What to use to coat a foam plug?

I just finished shaping a foam plug (a combination of bead board, rigid insulation, and Great Stuff), then filled the surface with typical wall spackle. After some sanding and wet rag here and there, it's at the shape I want. Ultimately I need to pull a fiberglass part off it. What is the simplest thing I can coat the spackle with before waxing to ensure the part will release? Will a couple coats of varnish work, or some type of paint? Ultimately, I'll be using epoxy resin on the cloth. Thanks!

 

I used to coat "quicky" molds with shellac & then use wet & dry paper with wax then polish up a bit. All the best from Jeff.PS: You might wanna sponge on or spray some PVA release agent too.

 

PVE liquid release agent works quite good. It is important that the surface is absolutely 100% covered, so one layer is not enough. Otherwise the styrene in the resin will find the tiniest hole and eats your foam.

 

CDK makes a good point about styrene attacking the foam you've used, you might wanna check its resistance to alcahol too as the shellac & PVA have both got it, if the whole surface is "spackle" you'll probly be ok & you've mentioned laminating in epoxy which is ok with that foam. All the best in your endeavours from Jeff.

 

Hello Cornelis and Jeff!!! There is no styrene in epoxy................

 

What is PVE liquid release agent ? I tried to google for it...

 

apex is right, no styrene in epoxy. Easy to get too.

Not PVE its PVA.

 

If it is not a complex part you can wrap it tightly in polyethylene plastic. Then with heat gun shrink it down. Takes some practice to apply the heat with a heat gun so the plastic shrinks neatly without ripples. It will release without any other coating. Even if the plastic is damaged it is an easy job to recover for the next job. Plastic will also take out minor surface defects in the plug. Use duct tape to secure the plastic to the plug.

I have also used duct tape to completely cover a small plug. It releases OK if the edges are stuck firmly so resin does not get under it.

Rick W

 

Thanks for the answers, guys. I'll let you all know what I end up going with and how it works! Cheers!

 

If you spray PVA (polyvinyl alcohol - NOT POLYVINYL ACETATE) Just mist a coat, let dry, complete, or it will fisheye.

 

Of course there isn't, but only now I see he wrote epoxy resin.
And of course it is PVA, not PVE.

The ongoing heatwave and too much Weizenbier can do that to you.

 

Thanks for the advice Apex1, the original post mentions molding a part in epoxy cloth, of course the choices of making the tool off the plug is open to styrenated products or epoxy.
Nwwayoflife, as many paints/coatings contain solvents that will "fry" or dissolve some foams, its good to be carefull in checking on some offcuts the compatibility of materials as results could be dissapointing if it goes wrong. When you say "bead board" I'm assuming that its expanded polystyrene sheet, often called EPS in board making. Regards & all success to you in your molding endeavours from Jeff.