Official Luthiers Forum!

I was just curious what you luthiers preferred as a finish (nitro or poly) and why.

thanks.

Ken

French Polish!

Sonically the most transparent, and easily repairable. Plus as a builder I don't need a spray booth and other equipment.

Colin

PS I'm very biased, so take no notice

_________________
I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Ken,
   I sprayed hundreds of guitars with nitro lacquer and got great results
and typical durability and protection of that finish. Anytime, though, that
one of my guitars would come back into my shop after a year or more out
in the field, the finish would disappointment me because it had continued
down the same path of shrinking and pulling as on every old Gibson or
Martin that I'd ever seen.

   It's a wonderful finish and has been applied to some of the finest
guitars ever built, but technology in the finish industry has long passed it
in quality, durability, longevity and the level of protection for the guitar.

   I use UV cured poly now and have sprayed nearly 150 guitars with it
and couldn't be happier with the results...both on the day that a guitar is
completed and a few years later when it comes back into my shop for me
to see.

   It stays clear and is virtually ipossible to scratch since it is mutiple times
more durable and offers protection for the guitar that is equally superior.
There is no continued shrinking or pulling and the typical "vintage"
checking and cracking that occurs with nitrocellulose lacquer isn;t
present.

    Also, because of its greater ability to resist scratching and checking,
the poly can be applied as thin or even a bit thinner than nitro lacquer
providing an equal or greater environment for free vibration of the woods
under it.

Just my personal feeling and findings,
Kevin Gallagher/Omega Guitars

I've never seen nitro as superior to many of it's modern synthetic
counterparts in any area but one - serviceability. Organic finishes like
shellac and nitro are the only ones which can be amalgamated during a
repair or touchup. Once a synthetic is cured, it's cured.

Then again, a lot of the UV cured poly finishes can be touched up almost
seamlessly, given that you're set up for UV touchup. They won't resoften
like nitro, but if the surface is clean it doesn't leave terrible ghost lines.

Nitro is really inferior in almost every other sense to most modern
finishes. Still, whether it's a conditioned appreciation or otherwise, there
is something graceful and aesthetic about how a good organic finish
ages. A 40's J-45 just wouldn't feel the same if the finish were still
perfectly clear and uncrazed.

I don't know if that's reason enough to advocate use of nitro, especially
because it's a terrible finish for environmental and health reasons. Still,
something to consider.

_________________
Eschew obfuscation, espouse elucidation.

kevin, are you referring to polyester or polyurethane?

Kevin uses a UV-cured polyester finish. What I remember from Kevin's
posts is that it cures in 20 seconds, takes repair extremely well, and that
he had to sell his golf course to get started with it

I use catalyzed polyester, and I love it.   24 hours cure to rubout...that's fast enough for me at this point. Typical film thickness of around 5 to 6 mils, tough as nails.   I started finishing four instruments for Healdsburg last Monday, and we were rubbing out on Wednesday, and when I say "started" I mean epoxy fill, then urethane sealer, then poly top coats all done in two days starting on Monday afternoon.

The "repairability" of nitro is greatly overstated.   I've never seen a nitro repair that looks good after a year.   It always shrinks back more than the surrounding area.   It may look great leaving the repair shop, but long term it's no better and often worse than a decent repair in poly.

Rick who is your suppier?

Could some one lead me a supplier of finish grade catalyzed polyester. I can find tons of Gelcoats but little on finsh grade.

On the plus side for nitro is that it is easy to apply, wonderfully forgiving, and you can get good results with relatively inexpensive, simple spray and buffer equipment and some persistence. Like David Collins, I don't find some of the great old, worn nitro finished guitars unattractive, on the contrary. The sad part is that their finishes continue just to degrade and at some point they move beyond elegant and become... goners, not so elegant.

Many people feel that a shellac finish is not tough enough (at least not when it is relatively new) for a guitar that will be played with a pick and not cared for as perhaps is more common with classicals.

From what I have read about polyester finishes they require much finer tolerances and are more finicky than nitro, but it is what many if not most of the best pros use these days (I haven't found anyone who can do it for me up here, tho so I guess I'm stuck in my old ways).

_________________
Rian Gitar og Mandolin

[QUOTE=MichaelP] Could some one lead me a supplier of finish grade
catalyzed polyester. I can find tons of Gelcoats but little on finsh grade.[/
QUOTE]

Go to the McFadden
site.

Here is a
list of some other makers using their products.

They are a main supplier of polyurethane, polyester, uv cured, nitro, etc.

_________________
Eschew obfuscation, espouse elucidation.

Yep, McFadden.

Does McFadden sell the curing lights as well? Didn't see them on their site.

_________________
Dave Rector
Rector Guitars

Thanks

No, but I think all that has been oversold.   We finish about 30 instruments a month without UV, and it's no big deal.   The polyester is exactly the same with either UV or catalyzed with the exception that the light curing stuff has a UV initiator from CIBA Chemical in it whereas with the catalyzed, you mix in a cobalt drier and then MEKP. If you're doing fewer than about 50 instruments a month, I don't see a huge advantage to UV. We can rub out in 24 hours if need be, and 48 hours is more than adequate. The biggest advantage to the UV stuff is not the fast cure, but rather that you can load up a pressure pot with five gallons of the stuff and never have to mix chemicals.   

Thanks for clarifying that Rick!

For some reason I was only aware of the UV cure stuff and thought it would be a major investment to even try the stuff out. Not that I'm whipping out that many guitars a month anyway.   

_________________
Dave Rector
Rector Guitars

If some of you seasoned veterans of repair would be willing to address this question, I'd appreciate it:

When repairing scratches and dings, particularly on the soundboard, to what extent (or how often) do you find the damage affects the wood itself, not just the finish? What I'm getting at is trying to get a sense of how much the toughness of the finish really matters in the real world (I am assuming a very thin finish, as would be done on a fine handmade guitar, not a heavy factory armor). In other words, no matter how tough a finish is, if it's just a few mils of material over the soft spruce, does it really do much to stop the offending guitar pick or whatever from digging into the wood? Do you see a significant difference in how well a few mils of polyester or urethane actually prevent damage to the _wood_ as compared to nitro, or even shellac?



Thanks.

_________________
Todd Rose
Ithaca, NY

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

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

bumps and dings cat poly really cut down on those as well as pick scratches. That said I only know this from the factory guitars that come into my shop for fret dressing and other such repairs as I do not at this time use it on my builds.

As far as damage to the wood I look at it this way a cracked top is damaged wood. A small ding that depresses the wood is wear. From what I can tell Cat Poly really cut down on these. It has to be a trade off. the volatility and toxicity of the media, the associated cost of application, the damping effect vs. the durability it provides and the quickness of the cure.

i have put out some 50 guitars to clients with nitro, FP and waterborne finishes none have come back to me with damaged tops do to the lack of durability of the finish.

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Succinct! 

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Michael, thanks for your thoughts. I'll get back on later when I have more time to respond and clarify my question. Gotta go make dinner for my kids now.

_________________
Todd Rose
Ithaca, NY

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

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

Kevin Ryan uses UV polyester, and his finish spec is about 3 mil. You can't scratch one of his guitars with a pick, tried it. So, while you can dent any guitar top through pretty much any finish, a really hard finish like polyester is going to be able to take a pick scraping against it essentially forever without wearing through or scratching.

I'm going to be using the UV polyester because the cost of a UV light means less to me than the nastiness associated with using MEKP. There are a few companies out there selling them, but it's been my experience that they all overcharge like one would be disinclined to believe. They're the sort of thing a decent electronics guy can wire up for you a lot cheaper if you can find a decent deal on the bulb.

_________________
Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Bob, thanks for sharing your experience. That's helpful.

I am just beginning to gain experience in guitar repair, and haven't done any finish repair yet except for working on my own FP finishes, but my general observation has been that people can be surprisingly hard on guitars. Fretboard divots, deep belt buckle wounds, deep scratches/indentations from picks thrashing on the soundboard, etc...

My point is that, given how much force a lot of people put into the way they go at a guitar, the soft wood of a guitar top, in particular, seems like it may be vulnerable to attack regardless of the finish used - again, assuming the finish is just a few mils thick, as you would want it to be on a fine handmade guitar.

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...?

Obviously, it's a matter of degree - no finish is bullet proof. This is where my question to those with a lot of experience in repair of guitars with various finishes, or to those who've been doing polyester finishes and have observed the condition of their guitars over some period of time, comes in: do you find that it's a rare occurrence or a common occurrence that damage (or wear, if you want to call it that) delves into the spruce? Do you think that, for example, when a pick's attack on the soundboard has enough force behind it to drive an indentation into the spruce, a thin polyester finish does significantly more to stop that than a nitro finish?

_________________
Todd Rose
Ithaca, NY

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

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

I've never had an accident with MEKP; working with it is no big deal if you follow reasonable cautions. I use a medicine dropper for dispensing it into the polyester, I keep the containers closed, and it really doesn't take much to kick off the polyester...1 to 2 %.   I do suit up in a full Tyvek "bunny suit", I wear full glasses, I wear a properly rated respirator, and I work in an approved spray booth.   

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.

Experienced nitro guys I have worked with (Fred Latta, Addam Stark) seem to feel that poly is a lot less hazardous to work with than nitro.   For one thing, any gassing off is over in about six hours; in 24 hours you can't smell a thing. There is much less VOC use than with nitro.   

I don't agree that you can't scratch it, but it isn't easy, and guitars that I shot ten years ago still look great.   If the film is thin, it will move with the wood, so a ding that dents wood moves finish.   Adhesion can be amazing, too.

[QUOTE=Rick Turner]    

I don't agree that you can't scratch it, but it isn't easy, and guitars that I shot ten years ago still look great.   If the film is thin, it will move with the wood, so a ding that dents wood moves finish.   [/QUOTE]

Thanks, Rick. I appreciate your input, and understand the points you've made: that polyester is very scratch resistant; that it has held up extremely well on your guitars and kept them looking great; and that if the wood does get dented, the finish will move with the wood. That's all very helpful information.

I'd still like to know whether you think a polyester finish makes such dents in the wood less likely - i.e. whether the toughness of the polyester finish (even at just a few mils) provides significantly more protection against a ding or a heavy-handed pick scratch that indents the wood than a nitro finish does. Can you address that question?

I'm not trying to be contentious about this, or to doubt the wisdom of your choice of polyester. I'm just trying to put as many pieces of the puzzle together as I can, to make my own informed choices about guitar finishes.

Thanks.    

_________________
Todd Rose
Ithaca, NY

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

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