Hi guys, was browsing the net looking for some information on this and that. Came across the composites central forum and read a post regarding the EC video on perfect resin infusion and the ensuing discussion. 

Hi Fabian,

Some people on the Composites Central thread may be missunderstanding what that video is about. In this particular video we're showing people how to make a part that's consmetically 'perfect' i.e. with no pin-holes or air bubbles and the only way to do that (in our experience, of which we have a lot) is to start with a perfectly sealed bag and then clamp of both lines (at which point you might as well switch the pump off because it's not doing anything).

If you leave the vacuum line open and the pump running you will bleed too much resin out of the laminate to have a perfect surface finish, you will get tiny pin holes at the intersection of the nodes and there's nothing you can do about it. That's fine if you're making structural parts for a plane, boat, car etc., in fact in those situations it's even preferable because you'll have a slightly lighter part but you won't have the same surface finish that you would get from the process shown in this video.

If you read our standard text guide about how resin infusion is done we even explain that the vacuum line is left open and the pump is left running, this is the traditional way to do resin infusion and there's nothing wrong with it, you just won't get the quality of surface finish that you will if you start with a sealed bag, clamp off and leave. So, choose the method that gets the results you want; for the very lightest possible parts leave the pump running, for the best surface finish clamp it off.

Different people will always have different opinions and it's great that they share them and contribute to widening knowledge generally. We put forward ways that work for us and have the highest chance of working for other people too. I hope that clears it up for you.

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

Hi Matt

I totally agree with you.

The single most important thing I have learned from you is the turning off of the vacuum pump. Thats a scarey deal if you don't have your confidence up.Who would ever think of closing off the lines in the first place! It wouldn't have occurred to me. The first time I did and got no pinholes I became a believer. (of course the resin viscosity was the other part of the puzzle I had to overcome. Heating the mold and the resin first).

Yes for compaction and strength you want the pump running, but for cosmetic parts it is a totally different story.

Thanks Again!

Fred