Try envelope bagging to eliminate any chance of the mould leaking.

Ensure anywhere you play with bagging film is both clean and has blunted edges to reduce the chance of tiny holes.  You could make up a "blanket" by putting some breather fabric between two layers of normal bagging film, selotaped at the edges. You then have a softish and clean blanket to lay over your work table for bagging.

Try measuring the pressure drop over 8 hours.  It takes roughly 8-11 hours for the resin to gel in the mould using a slow hardener. Fast hardener takes 2-3 hours to gel.

If its a smallish part then use fast hardener and leak test it over say 3-4 hours and if the drop is negligible then you should be fine to infuse.

Hi Geoffrey,

I know it can be frustrating sometimes to get a perfectly sealed bag but I can assure you that after a bit of practice it does come a lot easier. You'll probably find that there is something that is causing your leaks and once you find what the problem is, you won't really suffer the same problem anymore. To give you an example is it possible that the leak is coming from somewhere other than the vacuum bag (one of the catch-pot connections or elesewhere); this should be easy enough to identify if you clamp-off the bag just before the bag; if you still drop pressure on the guage but the bag stays tight then the leak must be somewhere else. Another thing to watch would be if you have some sharp parts of the mould which are punturing the bag each time or if you're using 'tools' to ensure that the bag is down in the corners properly but actually these tools have sharp edges and are punturing the bag.

In answer to your various ideas about overcoming the problem, I'm afraid that I can't suggest that any of these will be the solution. Your idea of putting the bagged project in a sealed vacuum chamber would certainly be unsuccessful because you would effectively be removing the 1 bar of atmospheric pressure that is consolodating the fibre and making the infusion process work so the nett result of placing your vacuum infusion in a vacuum would be the same as trying an infusion with no vacuum at all. Other solutions such as double bagging are likely to increase the chances of bag bridging and shouldn't be necessary. Envelope bagging the whole mould would certainly be a good starting point so that you can eliminate the chance that the mould itself leaks or that the tape to flange is leaking.

I hope this helps. It might not feel like it now but you'll get to a point where you can reliably bag-up a project in 15-20mins and rarely suffer a leak.

Kind regards, Matt


Matt Statham
Easy Composites / Carbon Mods - Technical Sales