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I spent the better part of 5 hours doing the final sanding on the harp guitar. It had a thin coat of squeegeed zpoxy. While still wet , I used a razor to further press into wood and clean up.

Does this stuff wick in very far? Here is what I noticed. To achieve even color after use, I had to sand quite a bit. To me, it seems like i have sanded off all the zpoxy. If so, how would I know when to stop? (other than no surface appearance of the material) Do I need to reply? Did I not have the surfaces flat enough for first application?

I will add that the wood "seems" harder. And after sanding back to 220 grit, it is smooth as silk. BTW, the hardwood is Bubinga. Just wondering if I wasted my time with the zpoxy.

Cutting binding and channels tomorrow.

Mike

Mike buddy I sand back with 220 and you can sand back to the wood or leave a uniform epoxy film.

It sounds to me like you sanded back to the wood like I did in my toot. My sample piece does seem silky smooth too and as long as the pores are filled you are in good shape.

If you want the epoxy film on the entire surface mix Z-poxy finishing resin 50:50 with denatured alcohol and wipe a thin film on the entire surface, this will even out the color. Or just sand back to the wood leaving it only in the pores.

Well Hesh, seems an interesting problem. I thought I had sanded well before I applied the zpoxy, but it turned out I did not. And how I knew was some color "banding" that happend as I sanded the top. Since the zpoxy is darkish, the lops of the "valley ridges" would sand down leaving a dark, wideish "valley" bands. Does this make sense? So I kept sanding till all was uniform.

Since the zpoxy is so hard, I think next time I will first spray with dewaxed shellac (bought some of the EmTech 6000 water born lacquer) then sand back to wood, using the coloration as a clue to how well I am doing. Then, apply a thinned coat of zpoxy as you suggested. Out of the tubes, the stuff is too thick to my senses. Yes, I will do a thin wash of zpoxy... given the amount of sanding (aggressive) I did, I am going to make sure the pores are filled.

BTW, I use a small B&D palm sander (mouse. love that thing!). I tried the Big Mouse and forgetaboutit! The little mouse is better for control. I read in FWW about the highend orbitals (Festool, etc). Are they better and worth the $$? What about for sanding the waist? (that is SO difficult). Thinking about making an attachable form for the palm sander to work the waist area better.

BTW, I do not want the epoxy film... I do not want the color.

Mike

Mike,
If you don't like the color of the epoxy, then why not just sand all back to wood, and then use the shellac and wood dust trick. If you have light bindings, cover with thinned lacquer using a q-tip to protect it from getting stained. Don't forget to cover the back strip too if you have one. Then dump some end grain dust the same wood as the back and sides in 1/4 of the back. Use a cotton ball soaked in shellac to rub the dust into the pores. Try not to put too much shellac on the cotton ball. If you want no pores showing, then wait an hour, and sand back, and repeat. Wait a day or 2, then repeat. Shellac does shrink back, so if you wait a few days or even weeks you will get better results. Good luck!

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Tracy
http://www.luthiersuppliers.com

Well, it was my second attempt. Live and learn. I think the wash trick might be the ticket. I will also consider the dust, shellac approach. Yes, I have been following the other threads on this topic. I was really suprised at how hard the epoxy was. It appears to really harden the wood down to some depth.

My problem on the harp was that the whole body was not sanded and scraped fully when I applied the epoxy. But I did not know this till after the epoxy. Thus, I think a thin coat of shellac might be useful in determining that the sanding was done properly. And shellac hurts nothing. Also, after the sanding, a new coat can be applied for final pore fill. I am not convinced that dust filling is good as wet dust looks darker... so the pores, though filled, will be darker. And then there is the issue of chatoyance. I would not want the dust to inhibit that. Bubinga with figure is amazing under finish.

Filippo,

Yes... that is the case. I thought I had everything sanded flat, but I was wrong in that assumption. Now, I am wondering how anyone could know that for a fact without some kind of "tracer marker." One could accomplish this with any kind of "paint." But since so many use shellac as a sealer, this would be the obvious choice. Enough marking contrast with sanding. Then reapply (or use zpoxy given its hardening and pore filling qualities.)

My guess is that a lot of builders use some kind of technique similar to this to assure flat surfaces. It makes sense.

Mike

Mike buddy two things to keep in mind:

First shellac will stick fine to epoxy but epoxy will not stick as well to shellac. Both Michael Payne and I have experienced this and we both tend to beat the dead horse saying this often on the OLF.

Second surface prep is super important prior to applying finish and pore filling. Having the sides block sanded flat is very important before cutting the binding channels. It's all related to how the finished guitar will look when completed.

And even though I said two things I'll throw one more in to consider. The light that we use in our shops - may - hide scratches in our final sanding that will become scratches under glass if we don't notice them prior to starting the finish process. Some ROS's and even thickness sanders can leave some scratches that I have a very hard time seeing.

The fix is to closely examine the entire guitar under various types of light and not just your shop overheads and this usually reveals what needs further attention.

Regarding your question about sanding the waist area I use a 1" X 8" hardwood dowel with self-stick 120 3M paper on it. A larger diameter dowel would be better IMHO I just have not found one yet.

Good luck.

For surface prep, raising the grain a few times will help with your surface problems in a couple of ways.

Raising the grain means lightly wetting the wood, letting it dry, and then sanding back all the littly hairs that have raised up from the moisture.

A big benefit is that when you wet the wood, all of the little scratches and imperfections that you could not see while the wood was dry, but will stick out like crazy once the finish goes on, become easy to spot.

You can also wipe on some solvent, like mineral spirits or alcohol, it wont raise the grain, but will show you your surface well(watch out for alcohol on rosewoods though).

The water or solvent will wick deeply into any scratches or imperfections, making them show up very dark and easy to see. Pore filler and finish will also darken imperfections, but it sucks to scrape and sand back to wood once you have finish on.

Raising the grain two or three times also gives you a nicer surface.

Also what Hesh said, it helps to look at the guitar in a variety of lights VERY critically.

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Jordan Aceto
Ithaca, NY

Good tip Jordan! I raise the grain on necks as you described and find that it can even help even out the color in the heel area a bit. But I never considered if for the body....

Hesh ... try some 1.5 and 2 inch black ABS pipe for your waist and cutaway (if you have) sections... I pad mine with thin foam rubber, and thent he sandpaper .. the cushioning helps the paper last longer .. I also use the 3 inch stuff for rounding the sound hole.

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Great tip Coach Tony! Thanks!

Not to hijack a thread but I have some comments and a question that sort of fits here.

I did a sample test with some of the cut off wood from my cocobolo back and sanded back to wood on one side of the test and left a thin coat on the other side. As a devote coward I always test new products, as I don't like surprises. I like the look of the sanded back test better and when wet with naptha it looks quite good. I love the filling capabilities of epoxy over the other grain fillers I have used.

With the Z-poxy does anyone do anything to cover or protect the wood binding and purfling or can the epoxy get on these areas without causing issues?

Fred

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Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

To quote a master at epxoy filler"just sand the nubs off" I take that to mean a light sanding. I use some 400G paper, hold up to the light and dtermine if the epoxy has filled and leveled any gaps, then go for water base (KTM9) finish.

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Greg
http://garibaldiinstruments.com/

You might have to look at the reactivuty data in the MSDS. But that said, I do not think there are issues. What I have decided to do now is apply the expoxy before bindings and purflings are installed. This helps me avoid oversanding the bindings when the occasional surface error pops up. Later, it is no problem to apply a "wash" coat to the bindings. I did take Hesh's advice on a 50:50 ratio of D-alcohol and zpoxy resin. Used a cotton rag to rub it in.

Mike

Ever used one of these?

http://www.grizzly.com/products/7-1-2-x ... ders/H2882
I have the 1" model I use for necks. This is on the wish list.

Nice idea! I still think a bolt on form with curved surface would be ideal for a palm sander. I worry about too much stock removal.

Mike