I recently made a mould out of glass fibre and resin and then finished it off with acrylic rattle can spray paint but after vacuuming my carbon fibre project it turned out to be a disaster.
I waxed the mould several times before applying the resin and laying the carbon fibre and then vacuum bagged it. It wasn't the easiest to release and it left an imprint on the moulds surface from the carbon fibre and ruined the product I pulled out.
Can someone tell me what I have done wrong and how I can rectify the problem? 

Don't use rattle can paints as a mould surface, they aren't tough enough. Even regular 2k paints aren't really tough enough to use as a mould surface, although you may get one or two pulls off them.

+x

 

Hanaldo - 6/28/2020 8:29:28 AM

Don't use rattle can paints as a mould surface, they aren't tough enough. Even regular 2k paints aren't really tough enough to use as a mould surface, although you may get one or two pulls off them.

Okay, how can I rectify the problem?

Well without seeing exactly what has happened it's a bit difficult to offer a solution, but ideally - remake the mould with a gelcoat.

Theoretically yes, but in reality no. You will never get that surface flat again, especially with gelcoats or resins. You'll lose your dimensions and it won't work. 

If its just the while chippy looking spots on the surface you might be able to patch but as Hanaldo says it won't ever be 100% - depends on what you need though.  No mold is perfect - the goal is to be the right amount of perfect to minimize the overall amount of work.  If you're going to make two parts - maybe patch it.  For 100 parts - make a new mold.  

I know rattle-can is easy and fast but there are much better choices.  Pattern-Coat or Duratec polyester primers are a much better alternative and can be sprayed from a small spray gun or one of those Preval sprayers.  It can be polished and will hold up way better.  Gelcoat is an option too but sanding it is more trouble.  The quick-and dirty fix might be to re-surface with one of these products and get a few parts - or re-make a master if your original plugs got busted in demolding.