Quick question:
I had an idea to use a PVA glue coating over a pre cast resin part, then casting that part back in more resin. Once it was done I would remove the PVA in water theoretically giving me a moving part inside a cast resin object.
However, does anybody know if the PVA would react/dissolve in the new resin going over the top?
Cheers 
Should be OK , I have left a tin of slip wax in the metal box in the workshop if you want to try that
ill give PVA a go first as i already have some of that. If that fails then ill give your wax a go
Thanks!
Couldn’t you do that with any sort of mold release over your part ? Vaseline you can smooth with a heat gun for instance. Then just wash it off with soapy water.
i was thinking that, but if i used PVA it would have a tolerance of 0.5mm or something. If i used a mould release spray it would be much less meaning it might not move smoothly / much at all. The parts ill be using to make the mould will be 3d printed, so nothing too spectacularly accurate, Ill experiment and post the results.
you could put a thick coat on. You can also use plastilene (I have left some in the space, it is re-usable)