First infusion has porosity


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Roo2
Roo2
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Hello there,
I've just completed my first infused part. It's a shell for a home made metal detector coil. I'm generally happy with the result but would like to improve the surface finish on future parts.
The part is made with 2 layers of 200gsm fibreglass and a low viscosity epoxy that uses a very slow hardener. It took over 4 hours to start to gel in a warm environment. I'm using a pump that can get down to about -28" and  after I infused the resin it was turned off. No evidence of leaks where seen and the vacuum gauge needle didn't move for the entire cure duration.
If you look at the attached photo of the shell on the scales there are a few areas that appear to have porosity. Small holes between the fibre weave. Could that be caused by using hardener that is too slow and all the resin has been squeezed, drawn out of the very thin laminate? Or is it just evidence of tiny air leaks I couldn't see or measure?
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MarkMK
MarkMK
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If you're mould was porous, you'd definitely see evidence of air ingress during the infusion

As Hanaldo said, degassing is largely unnecessary to achieve perfect cosmetics. I too do infusions nearly every day and no longer bother using my degassing chamber as there has been no noticeable difference to parts even when starting the infusion very soon after mixing.

A lot of the trapped air will evacuate during the infusion process anyway and ensuring that enough resin has flowed to wet-out the stack is key to ensuring a perfect surface finish. Using resin breaks and making sure that every bit of your part has fully wet-out (even any excess peel ply near the exit) should ensure that your part comes out without voids, as appears to be the issue you've highlighted. Slowing things down is also helpful when using small-ish moulds



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