Steve Sanford
Well-known member
Joe~
In recent years, I have been using epoxy from U S Composites - their 635 Thin Epoxy 3:1 with Medium Hardener ( http://www.uscomposites.com/epoxy.html ) I have not experimented with their other products because I always have some of the 635 in the shop.
When sealing wood - with no 'glass covering - I apply the epoxy with EITHER
a) For small pieces: throwaway bristle brushes (so-called "chip brushes - which I buy in quantity because they are so much cheaper that way). I try to get a thorough coating on all surfaces but do not "float" it on. I brush everything carefully before I hang it to cure.
b) For larger pieces: foam rollers. I cut a 9-inch foam roller cover in half on the bandsaw and use a small roller. The roller gives great control but sometimes a thinner coat. So, a third coat may be warranted.
If I can, I hang my work (over a piece of plastic or cardboard) so that the epoxy will run to one or 2 low points on the piece. I believe most epoxies get "wetter" as they go through the curing process. Basically, the viscosity changes - it gets less before it thickens again and hardens. As a result, it is really difficult to avoid runs or big drops that might need removal later. If you can, it helps to keep checking on the piece as it cures. Often I can wipe off excess without starving the coating.
A second coat can be applied without intermediate sanding IF applied when the first coat is tacky and almost dry. Sometimes this works. Other times. I may want to wait for a full cure so I can smooth the first coat before applying the second.
Smoothing epoxy can be done with sandpaper, a power sander or even a grinder. Wherever possible, though, I prefer to start with a sharp paint scraper. It is the best tool for flat surfaces and - unlike sanding or grinding - can be done before the first coat is truly hard.
If I am sanding the first coat to receive a second, I like to get it thoroughly cured. In colder months, I put it near the wood stove. In warmer months, the sun on the south side of my shop can make a big difference. If the epoxy is not fully cured, it will clog paper or discs in no time. Even if the scraper is my primary tool, there are usually edges et cetera that need sandpaper. I use paper in the 80- to 120-grit range.
The second coat is brushed out thoroughly and hung up and watched/fussed with much like the first.
The finished work is sanded with 120 or 150-grit paper. It is also a good practice to wipe it down with warm water and a ScotchBrite pad to remove any "amine blush" produced by the cured epoxy. The blush can prevent paint adhesion.
I have had good luck with oil paints - primer then 1 or 2 topcoats - over epoxy - but have read of others experiencing problems.
So: 2 coats with a chip brush or small roller, hanging to cure, sanding in between, sanding and wiping before paint.
One final note: If I am filling the weave on 'glass cloth, I use a combination of squeegee and foam roller.
Hope this helps!
SJS
In recent years, I have been using epoxy from U S Composites - their 635 Thin Epoxy 3:1 with Medium Hardener ( http://www.uscomposites.com/epoxy.html ) I have not experimented with their other products because I always have some of the 635 in the shop.
When sealing wood - with no 'glass covering - I apply the epoxy with EITHER
a) For small pieces: throwaway bristle brushes (so-called "chip brushes - which I buy in quantity because they are so much cheaper that way). I try to get a thorough coating on all surfaces but do not "float" it on. I brush everything carefully before I hang it to cure.
b) For larger pieces: foam rollers. I cut a 9-inch foam roller cover in half on the bandsaw and use a small roller. The roller gives great control but sometimes a thinner coat. So, a third coat may be warranted.
If I can, I hang my work (over a piece of plastic or cardboard) so that the epoxy will run to one or 2 low points on the piece. I believe most epoxies get "wetter" as they go through the curing process. Basically, the viscosity changes - it gets less before it thickens again and hardens. As a result, it is really difficult to avoid runs or big drops that might need removal later. If you can, it helps to keep checking on the piece as it cures. Often I can wipe off excess without starving the coating.
A second coat can be applied without intermediate sanding IF applied when the first coat is tacky and almost dry. Sometimes this works. Other times. I may want to wait for a full cure so I can smooth the first coat before applying the second.
Smoothing epoxy can be done with sandpaper, a power sander or even a grinder. Wherever possible, though, I prefer to start with a sharp paint scraper. It is the best tool for flat surfaces and - unlike sanding or grinding - can be done before the first coat is truly hard.
If I am sanding the first coat to receive a second, I like to get it thoroughly cured. In colder months, I put it near the wood stove. In warmer months, the sun on the south side of my shop can make a big difference. If the epoxy is not fully cured, it will clog paper or discs in no time. Even if the scraper is my primary tool, there are usually edges et cetera that need sandpaper. I use paper in the 80- to 120-grit range.
The second coat is brushed out thoroughly and hung up and watched/fussed with much like the first.
The finished work is sanded with 120 or 150-grit paper. It is also a good practice to wipe it down with warm water and a ScotchBrite pad to remove any "amine blush" produced by the cured epoxy. The blush can prevent paint adhesion.
I have had good luck with oil paints - primer then 1 or 2 topcoats - over epoxy - but have read of others experiencing problems.
So: 2 coats with a chip brush or small roller, hanging to cure, sanding in between, sanding and wiping before paint.
One final note: If I am filling the weave on 'glass cloth, I use a combination of squeegee and foam roller.
Hope this helps!
SJS