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Sealer under epoxy coating10/25
I am building quite a few cypress and poplar table tops to be finished with Glaze Coat epoxy coating. I poured one this evening and the results are pretty good but I spent a while popping air bubbles with a propane torch and the bubbles keep coming. I am trying to eliminate, or at least improve, the air bubble issue. I understand from the instructions you can apply a seal coat of the epoxy, but you have to wait several hours for it to dry before the full coat can be applied. I'd like to know if there's a faster way of sealing the wood before applying the epoxy. Has anyone tried spraying vinyl sealer, or any other fast-drying sprayable sealer, before applying the epoxy?
The trouble is, if you are trying to fill open grain with a fast drying sealer, they will either crack from excessive build or will keep slower solvents trapped in their film and will prevent the epoxy from curing correctly.
You are better off using a grain filler, then a coat of a shellac or nitrocellulose based sealer before applying epoxy. This method will take "several hours" as well.
I would do a test panel on a sheet of maple plywood. Zinsser Sealcoat shellac. Let it dry for at least 2-4hrs. If it clogs sandpaper then it hasn't cured long enough. There should be no interactions between the epoxy and shellac. Epoxy will stick to just about anything. Anything will stick to shellac.
You can massively increase the curing time of epoxy by preheating the resin. Leave a sealed metal can(quart?) of resin in a 5 gallon bucket of hot water out of the tap. Mix the hardener in when you are ready to apply it. It will cure faster. It will be half as thin. Very runny. It doesn't effect the cured physical properties of epoxy. The other trick is to simply heat up the room. The hotter the better. Mix the resin in metal cans will speed up the reaction as well.
I've only done one epoxy tabletop. I've bathed in a few 50 gallon drums of the regular stuff.
Adam: good advice. I would use de-waxed shellac, though. The wax in regular shellac can prevent some finishes from adhering to it.