Final layer of mold plug?

I used a layer of spray paint sanding compound over epoxy on the mold plug, sanded to 1500 and then added wax on top. The tooling gel coat heated the spray primer and took all of it off when I pulled the mold off.

Can I pull a mold directly off epoxy (with wax of course)?

Or what would be a great material to use for the final surface of the plug since I don't have spray equipment? I can only brush

 

I'd gelcoat it, roll it carefully if you can't spray then you can sand her down a bit and then wax it plus use a mold release agent as well till the mold is seasoned

 

Cool I'm going to try that, hopefully rolling (plus tipping) will make it somewhat smooth to start sanding

 

So you wouldn't recommend pulling a poly mold from an epoxy plug?

 

Im sure you could wax epoxy, never tried it. When you wax your new molds, you need to do it like 8 times. Then use PVA or other mold release agent over that. After awhile the wax buildup will require less coats.

Im not an expert in molds, I'v just started using them myself, so maybe others will chime in with some tips.

 

The reason it came off has little to do with heat, very few primers (or paints) will hold up to the styrene in gel coat.

You can use the epoxy as a mold surface.

If you want to use something over the epoxy, use Duratec sanding primer, it will do a good job of bonding to the epoxy, and will be easy to sand.

 

If you use epoxy, make sure all the amines are washed off. They act as a cure inhibitor for polyester resins.

 

i second using duratec surface primer.

easy to use and sand and it polishes up nicely as well to take a mould from it.

 

Good info guys, can I roll/brush the Duratec surface primer on?

 

Yes, but it will still have some texture.

Sand the epoxy with 80 grit prior to applying the Duratec.

 

OK Good to know, I know Duratec sticks to a lot, but polyester not so much.

If I put poly gelcoat over epoxy it wont stick? Should I sand it down to 80 grit to make sure the gelcoat sticks? Because right now I have gelcoat and not duratec

 

Hard to say if it bond very well, too many variables.

 

Interesting I am going to try this tonight

 

aaronhl, it should bond well enough for the use if the epoxy was correctly mixed and fully cured. Wash it and sand it apply your gelcoat and make sure to wax is multiple times before you use it. multiple layers of wax will help prevent a repeat experience.

 

Yea this isn't a structural project just a quick surface to pull a mold off...I just rolled the polyester gelcoat on the piece after sanding at 60 grit. This is the first time I rolled gelcoat and it was pretty neat actually I didn't think it would come out that nice and smooth. Now I see why gelcoat is used because its really stickyyy and not too thick. Epoxy just runs and is pretty thick

If I want to build up a gelcoat surface, can I roll a coat, wait half an hour and roll another one, and so on? It seems like no matter how much gelcoat I loaded on the roller it wouldn't thicken the layer.