About a week ago I was working on another music stand. I already had one pour of System Three Mirror Coat on it and waited the recommended time to do the flood coat. It went on fine and I covered it to dry. It was beautifully smooth and a perfect finish. After the drying time had passed I turned the easel over and with a random orbital sander I removed some of the dried dripping from underneath the edges. When I turned it back over the the perfect surface I had, now had 400 or 500 air bubbles about the size of the top of a pincil eraser. I found out later between the two pours. The two pours had separated I assume from the vibrations of the sander. I had to remove the layers with a chisel over a span of three hours. I can’t think of any reason other than vibrations from the sander.
This is a typical problem with Epoxy finishes .one to way to get rid of bubbles is to blow on it when it’s wet or a fine mist of denatured alcohol, all you can do now is sand and re-coat.
If possible it’s best to warm up what you coating and apply the epoxy as it’s cooling down,that will help it out gas.
woodworking classes, custom furniture maker
Unless you could get away with pouring the second while the first was [very slightly] tacky, it would seem sanding, for adhesion, would be a must, just like with poly.
Sounds like you’re right. It wasn’t a matter of air transferring from the wood into the pour, since the first was already dry and, rather, a matter of the second layer breaking loose from the first.
For my old 50-50 resin mixes, which I bought in two five gallon containers at a time, sealing the wood was critical for the initial pour, to stop air from escaping the wood into the resin. After the pour, I’d flash it with a torch, which drew the few bubbles that remained out. Obviously, many finishes can’t be done that way, least you find yourself on the other side of a wall, without having gone through a door.
I should note I had this problem with SOME pours when I poured over brass on wood, but only some times. It may have been a temperature difference too. The resin lifted around the edges of the brass, where it met the wood, but not off the main surface.
Epoxies (even filled adhesive mixes) generally cure to a hard glossy surface that needs sanding to give a second coat something to “bite”. Also most (not all) epoxies have an amine blush that must be removed before re-coating with anything. Do the instructions say you can recoat over a cured, unsanded first coat?
The early bird gets the worm but its the second mouse that gets the cheese.
Thank all of you guys for the ideas and experiences you have had with epoxy coatings. 95% of the bubbles burst upon application of both coats and after about 10 minutes I waved a torch over the surface and got the rest of them. Paul the base coat was crystal clear and the instructions say nothing about sanding before the flood coat. I have since repoured the piece and it seems fine so far. I did buy a new supply of epoxy fearing the possible of shelf life on the first bunch. Thanks again to all.