Sanding Sealer for Spray Enamel?

Discussion in 'Finely Finished' started by scottythered, Oct 11, 2011.

  1. scottythered

    scottythered TDPRI Member

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    I'm going to color a kit guitar using Rust-Oleum's Painters Touch primer & spray paint, along with the concordant Rust-Oleum PT satin finish.

    My question is, when I select a sanding seal for underneath the primer, does it make a difference which kind I use? All things considered, is there a type to avoid, because it won't play well with my top coats? :confused:
     
  2. Colt W. Knight

    Colt W. Knight Doctor of Teleocity Ad Free Member

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    Avoid lacquer based products. Lacquer and enamel don't play well together.

    I have used minwax poly sanding sealer under enamel with good results
     
  3. scottythered

    scottythered TDPRI Member

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    Very helpful, thanks! :D
     
  4. lumberjim

    lumberjim TDPRI Member

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    I didn't think to check before I painted, but I used StewMac's nitro sanding sealer, let it cure 5 days and sprayed enamel today. This is cropping up :

    [​IMG]

    I'm thinking it'll sand back after curing, but I'll not make this mistake again.
     
  5. lumberjim

    lumberjim TDPRI Member

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    It got worse. Much worse
    As soon as the lacquer hit the paint... [​IMG]
     
  6. Silverface

    Silverface Poster Extraordinaire Ad Free Member

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    Are you saying lacquer over enamel?

    Or the reverse?

    That wrinkling looks like lacquer sprayed over enamel. The usual problem with enamel over lacquer sanding sealer is poor adhesion - unless the sanding sealer was sprayed too heavily. Then you can have solvent entrapment, and as the solvent leaches out it will "massacre" the enamel from underneath!

    But fully dry lacquer sanding sealer has nothing in it that will attack enamel. As it dries by evaporation all the solvents SHOULD be gone.

    Enamel just does not adhere very well to it because it's too hard. It might get some mechanical adhesion if sanded very aggressively.

    My question - why are you using enamel as a finish? It has poor solvent resistance and color retention & the lowest durability compared to lacquer or polyurethane. It also usually "blocks" - sticks to other enamels, plastic and rubber - or discolors when leaned against those materials.

    I don't recommend it as a guitar finish.
     
  7. lumberjim

    lumberjim TDPRI Member

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    To answer your question : because I'm a dumb ass. I found the color I wanted and didn't even know there were different kinds of spray paint that would react poorly if not matched to the clear coat. That info must have gotten by me when I was watching you tube vids.

    Now I know
     
  8. philosofriend

    philosofriend Tele-Holic

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    Shellac is a pretty safe sealer. Use the white (dewaxed) kind, not the orange. Easy to apply, easy to sand, not toxic. Before putting the rustoleum enamal over it I would break the gloss with fine sandpaper to insure adhesion.

    The solvent for shellac is alcohol. Alcohol shouldn't attack enamel, but let it dry completely not only to be safe but to avoid later shrinkage problems.
    Lacquer thinner has stuff in it that is not friends with enamel. It wouldn't take much lacquer solvent hiding deep in the wood to come out and wrinkle enamal.

    If rustoleum recommends a certain sealer for wood for the color cans you're using, that would be the safest bet.
     
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  9. lumberjim

    lumberjim TDPRI Member

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    What kind of spray paint DOES work with lacquer clear coat? I wanted the light turquoise.
    [​IMG]

    This is the offending paint I used
    [​IMG]

    I had done a wash coat of 50/50 nitro lacquer and thinner, then the sealer, dried 5 days, then paint. I'm back to square one now, so what would you use? [​IMG]
     
  10. philosofriend

    philosofriend Tele-Holic

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    The answer is: opaque colored nitro lacquer. Stewmac and Reranch are two sources. That is assuming you are using nitro lacquer clear coat. If you have acrylic lacquer, you have stick with it for both the color and the clear coats. Since all the companies are always improving or cheapening their products, it is safest to stick with one manufacturer for the whole process.

    Lumberjim, that thing looked so good in the blue, I would have called it done!

    Rustoleum makes a "crystal clear" in that exact line of paints you used. You could use that for your clear. But, like Silverface said, enamels are kind of soft and not durable. Lacquer looks and feels more like a guitar. In my experience you can not sand a non-catalyzed enamel, it is too soft and sticky.
     
  11. Flakey

    Flakey Friend of Leo's

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    If I were you I would get that paint out of the control cavity as well. Pick your paint solvent and use a small wire brush to get in it out.

    You have a couple of ways to do this:

    Wash the body thoroughly with mineral spirits and let dry for 3 days.
    Get a can of vinyl sanding sealer. Some are great others not so much. DO NOT USE DEFT BRAND! Its never dries.
    The best would be Behlen's sanding sealer for guitar:

    h3918-2c97ed3238034c140cbbd8753c62b5e1.jpg

    Next. let the sealer dry a day at least and sand to 320 grit.

    Now you have choice you can paint your color coat directly onto the sealer. Like Gibson does or prime the body Like Fender used to do.

    If I were you I would prime the body using white sandable primer. I use Dupli-color. It plays well with just about any acrylic lacquer paint.

    Both Fender and Gibson used acrylic Lacquer under their nitro clear coat which is more acrylic than nitro these days. :twisted:

    It can be found in just about any auto store. One can is all you need. It relatively cheap about $7.00 YMMV.

    Primer.jpg

    Let your primer dry a day at the least but longer is better and sand smooth to 320 grit. A couple of light passes with the sand paper is all you need to do. Any sand throughs cover again with left over primer.

    Now here is the most complicated part, sourcing your color coat:

    Most rattle can manufactures, (Duplicolor Perfect Match product line is what I have used) use acrylic lacquer for their touch up sprays.
    The problem is most companies make paint for the most recent car colors used in the last 5 years and by and large lately they are mostly metallics. It looks like you are using a non metallic color paint. Very close to what Fender called "surf green".

    So your easiest choices are: 1) Change to a metallic and find something in the same shade or 2) Order a can of Surf Green from Reranch. I did a Sonic Blue Strat some years back and one can is all I needed.

    A more complicated way but will get you exactly what you want is to take a 3"x 3" color sample of your current spray and taking into an autobody paint supply, they will scan it and their computer will mix out a pint or whatever size you want. At some locations they will even load some of it into rattle cans for you but comparatively this is expensive and you will have much more material than you need for one body.

    Whatever choice you make the application of your color coat will be the same; 3 overlapping passes = 1 coat is the general rule depending on your technique. Let is gas out over a couple of days between each coat to be on the safe side.

    After your 2nd and, if needed, 3rd coat has dried completely you can now apply your clear coat.

    I strongly recommend you get Behlen's String Instrument Lacquer if you want nitro! It has more durable resins in it.

    One can maybe two cans should do it. They run about $13.00-$14.00 a can plus shipping.
    Woodcrafters sells the sanding sealer and lacquer so order them together and save on the shipping charges.
    I think Behlen's is also the retail line name for Mohawk finishes so you might want to check the Googles to source the product from Mohawk to save a few bucks.

    149254.0.jpg

    Follow the rule of 3s for applying you clear coat. Maybe sand lightly your between your second and third coat of clear with 400 grit if you have some orange peel. Make sure to wipe all the dust from the body before applying the next coat.

    Time is your friend in all this !!! The more time you have between for all your coat applications to gas out the better chance you have for avoiding problems.
     
    Last edited: Feb 18, 2019
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  12. lumberjim

    lumberjim TDPRI Member

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    Thanks, very much for taking the time to post that info. It's a huge help. I will probably be re reading it along the way. SERIOUSLY, thanks!

    oh, what's the rule of 3s as it pertains to clear coats?
     
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