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Admittedly not one who is super experienced with finishes but mostly do an ok job on past builds.

Current build called for a black top over Sitka.

My process:

Sanded top progressively to final 280 grit.
Sealed rosette with shellac.
Masked off rosette.
Tinted top with Trans Tint Black.
Waited 24 hours and re-stained.
Waited 24 hours and the sprayed initial build layer of KTM-9 tinted with Trans Tint Black.
Waited 24 hours and leveled with 3m 500 grit wetted with tap water.
Wiped with Everclear and sprayed clear KTM-9.
Waited 24 hours and wet sanded again.
Wiped with Everclear, removed masking from Rosette, reshot with KTM-9.
Waited another day, sanded lightly and began light coats of KTM-9 with a quick blast of Everclear for adhesion.
This is where the trouble developed.......Fisheyes.

The long and the shorts is I could not rectify so I re-sanded to bare wood.
I switched from my compressor (thinking oil contamination) to oil-less turbine driven air (think warm and dry air). Plus a new air hose.
Tried the above process again but still having fisheye problems.

BTW, I clean the gun meticulously with warm water and then with Everclear between each session, whether over night or just an hours wait.

I'm now pretty much at my wits end and hope you guys/gals will chime in and see anything obvious that I'm missing or provide recommendations.

Thanks,
Tom

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(alias: gasawdust)

wow. All I can say is that looks like a lot of work. Haven't used that stuff yet. I feel for you.

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"Preoccupation with an effect gives it power and enhances the error"
from "Your Owner's Manual" by Burt Hotchkiss.

Are you using stereated sandpaper? I believe you need aluminum oxide papers for waterbased finishes. But you're gonna want to dig around a bit to confirm that, I am most definitely not an expert...

Nope, not sterated. 3m wet or dry used wet with water for lubrication and flushing of particles.

One person told me that possibly my coats were too heavy (no sags or runs though). Don't see that this would be a contributor but something surely is causing it.

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(alias: gasawdust)

Tom,

Sorry to hear you're having problems. One question comes to mind. What are you mixing your TransTint with.....alcohol or water?

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Jimmy Caldwell
http://www.caldwellguitars.com

When applied as stain I used straight from bottle to to clean cotton rag to bare wood.
When blended with KTM-9 I gave it about 1/2 oz Everclear for 6 oz. KTM and about 1/2 oz Transtint.

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(alias: gasawdust)

Disclaimer: I don't have experience with waterborne finishes, but do have alot of finishing experience.



When you stripped, and started finishing again when did the fisheyes develop? At the same point during the process, or earlier?

Before finishing, after final sanding I wipe the body (or whatever part I'm finishing) down with naphtha, let it dry, the wipe it down with ammonia. A cabinet builder/finisher told me to do this years ago. I've only had problems with fisheyes once, and it was on a neck re finish. The owner had used fingerease for 10 years. I stripped it, doubled up on the naphtha and ammonia, and no longer had problems.

Sometimes trapped solvent bubbles will look like fisheyes. If the fisheyes are happening later during the process it could be that you're not waiting long enough between coats. Manufacturers recommend times are usually minimum times, based on perfect drying conditions. It's common to have to extend wait times between coats over the recommend times with most finishes.

I also recommend an inline air filter like the one at the top of this page. http://www.tcpglobal.com/spraygundepot/itemdetail.aspx?itemno=DEV+HAF-507
I doubt that's your problem, but it can't hurt. I'd also recommend wiping it down with naphtha instead of everclear before re coating. (I'm assuming naphtha won't hurt the waterborne finish, test on scrap) Alcohol won't cut grease. Naphtha is a better de greaser. I suppose oils from your skin could cause problems. Be sure and let the naphtha dry.

Again, I don't use waterborne finishes, so some of my succestions may not work with them. If someone with actual KTM 9 experience says I'm full of mud, believe them.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

Fisheyes aside, I'm concerned that you're using too fine a sandpaper between coats. You want to be using 320 at the most between coats because its' a mechanical bond. As for the fisheyes are you using at least an inline water/oil filter? And if so, when was the last time you replaced it? What are you sanding on and could it be contaminated? Did you wash your hands before sanding?

Sanding your first day's coats, use 320 and a felt block -- you're not trying to get it flat, you're trying to scratch it for the next round. Use a grey scrubbie to scratch binding edges and the soundhole. Blow off the dust thoroughly and hit it with a tack rag. Then do the alcohol wipe to aid burn in. After your second day of spraying get more aggressive about leveling.

Woody, the naptha is fine before applying finish, but it actually has some oil residue, so while its good for cutting oily contamination, I'd follow it up with denatured alcohol. He needs the alcohol to get the KTM-9 to melt together into the succeeding coats -- it's not a perfect system, but helps minimize witness lines.

Thanks guys.

Woody - I was about 7-8 coats of clear over the tinted before the eyes cropped up. Using Mike Doolin's guidelines I was spraying quick light coats with an hours wait time in between. One thought is maybe the eyes were just out-gassing of the previous coats. I'll allow more time in between spray sessions and see how that goes. Temps have been in the high 70's here so I've been letting the box dry outside in between sessions.


The turbine I'm using is oil-less. It's marginally sufficient to drive my Awata gun with thinned ktm viscosity so I'll stick to it and discontinue using my compressor.

I haven't used ammonia but will test it on some scraps with ktm to see if compatible.


Dave - I thought the alcohol wipe down was to help facilitate chemical bonding of old/new ktm. I can see your point on 320 vs. 500 grit if I was relying strictly on a mechanical bond. That said, I appreciate the advice and will defer to your expertise. I have felt blocks but was using a cork block this time around. It's only been used on bare wood and ktm.

Wash my hands....hmm...no.

The Turbinaire turbine is hot, dry, oil-less air. Quite confident that is not the problem and the hose is brand new, never used on my compressor.

I'm pretty tapped out on how the contaminant got on the surface but obviously something is causing it.

I'll keep on plugging along and see where this takes me.

Thanks,
Tom

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(alias: gasawdust)

Tom,

I reread your original schedule and found something I'd overlooked..... Tap water. There's something contaminating your finish and everything else on your schedule looks good. David mentioned the use of gloves and an inline filter, and stearates have also been mentioned, so I'm just trying to eliminate possibilities. Depending on where you live, tap water is another possibility. I do have quite a bit of experience with waterbournes and when I was using water as a lubricating agent, I always used distilled water for fear of just the problem you're having. I've since switched to an eco-friendly mineral spirit and have had great results with that also.

Obviously, it's difficult to identify these types of things, but eliminating identifiable possibilities is one way to approach it.

Good luck.

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Jimmy Caldwell
http://www.caldwellguitars.com

Tom, the alcohol wiping was something that Mike Doolin figured out. On new finishes, it helps the lacquer melt into the preceding days coats, thereby making a unitary film, or at least close to it. In the case of repairs, the denatured alcohol helps do the same for older finishes, softening up the top coat and allowing the repair coats to melt in, albeit not nearly as well as it does on new finishes. As for the sandpaper, I just looked at Mikes KTM-9 page, and you are right that he was using a finer grade. It's been a while since I sprayed waterborne.

Friends don't let friends use waterborne....

Are you spraying finish in direct sunlight?

When you say "fisheye", what exactly do you mean by that?

Not direct ...fluorescent in my shop.

Fisheye is where the finish is repelled forming small circles i.e. fisheye.

_________________
(alias: gasawdust)

I'm surprised nobody has mentioned the possibility of silicon being a problem. If you've recently sprayed any around or waxed something, like on a tablesaw top, stop looking elsewhere. That stuff stays around for months just waiting to sneak into your finishing room and make fisheyes.