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Quick question about spraying Nitro
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=39474		 Page 1 of 1
Author:  Rob Flindall [ Sat Feb 23, 2013 10:12 pm ]
Post subject:  Quick question about spraying Nitro
Hi guys - I have a quick Nitro question.

Yesterday I sprayed the first 2 build coats of Nitro on my two guitar builds. I wasn't able to get to spraying more coats tonight, but I plan to do two more coats tomorrow. Do I need to worry about anything having left it two days between successive coats? Do I need to sand?

Thanks guys - can't wait to get back at spraying!

Rob
Author:  Chris Pile [ Sun Feb 24, 2013 12:47 am ]
Post subject:  Re: Quick question about spraying Nitro
I usually just scuffed it every few coats with fine scotchbrite.
Hit it with a tack cloth, and you're ready to shoot again!
Author:  theguitarwhisperer [ Sun Feb 24, 2013 1:57 am ]
Post subject:  Re: Quick question about spraying Nitro
I sand the first time after 4 coats, with 400 grit. It only takes a few coats after that then I level with 1000 before final buffing.
Author:  npalen [ Sun Feb 24, 2013 1:03 pm ]
Post subject:  Re: Quick question about spraying Nitro
I level sand with 220 prior to spraying color with aniline dye in alcohol. Then level sand again after a half dozen coats of clear nitro prior to final clear coats. Then, after a month of curing, P1500 and P2000 before buffing with medium and fine Menzerna.
I used to use tack cloths but have found that wiping down with naptha and then blowing clean with compressed air works better for me. Everyone who has been building for a while develops their favorite techniques. With that said, you CAN teach an old dog new tricks, he just won't remember them tomorrow. bliss
Author:  Rob Flindall [ Sun Feb 24, 2013 7:00 pm ]
Post subject:  Re: Quick question about spraying Nitro
Thanks for the help guys. I was mostly concerned whether or not there would be proper adhesion and whether or not leaving the spraying for a couple of days would create witness lines in the lacquer. But you've answered all my concerns. Tomorrow morning I forge ahead with 3 more coats of lacquer!

I'll tell you one thing that I'm impressed with nitro though. I sprayed my first guitar I built with water based lacquer. I wasn't too impressed with it. You could still put a fingernail mark in the lacquer a month after spraying. This nitro is a completely different beast. These first two coats are already hard as a rock. I love it. I can't wait to finish spraying, wait for about 3 weeks and then buff these babies up! bliss

Rob
Author:  Rob Flindall [ Tue Feb 26, 2013 9:41 am ]
Post subject:  Re: Quick question about spraying Nitro
Ok, I have another question as my spraying continues. My first two coats of nitro went on with a fair bit of orange peel before I was able to dial my gun in and thin my lacquer out properly. The next three coats went on nicely, but a bit of the orange peel is still showing through from the first coats. My last coat of three went on at 7pm last night. (So, I have 5 coats in total on the guitar so far) I was wondering if it was ok to wet sand the guitar now to do some levelling before I hit it with another 3 coats later today? And if so, what are your suggestions for grit at this stage?

Rob
Author:  Chuck Gilbert [ Tue Feb 26, 2013 10:42 am ]
Post subject:  Re: Quick question about spraying Nitro
I wouldn't wet sand simply because it's more trouble than dry sanding with 320 or 400 grit between coats. I get everything nice and level and then spray a couple of "flash" coats at the very end with a 2:1 lacquer to thinner mix adding a little retarder to allow better flow out. Those are the coats I try my best to make smooth with little orange peel, but in the end orange peel just makes final rubout harder to do. I get the same final polish whether I'm really smooth on the final coats or not.

Good luck,
Chuck
Author:  B. Howard [ Tue Feb 26, 2013 2:07 pm ]
Post subject:  Re: Quick question about spraying Nitro
You are going to need to sand before you buff at the end anyway.....so why sand twice? Actually more work and time to do it twice. Get enough build on it, let it cure and then sand once and buff. Most folks sand to much and add too much reducer to their rts.
Author:  Jeffrey L. Suits [ Tue Feb 26, 2013 2:41 pm ]
Post subject:  Re: Quick question about spraying Nitro
http://www.eagleabrasives.com/

Thanks to Brian Burns, for turning me onto Buflex several years ago.
Author:  Rob Flindall [ Tue Feb 26, 2013 4:19 pm ]
Post subject:  Re: Quick question about spraying Nitro
Ok, so here we are after the 6th coat. I'm laying out the lacquer at 5mils wet, but it drys with a bit of orange peel. I'm guessing that's because my first two coats weren't the greatest and had a fair bit of orange peel. Comments?

Oh - and another question. I'm on coat 6 and I've gone thru about 1 1/3 quarts of lacquer. That seem about right?

Image

Image
Author:  Greg B [ Tue Feb 26, 2013 4:32 pm ]
Post subject:  Re: Quick question about spraying Nitro
It doesn't look bad. You'll get it on smoother with experience. Don't worry about adhesion or witness lines. It's not an issue.

I'd suggest putting on another 2-3 thin coats, and then knocking it back about 50%, staying away from edges completely. After another 3, sand to 95% level, then spray the last couple thin coats.

EDIT: by "knocking it back about 50%" I mean sand it until about half the orange peel is flat, not sanded until half the finish is gone...
Author:  Fred Tellier [ Tue Feb 26, 2013 4:44 pm ]
Post subject:  Re: Quick question about spraying Nitro
Quote:
I've gone thru about 1 1/3 quarts of lacquer. That seem about right?


I do a complete guitar with less than 1 quart with a HVLP conversion gun, about 1/2" left in bottom of the can. I used to use the whole quart plus about 1" out of the next can when I used a conventional gun, more overspray and bounce back at the higher pressure. It looks like you are spraying heavier coats than I do so you night have enough on already, pull a bit of the fingerboard masking to measure your coating thickness, should be a couple thousands of an inch thicker than the finished thickness after leveling and buffing.

Fred
Author:  Rob Flindall [ Tue Feb 26, 2013 8:50 pm ]
Post subject:  Re: Quick question about spraying Nitro
Thanks for the responses guys.

Fred - The 1 1/3 quarts of lacquer is for two guitars. I've built a wenge and a bubinga. Given your usage details, I think I'm on track? I was thinking 2 more coats. I'll definitely take a peek at the finish thickness though by pulling away the tape on the fretboard though.

Greg - Dependent on my finish thickness (see above) I think I'll do exactly as you say. Sand it back a bit and then hit it with 2 more coats. I'm enjoying this process but I'm also nervous as hell spraying the guitar. I'll be a nervous wreck when I use my buffing wheels for the first time! lol

Rob
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