Tiny White Dots in Nitrocellulose Finish?

Discussion in 'Finely Finished' started by tkmclaughlin, Oct 16, 2019.

  1. tkmclaughlin

    tkmclaughlin TDPRI Member

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    In the course of wet sanding through the grits and ultimately buffing a guitar neck, I noticed what look like tiny white specks in the finish. It's on the spot right above where the nut would go on the headstock. (see photo)

    Some are opaque white and some appear a little more translucent. I think these are air bubbles that were in the finish which filled with powderized nitro dust as I sanded through the grits and then got permanently embedded in the finish. Am I right? If so, where did I go wrong? Did I not let the finish cure long enough?

    Am I correct that the only way to correct them is to sand the finish back down until the dots disappear and (depending on how far down I sand) either respray some new layers or try to buff out again?

    (EDIT - I still have to apply the decal and then bury it in lacquer anyway, so I guess the right move is to gently keep sanding until those dots disappear and then take care of it all when I deal with the decal...)
     

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  2. eallen

    eallen Tele-Afflicted

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    You are on target on the bubbles. The question is why were they there to begin with. The most often seem to show up when a person puts the lacquer coats on too thick and the previous coat isn't done gassing off before the next coat. Wahala, gas get trapped causing bubbles.

    Another option can be people putting their nitro job out in the sun or under a heat lamp to dry faster. The result is the outer surface hardens before the gases again can evaporate out trapping them.

    Any of these fit? Heavy coats? Sun or under heat to dry?

    Yes, sand until they disappear and layer with light coats as you do your decal.

    Enjoy

    Eric
     
  3. tkmclaughlin

    tkmclaughlin TDPRI Member

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    Too heavy coats. Guilty as charged! I’m always in such a hurry to get the coats to build up.
     
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  4. Gipper

    Gipper Tele-Meister

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    I hear ya brother! I avoid finish work as much as possible.for a multitude of reasons, but #1 is I am a perfectionist with no patience. And when it comes to spraying finishes that is bad juju!
     
  5. dogmeat

    dogmeat Tele-Afflicted

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    eallen is dead on
     
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  6. eallen

    eallen Tele-Afflicted

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    Most of people's dilemma with waiting forever for nitro to dry enough to buff is they put it on to thick. Use multiple light coats of 3 passes per coat. If it takes more than a little bit to bit be tacky it is too heavy. So the last 2-3 coats as gloss coats to smooth things out. You will be surprised how quickly it passes the fingernail test in a cavity to be ready to buff.

    Rinse, repeat, enjoy.

    Eric
     
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  7. Vizcaster

    Vizcaster Poster Extraordinaire

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    I wouldn't expect nitro sanding dust to get caught in the bubbles, but buffing compound certainly would. Or the bubbles are white to begin with. If its from your polishing medium, see if you can remove the white residue of compound with naphtha, but sanding further will serve to level it out so long as you don't burn through the areas around it (especially the upper edge of the fingerboard where it transitions back to the headstock face). I'd be tempted to clean out the bubbles as best you can (which will also remove any wax from the buffing) and drop fill either with nitro or with medium CA glue, let it dry and try to level it out. Then you can come back with a spray topcoat when you bury the decal.
     
  8. Silverface

    Silverface Poster Extraordinaire Ad Free Member

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    Unless it is a two-component lacquer it does not "cure. Conventional lacquer dries ONLY by evaporation, and properly applied coats dry in 30-60 minutes in most cases. I rarely wait more than aa day to buff - usually the afternoon after I finish clear coats (I do not "finish sand". It's a repair procedure that should not be necessary if application was done correctly.)

    Common products that are exceptions to the 30-60 minute dry time are Deft and Colortone, which are "lacquer enamels" containing naphtha as a solvent. If you see that on the MSDS it's gong to be a slow dry material! But it STILL doesn't "cure"!

    ^^^^^THIS!

    Color coats should all be transparent, and start to cover and flow at the 2nd to 3rd coat. One coat - 3 passes - should be "see though". Lacquer IS NOT APPLIED LIKE ENAMEL PAINT!

    The white deposits on the neck look like wet sanding residue not cleaned off.

    Did you sand *at all* between coats? If so - DON'T! This is what it causes - surface contamination.

    Without having the neck in hand to look at with an electronic microscope and/or do some tests on it's virtually impossible to be sure. If it doesn't sand off with 1500 it's embedded in the coating. Your call - sand it all off and recoat, spot sand and pray you can match the color, or live with it.
     
  9. torodurham

    torodurham Tele-Meister

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    Do you use mineral spirits to wet sand with?
    If so..dried residue is white. Ya gotta make sure ya remove it from pits or low spots in lacquer.
     
  10. ponce

    ponce Tele-Holic

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    Good quality thinner can speed up the process.
     
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  11. Peegoo

    Peegoo Tele-Meister

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    If the surface is level-sanded, you can stop right there. Use an old, soft-bristled toothbrush (dry) and scrub the area. The bristles will knock the dust out. Use compressed air to clean the area. And when you hit it again with clear, things will level out and the white spots will go away. Many light coats is a lot better than fewer thick coats.
     
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