Greetings! Newbie here...
I bought the beginners laminating kit which included the PVA release agent. The mould tool was made from Polystyrene with a wooden support, painted with (car) cellulose paint (thoroughly cured). I did wot it said for the release agent, but it didn't release. Sob, sniff. The paint came away in chunks. Wot a mess.....
Any ideas of what I did wrong? Be kind.....
Should I be using the wax release agent? If so, why is there PVA release agent in the kit?
I'm about to start reworking the tool for another go and would prefer to get it right this time!!
For scale, the finished parts are about 150mm amd 100mm long.
TIA

Andy Ricketts

It sounds like the paint has outgassed through an uneven layer of PVA.  PVA is normally ok as it provides a barrier.  However if the PVA isn't quite even then that could cause issues.  Also sometimes if the resin is a little green it grips the mould harder so would likely rip off a weakly attached paint - polystyrene doesn't offer the best bond. 

We tend to recommend avoiding using paint on moulds or patterns for that reason.

I would imagine once those parts are fully cured, the paint will wipe off with acetone.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

+x

 

Andy Ricketts - 8/11/2020 3:07:52 PM

+x

 

Warren (Staff) - 7/16/2020 1:26:21 PM

It sounds like the paint has outgassed through an uneven layer of PVA.  PVA is normally ok as it provides a barrier.  However if the PVA isn't quite even then that could cause issues.  Also sometimes if the resin is a little green it grips the mould harder so would likely rip off a weakly attached paint - polystyrene doesn't offer the best bond. 

We tend to recommend avoiding using paint on moulds or patterns for that reason.

I would imagine once those parts are fully cured, the paint will wipe off with acetone.

.....But if the mould IS painted with a fully cured cellulose paint, what release agent should be used? The recommendation in the videos is to only use one layer of a PVA release agent, additional layers just move the previous layer to no advantage and that clearly does not give the required release result. So, what release agent should I be using?

Currently I have wrecked moulds, made of several styrene parts, glued together and with styrene filler, all sanded smooth...I can repair them and return them to the original state (with or without paint) what is my recommended course of action? And then, what release agent to use?

If PVA doesn't work nothing will. I would recommend making some small scale tests and check compatibility. I would have guessed that PVA should work as long as you have a an even layer as suggested before. It is possible that you messed up the PVA film while laminating as well. So careful there.

If you can spray the PVA, then you can build up layers and you can release off virtually anything. If you don't have equipment to spray, have a look at Preval sprayers. They will work very well for applying PVA.