Official Luthiers Forum!

Turbo411, a couple of things to remember if you decide to use KTM-9...
KTM-9 is a "water-white type of finish. In order to bring out the darker
tones and grain in the wood you will need to use some kind of sealer or
tint under the KTM-9. Epoxy has been recommened. I've been using
shelac as a under coat/sealer and I'm pretty happy with it. Also! blue
masking tape is VERY reactive with KTM-9! Even a few seconds of contact
and the finish becomes pitted.... The brown masking tape doesn't seem
to bother......

It's nice that the water based stuff won't blow-up and, it doesn't stink!
Either the KTM-9 dosn't have a smell or the nitro has ruined my sense of
smell?

Oh, Yeah, I'm new here, I missed being #1000 by 2   

longBob Long39013.8674189815

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"No man ever steps in the same river twice, for it's not the same river and he's not the same man.” -Heraclitus of Ephesus

[QUOTE=Todd Rose] It was interesting to me that the FWW article did not
include KTM-9 or Target products. I have zero experience with
waterborne finishes myself. I wonder, though, with all the various
manufacturers competing to produce good waterbase finishes these days,
if some of these might be as good or better than KTM-9 or Target, which
are the only two I ever hear guitar makers talk about. The FWW review of
the best products they tested was extremely positive in all regards --
durability, clarity, ease of application, etc.[/QUOTE]

Todd, I read that article as well and have been wondering the exact same
things. Perhaps a new thread ought to be started about it?

Mike

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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

Oh, and welcome, Jon and Bob!

Mike

_________________
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

Just a note of caution with KTM-9 or Target USL (Stew-Mac Colortone) ... If your gun has an aluminum cup, use disposable liners, a plastic or SS cup, or a teflon-lined cup. These finishes can react with the metal and cause granualtion in the liquid. It doesn't happen consistently, but it's a mess when it does.

You can get 1qt. disposable liners and nylon replacement cups at Jeff Jewitt's site:

http://www.homesteadfinishing.com/index.html

I think you can get 600ml gravity-cup liners here, but you may have to call them (I can't find them on their site anymore): http://www.spraygunworld.com/

BTW, I met and talked with Jeff Weiss, the owner of Target Coatings, at the Atlanta IWF show in August. Word is he's working on a further improved version of USL specifically for the stringed-instrument trade, to be sold only through Stew-Mac. Release date ????

I like and use USL over Z-Poxy, when I'm not FP'ing.

Best,

Jim

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James Warwick
J. Warwick Guitars, LLC
http://www.jwarwickguitars.com

Some reflections on finishing:

I have probably made every mistake possible in learning how to use waterbased lacquer, and have tried probably every product available except KTM9.

I have found there is a balance between spraying on enough to wet the layer underneath the current coat, and getting too much on.

Not getting enough to wet the previous coat shows up with
tiny, white sanding marks below the surface of the new layer. Don't despair if this happens, because repeated soaking of the surface with Everclear on a paper towel will cause them to disappear as it helps the layers to burn in.    

Too much causes blushing, which can be white or blue or purple. On lower layers, the white will clear with drying, but not in the top layers. Refinish time.

I've found the best is Target Ultima, which I assume is the same as StewMac's USL. Target's product five years ago left many air bubbles, but the new one is great. They claim it is harder than nitro, I couldn't say. But what is different from others is that there is a much greater range between too little and too much, so that I can apply two coats in one spraying to fill in the light areas between the first passes, etc. I've even done three coats, but it is risky. My working guitar has a translucent purple glow to the dark mahogany back and sides. I got greedy. But I've got two others finished that are gorgeous, with no purple or blue whatsoever.

I use Zinsser's seal coat shellac to seal the wood and give it the wet look, and have found it safer to put any tint in this layer, rather than in the lacquer. It's less likely to be sanded into later. However, repeated coats of shellac to get the color even, or add a translucent sunburst, leaves a rough surface (don't dare sand it) and the first coat of lacquer needs to be diluted at least 25% with distilled water to properly wet the shellac. I also dilute all coats 10%. Rolfe Gerhardt told me this tip in a phone call. It seems to level easier.

I buy from Target directly (800-752-9922) where I also bought a Sata minijet spray gun, which I love. About $235 delivered.

Target also sells a waterbased shellac, which I found to not adhere too well due to less penetration than normal shellac. However, that quality makes it excellent for sealing end grains of top wood (allow for slight end grain swelling) before using thin super glue on bindings or rosettes. Vinyl sealer has toxic nitro fumes. Slop it over onto the top to keep the glue out of it, too--it sands off quickly.

One last finishing experience I'll relate is that Dynabrade makes something called a finishing sander (air powered). Model 57920 has clips on the pad unit, allowing one to use any sandpapar. On the last guitar I finished, I used 800 grit automotive black sandpaper directly over the last spray coat, then 1500, then 2000. I used minimal water to keep the area wet, but no runs--they burn in quickly. I use a blue scrub sponge to wipe up and a paper towel to dry for a good look. The scrub part of the sponge quickly removes any buildup on the sandpaper while running the sander.

Subsequent buffing went three times as fast as when I carefully sand by hand, as there were no fine tiny scratches that take forever to remove. Of course, I got some of these in the waist and cutaway, where I couldn't use the sander, using the same grits by hand. Finally, a tool that really works!

Scott

Scott the white sanding spot you refer to is sanding dust left in minute sketches. the way to eliminate them is first to clean the surface well before spraying again and spray a light coat of DA on the surface and allow to flash off this will melt the solids in the sanding dust an allow them to cross-link with the next coat I do this after every sanding session. and if it has been more than 4 hour since the last coat to get the best possible cross-link between the previous coat and a new coat.

Michael, Thanks for the tip on DA. Jeff Weiss told me that I could spray Ultima over old nitro if I rubbed it down with DA first, which I did with seemingly very good results. Don't know if it will peel off someday, but a year and a half later, the finish is still clear and intact.

The white sanding spot in question won't occur if the surface is sufficiently wetted in the next coat's spraying, as the dust is dissolved, which I think is also necessary for good adhesion and burning in, because the dry surface is also dissolving. Ergo, white spots will tell you that you are not spraying on enough. However, I like the idea of opening up the surface with DA if it's been over four hours since the last coat.

My understanding is that DA is just ethanol (Everclear) plus an additive that makes it impossible to drink. In answer to another question I saw on this forum, R. E. Brune, in a lecture at the 2001 GAL convention, said one should never use any alcohol to mix shellac that cannot be drunk--presumably because you are still consuming
it by breathing the fumes.

Scott

You are right about the spots but what I was assuming was that the dust was trapped in the sanding scratches and that the finish could be bridging, therefore not emulsifying the dust. The DA will penetrate the scratch and insure that the dust is emulsified with the next coat.

Yeah Bug Poo!!

_________________
John Lewis
Wannabe builder owned by 2 crazy dachshunds