Finishing scales using epoxy resin
Originally posted by cannonfodder in this post.
I have seen references to a lot of wood finishes for custom scales but I have not seen any discussion of epoxy resin finishes, so I thought I would start one. Resin is super hard and very easy to work with. It seals the wood and fills in any defects all in one coat, or rather pour. A single coat of epoxy is equivalent to around 50 coats of lacquer, it is probably close to the same coat quantity for CA and a heck of a lot easier to put on.
Left to right, blood wood, purple heart wood, stained oak and walnut.
The key is to get your resin and hardener mixed in exact proportions and thoroughly mixed. I use medicine measures for my mixes. I use to use a 0.1 gram scale but the resin and hardener are of different densities so weight measurements are problematic. A volume measurement works best for me. The problem most people run into (aside unequal proportions) is insufficient mixing. The resin must be thoroughly mixed. I mix the resin/hardener for at least 3 minuets with a small wood scrap. You have to make sure to scrape down the bottom and sides while mixing so you do not end up with a little blob of unmixed finish which will leave you with a tacky, sticky finish.
You also need to properly prep your wood. After sanding down to 400 grit and at least 4 hours (24 is better) before you want to pour the finish, wipe the wood off with a clean cotton towel that has been lightly moistened with a splash of turpentine. The turpentine will lift out any remaining dust in the wood pours as well as remove any oils left behind by your hands.
You will need a special work surface for the pour. You will need to suspend the scales so the resin can drip over the sides. I cut some small dowel rod into one inch lengths and glue them to an old hunk of cherry wood. Those will be my stilts to hold the scales up during the pour and curing process. I use two stilts per scale, one at either end of the scale. I use a small square of double stick tape (wood working double stick, not double stick foam tape) to hold the scale to the stilts.
Epoxy resin is ‘self leveling’ and does not need brushed on, although I will occasionally brush on a base coat if I am using a particularly oily wood or a stained wood. After the light basecoat brushing, I pour the rest of the resin on the wood. Slowly pour the resin up and down each of the scales. Be generous, the resin will run off the sides and drip down onto your base. I usually poure two or three passes on each scale. Once I have the first pour on all the scales I go back to number one and pour another, continuing until I have run out of mixed resin. That ensures that I have gotten even and complete coverage. Then walk away. Don’t poke/prod/fuss over them, just go away. The resin will take care of itself.
A day later you will have a glass smooth and high gloss finish, with the exception of the drips under the scales. I give the finish 2-3 days to fully cure and harden, then I take each scale to the garage and hit the drips with my bench grinder. That resin is hard, if you try to hand sand it off, you will be sanding for a long time. After I have ground the drips down on the bench grinder, I will hand sand the remaining nubs down.
If you have any dust specs in the finish you can use some 000 steel wool to level out the finish. The steel wool (or wet sand) will dull down the high gloss finish. You can buff the finish back. I give the scales two light coats of high gloss polyurethane to restore the shine after a buff. The backs of the scales need a coat to seal them. You can mix up a small batch of resin and paint it on, or use several coats of urethane to seal the wood. The urethane is easier and what I use.
In summary, you need a prepped finishing surface, sanded and prepped scales, a properly proportioned and mixed epoxy resin, 3 teaspoons of resin and hardener (6 teaspoons total) is enough to do 3 sets of scales (maybe 4) and pour your finish. Once hardened, grind off the drips and apply a back coat. Your are finished, no rubbing, no sanding, no 5 days of applying 20 coats of that other finish.
Almost forgot, durability? You can pound on a resin finish with a hammer and it will be no worse for ware. If you get a scratch in the finish, steel wool it out and buff the gloss back in. If you want a durability demonstration, I can pound on a resin coated board repeatedly and video tape it if you really want proof. I doubt you will ever damage the scales.