Hi, can someone please run through the degassing process, I’m using infusion resin, mix it up in a cup, place in degassing chamber, turn on the vacuum, bubbles start to rise as the vacuum builds, as I reach full vacuum it starts to froth over the top of the cup.
I guess I need to stop the pump before it gets this far? How long should it take? How will I know it’s ready? I feel dumb asking 
The resin will expand by as much as 6 - 10 times it’s original volume when it’s under full vacuum so you need to ensure you use a large enough container. If you cannot use a big enough container to allow for this expansion then you will need to apply the vacuum and keep an eye on it and close off the vacuum before the resin overflows, allow it to drop back a little and apply further vacuum, keep doing this until such time as you can apply full vacuum and leave it. The whole process can take anything upto to 10 to 15 minutes depending on how much air you have introduced to the resin during mixing. You will know when it’s ready because the resin will return to it’s original(or close to) volume and will have stopped(or close to) bubbling.
There is a good story on degassing in the august/sept 2011 edition of professional boatbuilder.
Are you degassing epoxy or polyester/vinylester?
Things that help is purging with air for the first 5 minutes. Stick a tube in the resin, and slowly introduce air while degassing. This does require some setup, however.
Also helping is a scotchbrite in the resin.
In any case, foam may develop rapidly, and cause a mess. Take a container large enough for the resin + foam. Play with the vent so the foam will not reach the top of the container (clear lids are great!) and you will find that there is a point where the foam collapses violently. After this the resin will settle, leave it for 1-2 minutes, and you are done.
For vinylester: H2O2-containing MEKP will cause a degree of foaming. Leave the vinylester for 5 minutes, then degass. This will get rid of most of the foam.
Easier is to get H202-free MEKP, but sometimes you just need the stuff in it.
Thanks guys, excellent advice!
how long does it take for degassing polyester resin? polyester resin tend to gel pretty fast so I was wondering how do you guys go about degassing polyester resin …
tanx
What I do, if I have too much in the cup and don’t want to waste another cup, is let it foam to the top, open and close the vent quickly till it drops down, and let it rise…and repeat until I see the larger bubbles, and it finally drops on it’s own. Takes 10min at times.