag was not properly sealed in the first place (i.e. it always had a small leak) and therefore the pump has effectively been pulling air out of the bag all night.
2) The bag (or seal) punctured whilst in the oven. This most often happens if the bag is pulled tight near a taped seam - when the tape gets hot in the oven it softens slight and can move - if the bag is stretched tight near a seam like this then it can break the seal. Another way a previously properly sealed bag can puncture when it's put in the oven is during loading - sometimes the act of placing the part into the oven can puncture the bag, particularly if you have a metal shelf and a full 'envelope' vacuum bag surrounding the mould.

For this reason, we don't recommend running the pump unattended just in case a leak develops within the bag during the cure. *At the very least*, you would certainly want to be present whilst the part comes up to temperature and for as much of the cure as possible.

I hope this helps,

Best regards, Matt