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How I approach a Nitrocellulose Lacquer Finish

Discussion in 'Finely Finished' started by Colt W. Knight, Jun 18, 2011.

  1. Colt W. Knight

    Colt W. Knight Doctor of Teleocity

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    Hello Everyone,

    Normally, I like to finish my projects before posting, but its tough keeping up with photos and posting all at once on a finishing thread because pictures all look the same. So you guys are going to get this real time.

    I am at a disadvantage because I am going to school at the moment, and I don't have access to all my wonderful tools and personal workshop. So I am just going to use the University's Ranch Workshop.


    There are a few essentials.
    1. Air Compressor
    2. Spray gun
    3. Lacquer, thinner, and sealer.

    My first stop was Sherwin Williams.

    [​IMG]

    God Bless Texas! Real Nitrocellulose lacquer and Vinyl Sealer for just 28$ a gallon.

    Then to Harbor Freight to grab a spray rig. ( HF because I am a broke college student, and HF is across the street fromt he Apt.)

    [​IMG]


    This traps and seperates moisture.

    [​IMG]

    This controls the air pressure entering the gun.

    [​IMG]

    This controls the air pressure going to the nozzle.

    [​IMG]

    This controls the width of the fan of the spray.

    [​IMG]

    This controls how much lacquer flows from the cup through the nozzle when spraying.

    [​IMG]

    This controls the orientation of the fan of the spray.

    [​IMG]

    Here it is all ready to go.

    [​IMG]
     
  2. Colt W. Knight

    Colt W. Knight Doctor of Teleocity

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    This is a new gun, so its going to get a good swishing and spraying of lacquer thinner to clean out the gun.

    [​IMG]

    I have used these 14$ purple guns before, and this newer model has several improvements in my opinion.

    1. It no longer has an O Ring sealing the cup to the gun. Solvent would melt and skew the old O Ring, and it would become oversized. It would then cut in half when screwing the cup onto the gun causing it to leak.
    2. The lid on the cup doesn't have a bunch of threads. Compare it to the lid on a 2 liter bottle of coke, and the lid on a gatorade bottle. This makes putting the lid on a much easier task. Once the cup deforms from the solvents, the multiple thread version was bad to cross thread.
    [​IMG]
     
  3. Colt W. Knight

    Colt W. Knight Doctor of Teleocity

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    I have used most sealers commonly used for nitrocellulose lacquer finishes, and some that aren't very common. By far, the best sealer for nitro in my opinion is vinyl. It provides 1) excellent adhesion to wood and lacquer, 2) cost effective because I use so little on a single guitar, 3) its tougher than most sealer, but still elastic enough to move with the wood and protect the lacquer.

    My favorite vinyl sealer is Sherwin Williams 24% Solids.

    [​IMG]

    The hardest thing about this 1 gallon paint cans is getting the lacquer/sealer from a full can. I spill too much if I try to pour it, so I ussually just dip it out and into a mason jar. Then label the mason jar. I don't have any down here in Texas, so I dipped it out and put it directly into the cup.

    [​IMG]

    This much vinyl sealer is more than enough to seal the guitar body and neck. However, this is a new gun, so I am going to spray a bunch into the air just adjusting the gun to spray like I like.

    As a side note. I was able to set the gun, and put two full coats of two-three passes each on the neck and body. So this 28$ can of sealer is enough to do how many guitars? I estimate around 20-25. I wish lacquer went that far!
     
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  5. Colt W. Knight

    Colt W. Knight Doctor of Teleocity

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    Here is the deal. A good finish starts with great prep work. An outstanding finish starts with even better prep work.

    Wood needs to be sanded through 220 grit with due dilligence and patience. You need to make sure you have all the low/high spots gone, and you have removed all sanding scratches. On some woods, like Pine, Ash, and Walnut, I highly recommend raising the grain with a damp cloth or denatured alcohol, and sanding the whiskers down. Once you have the body smooth as a babies behind, give it a good blast of air and wipe down with a naptha and a clean rag to remove any kind of dust, dirt, and grease/oil.

    [​IMG]
     
  6. Colt W. Knight

    Colt W. Knight Doctor of Teleocity

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    Okay, I sound like an idiot, but I tried to do a video illustrating the spraying process.

    1. You have to set your spray gun to spray according to your preference. Do this buy spraying a 2x4, a box, the legs on your work table, or whatever.

    2. When you spray, keep your gun square with work piece. Try not to bend and flex your wrist. Keep your wrist straight and move your arm. That way you can keep your spraying consistent.

    3. Do not start or stop spraying over the work piece. Start spraying in the air, and move over your work piece. Don't stop till you are spraying air.

    4. You want to move fast enough that you are getting a good even wet look, but not so slow as lacquer/sealer is building up, running, or starting too look like your looking into water.

    5. Overlap fan spray enough to keep an even coating/appearence.

    6. (1) pass is equal to the entire workpiece being evenly covered (1) time. (1) coat is equal to (2-3) passes. When you deal with lacquer products, 3 passes is generally about all you want to apply. Sometimes, you may want to wait 30 seconds or a few minutes between passes to make sure the lacquer isn't building up or getting too wet.



    If the lacquer/sealer looks like its hitting the body to dry, move your gun closer. Too wet, move your gun farther away.
     
  7. Stuco

    Stuco Poster Extraordinaire

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    Good idea for a thread, thanks for taking the time to do it.
     
  8. Colt W. Knight

    Colt W. Knight Doctor of Teleocity

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    Lacquer is an evaporative finish. It does not cure chemically like polyurethane. Essentially, it is just solids dissolved in solvents. So as the solvents evaporate, the solids become dry and hard. Lacquer takes so long to dry because solvents evaporate from the outside-in. This creates a hard outer shell the solvents must penetrate through to dry thoroughly.

    Because of this:
    1. Lacquer takes a while to dry, even though it seams like it dries quickly.
    2. Because the solvents flash off quickly, lacquer is dry to the touch almost immediately. Typically within 10-15 minutes.
    3. This makes lacquer a great choice for those of us working in dusty environments. Oil base finishes can take hours to dry, giving bugs, dust, and dirt hours to accumulate on your finish.
    4. Another benefit to quick drying time is that when we spray lacquer finishes, the lacquer will dry before it hits the floor of your shop or surrounding tools and tables. So you don't have overspray all over the place if you don't have a dedicated spraying location.

    Can you wet sand/buff lacquer when it becomes dry to the touch? Yes and No. If you try sanding and buffing immediately, it will be soft and scratch like hell. After a few days? Yes, it will buff up and look wonderful. Then in a few months, when it does dry, the solvents from the finish will have slighty raised the grain in the wood causing it to be slightly unlevel, and the finish will shrink. So you will get the appearence of a sunken finish. The grain texture will show through. You will still have a shiny guitar, but you wont have that wet glass super high gloss look.
     
  9. Colt W. Knight

    Colt W. Knight Doctor of Teleocity

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    I put two coats on this body.
    [​IMG]

    and two passes on this neck.

    Withough Sealer
    [​IMG]

    With Sealer
    [​IMG]


    The body gets block sanded with 320 grit. (220 would also be just find). The neck gets buffed with 000 steel wool.

    Note - Vinyl sealer isn't like a typical sanding sealer. You don't want to aggressively sand vinyl like sanding sealer or even shellac. Let the weight of the block do the work. If you get in a hurry/press to hard, the friction will warm up the vinyl, and it will roll up into balls and peel off the wood. Yes, you can sand vinyl, and it sand pretty easily.

    If I had my good spray gun, and large compressor with consistent air flow, I can spray vinyl smooth enough that I don't have to sand.
     
  10. Colt W. Knight

    Colt W. Knight Doctor of Teleocity

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    At this stage, would be an excellent oppurtunity to grain fill.

    Here is a how to, I did using solvent based grain filler.
    http://www.tdpri.com/forum/finely-finished/234759-just-another-grain-fill-thread.html

    I don't have my filler with me down here in Texas, so I am going to fill the grain on this guitar with vinyl sealer. So essentially, I am just going to spray, allow to dry, sand, and recoat till the process is done. Its a little time consuming, but it works well. Plus, I love the look of a sunken nitro finish over time. The guitar just looks and feels alive. Its a personal preference thing. If you like that pristine, wet glass look, its better to seal/fill in something like plastic (fullerplast) or polyester.

    Second Coating - Notice, in this light, you can see the pores of the wood. After the first coating/sanding, I used the air compressor to blow off all the dust and dirt, and gave it a quick wipe down with naptha.

    [​IMG]
     
  11. Colt W. Knight

    Colt W. Knight Doctor of Teleocity

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    Back to the neck.

    Maple is a closed pore wood, and doesn't require any grain filler. Walnut (skunk stripe) on the other hand isn't. It needs pore filler. Several ways to do this on a neck.
    1. Use pore filler
    2. Build up finish/sealer and sand flush.
    3. Use Cyanoacrylate glue.

    On flatsawn maple, I pore fill using CA glue before finishing. However, on figure maple, the CA glue can change the appearence of the figure under the finish. So you would have to CA glue the entire neck to get an even appearence. I think its better to just hit it with one coat of sealer, then apply the CA glue, and sand flush.

    [​IMG]

    [​IMG]
     
  12. Colt W. Knight

    Colt W. Knight Doctor of Teleocity

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    Thats all for today.

    When I used all the vinyl sealer in the cup, I give it a quick rinse and good swishing with lacquer thinner to clean out the gun.

    [​IMG]

    You can keep lacquer/sealer in the gun cup for a few a days, if you are continuously spraying. Just clean it up thoroughly when you are done. Sometimes a little build needs to be cleaned from the tip between sprayings.
     
  13. flanders7423

    flanders7423 Tele-Meister

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    Hey Colt, I can't believe you give all this knowledge away for free! I have learned sooo much good stuff from you.
    Seriously,
    Thanks
     
  14. Colt W. Knight

    Colt W. Knight Doctor of Teleocity

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    Thank you for the kind words.
     
  15. mgwhit

    mgwhit Tele-Holic

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    Colt, thanks for taking the time to do such a fantastic walk-through! Do you mind if I ask how you dispose of your waste lacquer and thinner? Newb question, but I'm not sure if it's too nasty to go down the drain or what. Thanks!
     
  16. Colt W. Knight

    Colt W. Knight Doctor of Teleocity

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    Well, if the gun has lacquer or sealer left in it, I pour it back into the can.

    When I clean the gun, I use about 2-3 ounces of thinner, and I spray that through the gun. So I don't really have anything to dispose of.
     
  17. Bluej58

    Bluej58 Tele-Holic

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    Very cool man , thanks.

    JD
     
  18. Phostenix

    Phostenix Tele-Afflicted

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    Dude! This stuff is invaluable. Thanks for taking the time to do it!
     
  19. scraggles

    scraggles TDPRI Member

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    That's the exact same gun I used for my build last week. Paired with a 40$ 3 gallon compressor and it did the job just as good as a 500$ rig. I don't really even need to sand but I'm going to just for a flawless mirror finish even though right now it's virtually perfect.
     
  20. ncteleguy

    ncteleguy TDPRI Member

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    Great thread, I have only completed one build that I finished with b/c, but after seeing this the next one will definatly be nitro! Thanks colt!
     
  21. Colt W. Knight

    Colt W. Knight Doctor of Teleocity

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    My nicer spray gun will really atomize the paint, and spray it on super smooth and even. It also holds adjustment very well. This inexpensive harbor freight gun works really well, but I can't seam to adjust it where the lacquer sprays and lays down like my more expensive gun. Plus I have to readjust the setting frequently.
     
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