Finish Test Project

[ScottR]

I decided to test out a couple of finishing products/techniques as I have this need to have projects, but am not quite ready to begin my next guitar. One was Tru Oil, as I really like the way it looks when done well on this site. Mostly Quarter's exquisite lap steels come to mind. Gun stocks look nice too. The other is Z-Poxy which is mostly used in our world as a grain filler to the best of my knowledge. I have used it in that capacity and I have used it to fill the eyes of my bear carving. As bear's eyes it polished up like glass. I'm wondering how close to Rustin's plastic finish it is.

I had a piece of fire wood I had been saving back for a couple of years because it appeared to have a nice curl in it. It also had some spalting. I sliced a slab about an inch thick out of it and sanded the sides down. The curl didn't show up as well as I'd thought it would. It did show some burl like figure here and there. The spalt looked nice. Here are the two sides before I applied any finish.

Then I proceeded to apply Tru Oil to one side and Z-Poxy to the other. The Tru Oil is going on and building up about the way I expected. The first coat of Z-Poxy went down nice and cured up hard. The second coat cured up very nice and shiny; it looked like a bar top, but it was some what soft. I polished it anyway, while going though the Process up building up the Tru Oil. It polished nicely but marred too easily. So I tried a couple of experiments. You are supposed to mix equal amounts of resin and hardener and it is supposed to be forgiving enough to mix by eye. Since my last batch was soft I mixed a small batch with a bit more hardener than resin. It came out soft and slightly sticky. So I mixed up a batch with more resin and less hardener. This came out rock hard. That seems counter-intuitive to me. Has anyone else come across this phenomena as well?

I sanded off the soft layer and mixed the next two at roughly3/2 ratios of resin to hardener. It has a longer working time and flows out fairly nicely and the nearly all the bubbles pop. Here are the sides in the middle of the process.

This side has Z-Poxy

This side has Tru Oil.

When they are completely finished and polished I'll through the final pics.

SR

[Woodenspoke]

The final polish will the kicKer for me. Cant wait.

[Mender]

You are supposed to mix equal amounts of resin and hardener and it is supposed to be forgiving enough to mix by eye. Since my last batch was soft I mixed a small batch with a bit more hardener than resin. It came out soft and slightly sticky. So I mixed up a batch with more resin and less hardener. This came out rock hard. That seems counter-intuitive to me. Has anyone else come across this phenomena as well?

Yes, this is quite common with all brands and types of epoxy I've used, including epoxy adhesives.

Some epoxies even have that stated in the instructions

[ScottR]

Huh. I'm still learning something new every day. I wonder why it works that way. One would think that more hardener would come out more harder...if one didn't know any better.

SR

[supplebanana]

nope... it's the resin that goes hard - the hardener is the catalyst/activator, too much of this will soften the resin.

[Buter]

Howz this going, Scott?

I've got kilos of super clear epoxy and some nice, soft walnut that would benefit from your tests.

Yeah, epoxies are not very tolerant to getting the ratios wrong. In most high end surfboard shops, the resins and hardeners are measured on very accurate digital scales.

Just as an aside, epoxy finishes are notoriously difficult to polish to a finish that would be acceptable for a guitar finish. I'm not saying that it cannot be done, it just wouldn't be done when you're trying to do 3 or 4 surfboards in a day. Spraying a clear coat on top of levelled epoxy might be an idea, but it might defeat the point of your excercise.

Keep us posted.

Cheers

Buter

[ScottR]

Howz this going, Scott?

I've got kilos of super clear epoxy and some nice, soft walnut that would benefit from your tests.

Yeah, epoxies are not very tolerant to getting the ratios wrong. In most high end surfboard shops, the resins and hardeners are measured on very accurate digital scales.

Just as an aside, epoxy finishes are notoriously difficult to polish to a finish that would be acceptable for a guitar finish. I'm not saying that it cannot be done, it just wouldn't be done when you're trying to do 3 or 4 surfboards in a day. Spraying a clear coat on top of levelled epoxy might be an idea, but it might defeat the point of your excercise.

Keep us posted.

Cheers

Buter

The Z-Poxy side is sort of waiting for the Tru-Oil side to get enough layers built up to level and polish both at the same time. I think it will get done this weekend. I thought the last coat of z-poxy was acting differently from the others or was contaminated at first. It had the same lower hardener to resin ratio as the others (that came out so hard) if not a little more extreme. After 12 hours the surface still scratched with a finger nail. The next day it had completed curing though and was/is rock hard. I have been using epoxy as features in eyes or crack filling in my carvings for some time now, and never really knew why every once in a while I'd get a soft mix. I always tried to keep both parts equal, but I did mix by eye not weight, and would err on the side of extra hardener when in doubt. Now that I've been educated I shall err the other direction. I will say that every mix that came out superhard would polish up like glass. I have never done a surface large enough to get an idea of how it would work or look as a coating. It would definitely create some extra work leveling as compaired to a spray finish.

This Z-Poxy claims to be a polyester based finishing resin. What is the surface of products made from molded fiber glass composed of (gel coat?). I'm seeing some similarities.

SR

[stereordinary]

Fascinating test, I'll be sure to watch where it goes as well.

[Buter]

Gel coat is just a nice name for a pigmented finishing resin. I've only ever heard it referred to in boating/yachting circles.

For surfboards it's referred to as a hot coat.

[ScottR]

I sanded back into the wood on the Tru-Oil side. Apparently it was not as thick as I thought. So I have begun re-coating that side.

The Z-Poxy side polished out nicely. When I started, the surface looked very slick but a little wavy, especially where the resin flowed off the irregular edges. It looked much like a poured bar top finish. I leveled it with 150 grit and ran up through 600. Then I moved on to micro- mesh and went through all the grades up to 12000. Finally a turtle wax polishing compound took all the swirl marks out. It left a very hard, very reflective surface. I did drop my sanding block on it and the corner left a small ding. I think the same thing would have occurred with any finish that I have used so far, but this does tell me it is not bullet proof. It also does leave witness lines like polyurethane does when you sand through the layers of applications. They only show if you angle it to the light just so, but they are present. Another thing I noticed is that the finish has shrunk into the grain very slightly over night. This was not visible at all when I started leveling and the last coat of Z-Poxy was applied two weeks ago. I would have thought it was done curing, but perhaps the fact that I used less than the recommended amount of hardener has slowed down the cross linking (curing).

So would this be a viable finish? Yes, I think so. Is it any better than the other finishes being used? No, probably not. Man it does look good though.

I'll throw up some shots of the Tru-Oil side when I get a decent finish accomplished.

SR

[Mender]

That's an incredible finish, just like a mirror