Yeh sure, I know basalt well, I only ask because most people are using it for cosmetic purposes. I have had similar experience to you though, I find it's interlaminar bond strength very poor - I was getting full fibres peeling off in strips rather than little bits like you have experienced. I always just put it down to the specific material that I was using, so it's interesting you have come to the same conclusion with a different supplier.

Was there a reason you were using basalt? 

So the theory is confirmed. The epoxy didn't seem to bond to the basalt fabric well enough and was being ripped off in places by the peel ply.

Made up a CF test piece using the same technique as the basalt before (degassing, resin break, keeping compressor on till gelling), with the same resin, and the results were as they should have been all along. After this I might just use CF and not bother with the basalt until I can find a compatible resin, or a better quality fabric. Thank's everyone for the input and assistance.

Update: The A side is completely flawless and there doesn't appear to be any aeration through the part, so gold star. BUT I'm still getting the surfacing on the peel ply side.
Looking at it under a magnifier it actually looks like the peel ply is ripping resin off the top of the part, exposing the reinforcement... I'm thinking this resin may not be entirely compatible with basalt fabric (or is just rubbish). I might switch back to CF after this. It's is super frustrating as this one should have worked properly!

Here is a closeup of the surface where it looks really obvious:

So I set up another infusion late yesterday to try all of the changes, and so far, the results look promising. As suspected the resin had a huge amount of moisture to boil off and doubled in volume for about 5 min under vac. This was was definitely worthwhile trying! The resin break also slowed the flow down through the whole process, and I cracked a tee piece on the vac line to reduce the vacuum towards the end to control any further boiling. Not sure if it was a combination of all or one thing specifically, but the resin flow through the bag was almost completely devoid of bubbles, and the reduction of vac towards the end seemed to remove the post draw boil that used to fill the catch pot.

Its only been about 12 hours and the temps overnight were in the low 20s so I haven't been able to de-mould just yet, but I have removed the bag to have a closer look... I'm excited for this afternoon!

Resin boiling off


Boil-free flow!


Debagged

I think it is also important to keep in mind that suction is not the driving force behind infusion (or even a syringe for that matter), it is pressure differential. When you draw resin through the laminate, it is being pushed in from the feed side through to the lower pressure outlet side, it isn't being sucked through. So in order for the pump to draw any air out in the case of a leak, that air has to be pushed through the entire laminate by the higher pressure ambient air to reach the low pressure front. It just isn't possible for the pump to draw out air post infusion if there is a continuous leak or even volatiles outgassing - at some point the air can't be pushed through the laminate anymore and it just remains in there as voids. Sure if you happened to develop a leak in a location where the air could go straight to the pump without having to go through the laminate (ie, the brake zone) then the pump will be able to maintain pressure, but the likelihood of that is so small it doesn't seem worth doing.

Both methods work fine.  Pump on and good resin break will work well, as will pump off on a sealed bag.  It can be hard to get a great resin break if the flanges aren't that big which means the part would end up a little dry as some resin would still suck out during the cure process until it gels.  This is avoided by clamping off and switching off the pump - however you need vacuum to hold to a very high level until the resin has gelled.

So both techniques can be made to work and some people get on with one versus the other better.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

MTI hose is awesome!  I agree with KLComposites and have had great results with Proset too.  

Here's some evidence from the Easy Composites documentation on infusion that Google found for me.  It contradicts the video (which I just realized is the source of this pump turning off bit) - it worked in the video but it is a bad idea in general.  Videos are otherwise excellent!

https://system.eu2.netsuite.com/core/media/media.nl?id=59028&c=3937524&h=ed6c113ff018e812d5f3&_xt=.pdf



Here's one more great infusion resource from Vacmobiles in NZ:

https://www.vacmobiles.com/resin_infusion.html


I'll be interested to see how your infusion goes when you try again.  Next time I'm unclicking the "Notify me of replies to this post" button!