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I think polyester is much more scratch resistant, but if you spray, sand, and buff it out thin, it's not scratch-proof.

As for the MEKP issue...well, I mix a maximum of about 18 oz. at a time, and that takes all of 9 milliliters of MEKP which I dispense with a medicine dropper. We don't slather on gallons of this stuff like the surfboard or boat builders do. Two to three ounces of poly thinned 25% with MEK takes care of a coat on a typical full guitar.

[QUOTE=Todd Rose] Bob, thanks for sharing your experience. That's helpful.

So, a polyester finish will withstand the scraping of a pick without showing a scratch to the finish, but if there's enough force behind the pick to indent the spruce as somebody thrashes away...?[/QUOTE]

No finish will stop much of any force that would dent a guitar top, or at least not in any reasonable thickness. The only thing a harder finish prevents is wear, but I think that a belt buckle just scraping a bit rather than dinging against the guitar might just do a bit less damage with a harder finish.

_________________
Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

[QUOTE=Rick Turner]
UV light is a big deal.   You need full eye protection if you're not going to do a closed box system, and you need a lot of UV power to cure poly effectively.   You also need very specific bandwidths of the light. Getting it to cure evenly on a 3 D surface like a guitar is not easy.   If you're going to do this, call Kevin Ryan or someone who has actually done this before you go thinking you can beat the price barrier.
[/QUOTE]

I'm not sure if I'm reading this right, but I'll answer on a certain assumption because it might benefit others reading.

The UV lights involved do need a lot of juice to kick the finish in a short time, but the stuff will cure if you leave it outside on a sunny day.

A 4" lamp will cure a guitar but it'll take forever, a 6" lamp is reasonable for a small shop, and you'll want an 8" if you're going to be doing any quantity at all. An 8" takes between one and two minutes to do a guitar. There's a certain wattage per inch you need, which I don't recall off the top of my head. The company supplying the finish will tell you what wavelength light cures it most effectively.

As for pricing, a close friend of mine is a bit of a specialist in this area so I know for certain that the lamps can be built and sold at a healthy profit for much, much less than the companies in the industry are selling them for.

As for the UV light, you're absolutely right on the danger. Exposed skin will burn -real fast- around one of these lights. I always prefer the risks I can see to those I can't, and being a mouth breather I'm a real hazard around solvents

_________________
Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

If you're seeing UV, you're in danger of going blind. That's bad, bad stuff for your eyes.

we can see the mist, and we can taste it, anfd if we see it and taste it, we're in danger, but we can also eliminate that danger. Lightwaves, on the other hand....

I now have a pressurized head gear outfit feeding me fresh, filtered air at all times, plus i still wear a full respirator inside it, just in case the line should come off, power fail, etc.... Combined with a good booth and strong fan, then with the fast and complete off-gassing, I feel perfectly safe.

there are still plenty of nasty, nasty chemicals used if you use UV, and if you're having to handle the instrument, or light, for a few minutes to cure it, you've increased your exposure levels by a lot. With the MEKP cure, you shoot, and get out, in less than 2 minutes, tops. With my setup, I remain pressurized until exiting the building. Tres safe, methinks......

As for wear, i'm measuring(at the bridge area, when i strip, by saving a chip), between .002 and .003'', total. It shrinks with the top, it dents readily and if you play hard, it will show 'pick tracks' instead of scratches. This finish is so much more flexible than nitro, the denting is a given. How flexible? I can peel off .010" of finish(multiple sessions' worth) off the soundhole plugs, and wrap them around a pencil, and rarely will they break. Sweet! Flexible, yet scratch/scuff resistant to no end. What's not to love?

Back to deep lurking....

Does any one know if Tony F offers Cat Poly finshes?

Mr. Grumpy sounds very wise, and vaguely familiar. Could it be M...nah, but it sure would be nice.      

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Eagles may soar, but weasels don't get sucked into jet engines.

I'm playing with a new 2 part finish, it cleans up with laqure thinner! 24 hr cure time.
Lance

Lance, tell more.

Grumpy, stop lurking and come back. By the way, did you ever try the
Ilva polyester?

Has anyone used the Ilva polyester?

_________________
Mike

"The Dude abides. I don't know about you but I take comfort in that. It's good knowin' he's out there. The Dude. Takin' 'er easy for all us sinners. Shoosh." The Stranger

[QUOTE=McCollum] I'm playing with a new 2 part finish, it cleans up with laqure thinner! 24 hr cure time.
Lance[/QUOTE]

OK, I'm waitin' to be educated!! Seriously, I'd love to hear a bit more about this.

Bill

_________________
Eagles may soar, but weasels don't get sucked into jet engines.

[QUOTE=grumpy]As for wear, i'm measuring(at the bridge area, when i strip, by saving a chip), between .002 and .003'', total. It shrinks with the top, it dents readily and if you play hard, it will show 'pick tracks' instead of scratches. This finish is so much more flexible than nitro, the denting is a given. How flexible? I can peel off .010" of finish(multiple sessions' worth) off the soundhole plugs, and wrap them around a pencil, and rarely will they break. Sweet! Flexible, yet scratch/scuff resistant to no end.
[/QUOTE]

Hi, Grumpy. Good to hear from you.   

Thanks for chiming in with your observations about the performance of polyester film. For me, this puts more pieces of the puzzle into place, which is very helpful.

Let me see if I got what you said:
1) You're able to apply the finish to a film thickness of 2 to 3 mils.
2) It is highly scratch/scuff resistant, showing "pick tracks" rather than scratches* (see below).
3) It is very flexible.
4) It dents readily** (see below).

Another thing you said is that it "shrinks with the top". I'm not sure if I understand what you mean by this. Can you elaborate/clarify?

*Can you describe what you mean by "pick tracks"?

**Okay, it's flexible; it dents readily. If I understand what you're saying, it seems that one could say this: it doesn't provide any more protection than other finishes against dings or indentations from picks/jewelry/microphones, etc, that may assault the spruce. This isn't saying that it provides _less_ dent protection than nitro or other finishes, but not more either. The difference is that (like Rick said) it will move with the spruce and stay intact, rather than cracking or chipping or delaminating as another finish might. Am I getting this right?

It sounds like we're describing a finish that is very _tough_, but not necessarily very _hard_. Is it, in fact, tough but not so hard (like urethane)? Or is it tough, flexible, AND hard?

Thanks again. Your contribution is much appreciated.

_________________
Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

I realize that this is off topic a little, but with all you guys chiming in it seems like a good time to ask. What are the benefits of these finishes in relation to an oil over shellac finish? Specifically a tru-oil or a waterlox over a thin shellac coat. Is it tradition, or better dent resistance? I have looked through the archives but can't find a direct comparison topic between poly and oil finishes. Thanks,

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Burton
http://www.legeytinstruments.com
Brookline, MA.

Poly is tough and hard, but if you work it thin, it will move with the wood.   The guitar I finished last week...started on the Monday before H'burg and rubbed it out on Thursday...is showing nice spruce grain lines telegraphing through the (probably 4 mil) top finish. Personally, I love this look, and I think it demonstrates that the finish is nice and thin.

BTW, I glue my bridges directly to the polyester finish with thick superglue...that's how good the adhesion is of the finish to the wood.   I carefully wipe off any residual buffing wax with superglue solvent, and I also clean the underside of the bridge really well with acetone. Glue and clamp for about 30 minutes (probably overkill), clean up any squeeze out with superglue solvent, leave it another couple of hours, and string it up. Sure is easy...and there's no wondering if I have a perfect glue line...it is.

[QUOTE=Rick Turner] BTW, I glue my bridges directly to the polyester finish with thick superglue...that's how good the adhesion is of the finish to the wood.   I carefully wipe off any residual buffing wax with superglue solvent, and I also clean the underside of the bridge really well with acetone. Glue and clamp for about 30 minutes (probably overkill), clean up any squeeze out with superglue solvent, leave it another couple of hours, and string it up. Sure is easy...and there's no wondering if I have a perfect glue line...it is.[/QUOTE]

Wow. That would certainly simplify the process, eh? I had no idea poly was that good. I'm betting there's going to be a few poly converts after this discussion is through. Thanks Rick!

_________________
Eagles may soar, but weasels don't get sucked into jet engines.

Thanks, Rick, for continuing to share your knowledge and experience with polyester.

Speaking of CA glue, one guitar builder I've spoken with who uses polyester says that CA glue works well for minor repairs of dings and such.

This gets to one of my other main concerns with starting to use polyester. In my case, I will not, in the foreseeable future, be spraying polyester myself. I will continue to FP and varnish in my shop, and if I do start putting polyester on some guitars, it will be farmed out (to Addam, most likely). So, then, I get a guitar back from Addam and I manage to put a ding in it during set up, or it gets dinged at a guitar show. Without being set up to work with polyester in my shop, can I make that ding disappear (or become so hard to see that, for all intents and purposes, it has disappeared)? Is CA glue the answer?

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

CA is the ding repair for polyester.

Make sure you thoroughly clean the ding and a bit of the surrounding area, though, to get rid of any residual buffing wax or polish.   I use "industrial strength" Q-tip-like cleaning swabs I get from Mouser Electronics. They don't disintegrate like cotton Q-tips do.   Clean well with superglue solvent.   Don't use accelerator unless you want to see white bubbles...

The fix won't be absolutely perfect, but it won't get worse with time the way nitro lacquer touch-ups do unless you have a couple of months to let it settle.   

Make sure Addam knows you want poly. He does a great job, but mostly folks send him nitro work to do.

Hesh, I have no idea if it would work with your finishes. I started doing it on my Renaissance series upon the suggestion of Jean Larrivee. On those we do put a couple of screws and the strings load through the body, but after doing several hundred and having to take a bridge back off a few times, I gained a lot of confidence that it would work on my acoustics.

I use fresh "Super T"...the orange label medium viscosity stuff that I get from LMI. We keep it refrigerated until we open the bottles and then keep them capped. I do clamp a well fitted bridge so the glue line is very thin and even; I'm not looking to fill any gaps at all.   As I said, I de-wax the top, and I wipe the bridge bottom with solvent or acetone to minimize oils. With the polyester I can use solvent to clean up any squeeze-out with absolutely no damage to the finish.

Short of actually inlaying the bridge into the finish or doing the little rabbet all the way around the bridge and inlaying into a routed-through-the-finish spot, I don't think you can get better bridge to top fitting than this way. There is 100% contact between the bridge, the glue, the finish, and the top. The finish sticks to the top amazingly well, and the bridge sticks to the finish just wonderfully.

I fit the bridge to the top by sanding with self stick 150 grit sandpaper lightly adhered to the top. When I clamp it in place I'm not forcing anything; I'm just trying to get a nice thin and even glue line.

Sure is quick and easy...

Thanks for the lowdown on using CA for polyester ding repair, Rick.

Now, thinking a bit beyond a little ding that might happen before the guitar is in the customer's possession...

Do you recommend CA for finish repairs on polyester in general - work that goes beyond drop filling a ding? For example, say I get a guitar back for a warranty repair of some kind that includes touching up the finish. Is it just as well that I continue to use CA, or would I be better of equipping (and educating) myself to work with the polyester finish material itself for future repairs?

_________________
Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

[QUOTE=Rick Turner] ...is showing nice spruce grain lines telegraphing through the (probably 4 mil) top finish. Personally, I love this look, and I think it demonstrates that the finish is nice and thin.[/QUOTE]

YES!

[QUOTE=Robbie O'Brien] [QUOTE=Rick Turner] ...is showing nice spruce grain lines telegraphing through the (probably 4 mil) top finish. Personally, I love this look, and I think it demonstrates that the finish is nice and thin.[/QUOTE]

YES! [/QUOTE]

I like that look as well. After seeing the Asian imports for years that have that thick plastic look I became nauseated by that appearance. Grain line texture = thin finish.

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JJ
Napa, CA
http://www.DonohueGuitars.com

    Although I love the look of the lifted grain lines in a Spruce top being
visible and tangible through the finish, it isn't an indication of a thin
finish alone, but also of a top that has been affected, post build, by
humidity.

   A very thin finish can stay perfectly flat and glass like for decades if the
top is stable and the resins are set. I've cooked all of the tops that I've
ever taken into my shop to set the resins in the wood to avoid that effect.
I like it in a prewar HD-28, but not in my new guitars.

    The reason that I strive for the longevity of a perfectly flat surface is
simply for longevity of the integrity of the finish itself. If there are
protruding grain lines, pick passes can be absorbed by those higher lines
and can much more easily break the surface of the finish. A smooth
surface is more difficult to pentrate with those pick strokes than one that
exhibits a texture or pattern of lifted grain line running paralel along the
top's length.

   My UV cured poly finishes end up as thin as any lacquer applied to a
guitar and stays perfectly flat. At .004" to .006" thay can appear much
thicker to the eye because of it, but they're just as thin and light as any
finish that has followed the surface of the wood under it as it's affected
by humidity and allowed to move. Another point to consider is that many
builders have piled on the lacquer to thicknesses exceeding .010" over
the years and this thick finish still follows the texture changes in the top
wood...even tho it's thicker than I'd recommend.

   The lines are indicative of more than a thin finish is my whole
point...and not always a desirable thing.

Regards,
Kevin Gallagher/Omega Guitars

Thanks Kevin...I stand corrected. I've cooked some tops and will look for the difference in the future.

_________________
JJ
Napa, CA
http://www.DonohueGuitars.com