1. Win a Broadcaster or one of 3 Teles! The annual Supporting Member Giveaway is on. To enter Click Here. To see all the prizes and full details Click Here. To view the thread about the giveaway Click Here.

Tiny Bubbles...

Discussion in 'Finely Finished' started by TelZilla, Jul 28, 2019.

  1. TelZilla

    TelZilla Friend of Leo's

    Posts:
    3,724
    Joined:
    Jan 21, 2007
    Location:
    Cleveburg, USA
    No, not Don Ho.

    Warmoth Ash body. Grain Filled and sanded back 2X. Two coats of Reranch sanding sealer, sanded back between each. Light coat of Reranch Butterscotch Blonde. Left it looking like this:

    [​IMG]
    So I waited a day and began spraying clear. Using rattle cans of Behlen's stringed instrument lacquer.

    • Did three coats with about 90 min between on Friday. Let it hang to dry overnight.
    • Sat AM I had these tiny bubbles in a few small spots (upper bout on the neck side and right on the butt behind the bridge. Weird.
    • So I sanded those spots with some 800 grit paper, and got them flat, but the butterscotch blonde came off with it. So I shot a little bit of butterscotch blonde just to cover those spots and left it overnight.
    • Looked OK this morning (Sun AM), so I did another coat of clear
    • After 2-3 hours of drying, the little bubbles reappeared in the same spots. Here's what they look like:
    Bubbles.jpg
    IMG_0132.jpg
    IMG_0133.jpg

    So what's going on here? How should I address it?
     
  2. dogmeat

    dogmeat Friend of Leo's

    Age:
    70
    Posts:
    2,273
    Joined:
    Oct 12, 2017
    Location:
    Alaska
    something is gassing off underneath. go back to the butterscotch and get it how you like, then leave it for several days.... maybe a week.
     
    Flakey likes this.
  3. TelZilla

    TelZilla Friend of Leo's

    Posts:
    3,724
    Joined:
    Jan 21, 2007
    Location:
    Cleveburg, USA
    Makes sense. What grit would you suggest for sanding back to the butterscotch?
     
  4. dogmeat

    dogmeat Friend of Leo's

    Age:
    70
    Posts:
    2,273
    Joined:
    Oct 12, 2017
    Location:
    Alaska
    I'd probably start with 280 or 320.

    can you tell which layer is causing it? it could be in the clear coats too. I've shot a lot of aircraft dopes (they are very close to laquer) and they will pinhole and bubble if there isn't enough cure time between coats. in rattle can you don't have any choice of thinners, so you have to go by testing. and film thickness matters... one guy's coat is worth another guy's 2 coats
     
  5. TelZilla

    TelZilla Friend of Leo's

    Posts:
    3,724
    Joined:
    Jan 21, 2007
    Location:
    Cleveburg, USA
    Well, after the first time I sanded off the bubbles, the butterscotch came off. By that I mean that the surrounding areas were still butterscotch, but the little dots where the bubbles had been had no butterscotch.

    I suppose that means it's below the butterscotch layer? but then, the bubbles didn't show up until I started the clear coating, so I'm not sure.

    I was shooting fairly heavy coats. maybe I need to do lighter coats and only one a day...
     
    Flakey likes this.
  6. dogmeat

    dogmeat Friend of Leo's

    Age:
    70
    Posts:
    2,273
    Joined:
    Oct 12, 2017
    Location:
    Alaska
    yep.... sounds like its in or below the Butterscotch. re-do that and wait longer before going with the clear. maybe bake it at low temp. your base coats need to be really cured out to resist the solvents in the lacquer, they are quite active (ketone/acetone family). and yes, thinner coats with more time between will probably help, at least for the initial coats. good luck, its a nice looking piece
     
  7. pwhite

    pwhite TDPRI Member

    Posts:
    79
    Joined:
    May 3, 2011
    Location:
    Liberty, SC
    I had an explorer build do the same thing when I first started shooting lacquer I think I did to heavy of coats to fast but not sure if that was the cause. I try to do more lighter coats and wait longer between them now. I have not had one do it since.

    2011-07-24_17-59-53_43.jpg
     
  8. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

    Age:
    68
    Posts:
    9,787
    Joined:
    Mar 2, 2003
    Location:
    Lawndale CA
    HOW did you apply the coats - and did you apply the whole system from prep to buffing on scrap before starting on the real thing? If not - HIGHLY recommended. I still do it after 50 years if ONE product in the system is something I have not used.

    That is a LOT of color for 3 coats. You undoubtedly have solvent entrapment.

    Did you apply full coverage coats? IF so, that's the problem - it's too thick, "surface dries" trapping solvents inside - and as it eats up the solvents ned to escape.

    Normal application method for those that don't do finish work often should always consists of 3 VERY light passes per coat - and a single coat should be quite light and not cover very well at all.

    You really should not get coverage over a sealed/filled surface until the 5th or 6th color coat. Reranch lacquers are conventional (unlike Deft and Colortone) and dry in 30-60 minutes per coat.

    And when applied LIGHTLY an hour dry time gives the solvents plenty of time to escape.

    Unfortunately, to get a consistent finish you will need to strip that back to bare wood. Use stripper - sanding will take forever and leave you with an uneven surface!

    At the same time, find some similar scrap at Rockler or a hardware dealer, cut a cutaway in it, sand it smooth and apply the ENTIRE system.slowly and carefully. And remember - lighter is ALWAYS better!

    Last - just in case, pick up (at Harbor Freight) or order a moisture meter and test the moisture content of the body AFTER it's stripped. There is an outside possibility there is a moisture problem, which looks the same! If it's over 11% DO NOT PAINT! Some feel 15% moisture content is safe, but I have investigated dozens of failures at 12-14%. Personally, I use 8% as the cutoff.

    Hope that helps!
     
    Last edited: Aug 3, 2019
  9. TelZilla

    TelZilla Friend of Leo's

    Posts:
    3,724
    Joined:
    Jan 21, 2007
    Location:
    Cleveburg, USA
    Not sure what this means. It wasn't three coats of color- it was one light coat. Three coats of clear.
     
  10. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

    Age:
    68
    Posts:
    9,787
    Joined:
    Mar 2, 2003
    Location:
    Lawndale CA
    My mistake. I misread the color application.

    It would still be helpful to know exactly how each coat was applied, i.e. describe your method for applying a "light coat of butterscotch" and each clear coat.

    the only exception to the below would be if the moisture content of the wood was too high as described above.

    But to repeat -

    The problem I see based on what's been described so far is that a single coat of blonde lacquer - or ANY color - should not provide full coverage. "Paints" - like enamels and acrylics - can be applied that way, but with lacquers - especially when using aerosols, which provide poor mil thickness control - the best system is usually 3 VERY light passes per LIGHT coat.

    And complete flow and coverage (as lacquer melts into itself) generally does not occur until the 3rd or 4th coat. When applied this way, ReRanch and most other traditional lacquers will generally dry in 30-60 minutes per coat (often 15 minutes in warm weather).

    This is great when they are applied THIN - the solvents gas off (evaporate - which is the only way lacquers dry....there is NO "cure time") and it's ready for the next coat.

    But it's terrible if the material is applied even a little bit too thickly - and "full coverage" from a single coat is always too thick unless you are an experienced applicator using e something like a heated HVLP and the proper solvent additives.

    If the coat is too thick the solvents evaporate from the top of the freshly-applied layer - "surface drying", or "skinning over".

    When this happens liquid solvents are trapped under the dry top of the film. They can't evaporate and under the best conditions the film stays soft; but even light heat causes them to expand under the film, creating bubbles and blisters.

    It may have only been the color coat that was applied too thickly, but generally if one coat is applied thick - like paint - ALL coats were applied that way. So during reapplication I strongly suggest applying the ENTIRE system on scrap wood - all the way through to buffing - before working on the guitar again. Refine your technique and make sure you aren't applying coats too thickly.

    As far as removal goes - in your case it's obvious the blonde is too thick if only one coat was applied, so at minimum sanding back to the primer/sealer coat will be required.

    I hope that was clear. If not, please ask questions.
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.