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First Timer: Question on Nitro Spray Can Finishing

Discussion in 'Finely Finished' started by Zaden, Jul 12, 2018.

  1. Zaden

    Zaden TDPRI Member

    18
    Aug 13, 2010
    UK
    Hi all,

    As the title implies, I am undertaking my first build and have begun the process of finishing the body. I am going for a solid colour nitro finish from a spray can.

    My question is as simple as this; should the body feel somewhat rough after spraying the body with a number of coats of white primer?

    I sanded the filler/sealer back to the point where it was beautifully smooth, however after spraying the white primer the body is somewhat rough to touch again. I have sanded back but should I expect to need to do this with my colour finish too?

    Cheers
     
  2. It depends on what you mean by rough. Primer is not meant to be a glossy smooth finish so it wont feel smooth like glass. It is more on how does it look? Does it look orange pealed or flat? If it is orange pealed then it is your spray technique.

    Also, it is generally not a good idea to touch your finish between coats unless you are sanding. If you do, you need to wipe it down with naphtha before your next coat to remove any residue from your skin that could cause adhesion problems with your next layer.

    Pics are always helpful.

    Great to see you jumping in!

    Eric
     
    Last edited: Jul 12, 2018
    Toadtele likes this.
  3. pedro58

    pedro58 TDPRI Member

    48
    Jan 25, 2004
    North Texas
    What are you using as a primer? Shellac? If it's sandpaper rough, you'll need to sand it flat like your filler coat was. If you sand through, respray. It's a pain in the neck.
     
  4. adjason

    adjason Friend of Leo's Silver Supporter

    Jan 9, 2010
    virginia
    Yes it feels rough when I spray something like BIN primer- sand it smooth and repeat a couple of times before nitroing it
     
  5. Vizcaster

    Vizcaster Friend of Leo's

    Sep 15, 2007
    Glen Head, NY
    Is it possible you're getting overspray or bounceback? If you have perfect-storm conditions (hot, no air circulation, atomization hard to control with spray-bomb cans) it's possible for the mist particles hang in the air long enough to dry, then settle on the work without melting in, leaving a rough finish. When that happens you'd need to smooth it out before the next coat - an old timers trick is to use brown craft paper (remember grocery store bags that were paper?) instead of sand paper for smoothing out overspray.
     
  6. Silverface

    Silverface Poster Extraordinaire Ad Free Member

    Age:
    66
    Mar 2, 2003
    Lawndale CA
    Yes, but not after sanding.

    However, I'm more concerned about your question left unasked -

    What are you applying AFTER the primer; how are you applying it; what are you expecting to do between coats?

    If lacquer your "coats" are made up of multiple light passes and finished with clear coats where only the final one or two are "flood coats; there is NO sanding between lacquer coats (except for fixing tiny runs) and if much sanding appears to be needed after final; clear application something is wrong with the application technique. Light sanding with no rougher than 1500 maybe, but straight to buffing is what *should* be the result.

    You should already know this and be working out all the products and techniques on scrap wood - everything from prep to polishing - before applying a drop to the actual guitar part. It's generally a bad (and costly ) idea to learn on the actual guitar.

    Have you read all the material on Reranch.com? That's a good place to start.
     
  7. Zaden

    Zaden TDPRI Member

    18
    Aug 13, 2010
    UK
    Hi Silverface.

    I have indeed through re-ranch, along which watching copious amounts of youtube tutorials. The outline of my intentions from here out would be as such;
    1. -a final coat of primer with potential light sanding until smooth. A final coat is need as sanding has taken be back to the wood on the edge of the body.
    2. Light coats of colour from a nitro spray can until one or two coats over what looks complete to the eye. I then understand some wet-sanding may be needed?
    3. Finish it off with 2-3 coats of clear finish
    You mention a "flood coat", I assume this is a wetter application on the final coat or two?

    Thanks,
    Z
     
  8. Buttered Biskit

    Buttered Biskit TDPRI Member

    Age:
    37
    61
    Sep 23, 2018
    Barton, WI
    You should never sand you final coat of color. Really any color coats. You rin the risk of the sand scratches swelling and showing through the clear. Just get good coverage and dont worry too much about roughness. Worry about the texture (orange peel), that will show through the clear.
     
  9. mgreene

    mgreene Tele-Holic

    777
    Jan 27, 2010
    south carolina
    I have scotch-brighted color coats - especially when they are meant to be mat or semi mat. In fact, in my last build, which was mean to look like an oxidized mint paint job, the final finish was a scotch brite rub.

    Car guys sand color coats so I am interested in hearing about not sanding color coats as a thing.

    How do you solve runs? (Aside from not making one in the first place :p - which can be hard to do with a rattle can.
     
  10. Silverface

    Silverface Poster Extraordinaire Ad Free Member

    Age:
    66
    Mar 2, 2003
    Lawndale CA
    Do NOT sand the color coats when clear is to me applied. Lacquers melt into each other creating ONE coat, and sanding helps with nothing and may introduce contaminants. There's no logical or technical reason to sand between color and clear. Even fixing runs at this point can create appearance problems, so there should be enough practice applications of ALL coats to avoid this.

    2-3 coats of clear is awfully thin. If you have practiced this and can get a glassy-smoothi finish with 6-9 light passes (2-3 "coats") then it may look fine initially - but it will provide very little surface protection to the color, and it may be incredibly easy to buff straight through it. When emulating vintage finishes I apply 3-6 clear coats; at other times, especially with highlighted grain and 3-dimensional looking "pop", 5-8 coats is about the minimum I work with.

    Most first timers need quite a few more coats applied using almost invisible "passes" for consistency.

    Yes, a "flood coat" is a wet-look coat applied in one pass - two at most. There's no way around practice applications over complete systems to get this right, or it will have runs, a "wavy" look and other issues. But without it you end up having to sand far too much, an the gloss rarely ends up as high as when it's done correctly.

    Again - practice on scrap - with everything from prep to sealer, primers, toners, dyes, colors, clears and don't try buffing until your application technique is refined enough to eliminate wet sanding, or at worst, 15-20 minutes starting with 1500 grit - nothing more coarse.

    Just to clarify - that's without clear coats, correct? Because no matter what the sheen of final clear coats color coats should never be rubbed, sanded - only tiny spots to remove runs. knocking down the gloss of a color coat has no effect on the gloss of the clear coats.

    In most cases it's a good idea to apply clear coats over ALL lacquer color coats, even if the final finish is to be satin. color coats are more easily stained/discolored and if physically damaged they are much harder to repair.
     
  11. mgreene

    mgreene Tele-Holic

    777
    Jan 27, 2010
    south carolina
    On my last build I did a light sanding of the color coat and then scotch brited the clear coat.

    [​IMG]
    On the guitar in my avatar, I had some sags in the clear coat and a run that I didnt see in the color coat (until I had started to clear it). I came back and sanded it flat with 800 and recleared and a final buff with compound. Didnt hurt anything. I just did whatever worked.
     
  12. Silverface

    Silverface Poster Extraordinaire Ad Free Member

    Age:
    66
    Mar 2, 2003
    Lawndale CA
    Hey, sometimes sanding the color coat works fine, and "whatever works" is where some of the most creative finishes are created - but not usually by intent. But it's completely wasted effort unless fixing small runs.

    Here are few notes that may help some of you on future projects -

    There's no reason to sand the color coats, because the clear (if applied properly) melts in and self-levels. There's more danger of rubbing-in an airborne contaminant (or one from the soaking water) or creating a tiny scratch embedded with something (that shows under some lighting conditions) than there is any possible benefit. Even when it doesn't hurt anything it's wasted effort, because it doesn't *do* anything.

    Some sand color coats because they think the color coat is too rough or wavy looking. But sanding isn't the "fix" for that problem - correcting and refining the application technique is, because those things are only caused by application errors.

    Which goes back to what a bunch of us preach - do practice applications of COMPLETE systems on scrap until you can consistently do it right - THEN start on the guitar part(s). It nearly always gets you better results, prevents serious errors on expensive bodies or necks, helps you learn how to fix errors that DO happen, and virtually eliminates threads that start with "Help! I think I screwed up my guitar!" :D

    Using 3m pads on clear coats is a great way to get a satin effect, even with gloss lacquer. It's also a good way to knock down the gloss if a satin clear was "burnished" to a higher gloss by using retail car polish (instead of the right stick or clay buffing compounds) or simply overdoing buffing with very fine compound.

    When you sanded through the clear to fix a color run you did the right thing. The biggest mistakes I see in that type of situation is sanding the clear, the run and either 1)sanding through the color and applying more color...and then clear, or 2) sanding the clear, fixing the run but applying a little more color as "insurance - and then re-doing the clear.

    In both cases there's at least one area where some of the added color coat is "floating" in clear around the edges. Depending on the color it either looks like a different color; or like a high-altitude "cloud"; or (more rarely) pigment separation occurs and a transparent white "lacey fringe" appears in certain lighting conditions. And bummer - there's no fix other than stripping and starting over or applying enough color over the whole thing to hide the problem(s) and clear coat again.

    Actually, that last one is how Fender used to fix finish errors not noticed until it was too late - there are dozens of examples of custom colors applied over screwed-up sunbursts!

    I've spent years testing all sorts of coatings, intentionally causing failures, tried to do things very wrong and still try to "save" it, used incompatible products over each other, mixed lacquers and all kinds of paints together, used them and tested the results...

    ...and it's amazing how lucky you can get and how many wrong or weird things will end up looking good and lasting for years. But none of that happens very often.


    Rule #1, though, that should be followed exactly, is use proper safety precautions - and #2 is have fun. EVERYTHING else is optional.
     
    mgreene and eallen like this.
  13. I'm a big fan of Silverface's 2 rules, safety and have fun! When you quit doing that there is no sense doing it. Every mistake is a great opportunity to have fun learning.

    Great work. Keep it up and show some more!

    Eric
     
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