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Thread: lacquer problem

  1. #1
    Registered User David Houchens's Avatar
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    Default lacquer problem

    Howdy everyone. I haven't posted for quite some time.
    I have built around 85 mandolins and close to 30 guitars and have never had the finish problem I'm seeing on my last mandolin.
    I used Behlens nitrocellulose lacquer out of the same gallon can I did the last couple from.
    There are check cracks in the lacquer all the way down to the shellac sealer. I followed the same spray schedule I've done for 17 years. the checks are just scattered around.
    Now I was wandering if any of you who spray nitro have experienced similar checking.
    Thanks

  2. #2
    Registered User sunburst's Avatar
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    Default Re: lacquer problem

    How old is the can of lacquer?
    I had checking problems using the last half of a 5 gallon pail of McFadden's lacquer. I quit buying 5 gallon buckets and only never buy larger than 1 gallon cans. I can only assume that plasticizers degrade in the can over time.
    If it is new lacquer it might be the fault of the manufacturer (as we know too well) and good luck getting them to admit it if it is.

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  4. #3
    Registered User David Houchens's Avatar
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    Default Re: lacquer problem

    Thanks John. Wow, that was quick. I've only had it for 5-6 months I think. Though who knows how long WoodCrafter's had it. Now hearing Mohawk grabbed up Behlins makes me wonder. Guess I'll just strip it and have another go round.

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    Registered User sunburst's Avatar
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    Default Re: lacquer problem

    I think Mohawk and Behlen have been one and the same for a very long time. For what it's worth, I now use Mohawk lacquer with few problems (just the usual ones).
    Yeah, WoodCrafters could have had it for a long time, but is there a date code that tells you? Might just have to get a new batch.

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  7. #5

    Default Re: lacquer problem

    I ran into a similar post on another forum some years ago and they never got to a conclusion. I've been using the same gallon of Mohawk on the few instrument I've built in the last 4 years here in NJ and its still the most awesome stuff ever. I'm not careful with it either. Could you have had some sort of contamination during mixing or in your gun or your compressor? ...as in some non-lacquer product you may have used? I wouldn't suspect the lacquer. The pigment/tint, the thinner,??? Lacquer thinners are quite variable and there is no true standardized recipe. Long ago, I used straight acetone as lacquer thinner for an automotive lacquer.

    How soon did these checks appear after the finish was applied? Real early checking without years of venting is just odd. I just kinda assume that lacquer remains kinda soft for the first months and quite forgiving to any wood swell from severe humidity changes. How much powered polishing did you do, any difference in your method? I'm sure you would have mentioned any different sort of methods you may have applied to get a faster cure.

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  9. #6
    Registered User David Houchens's Avatar
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    Default Re: lacquer problem

    Wrnchbndr, No odd mixes, tints or additives. Just shellac flakes melted in alcohol sealer, Behlin lacquer and a real slow evaporating lacquer thinner. Same as I've been using. The finish has cured for 30-40 days. Maybe my shellac sealer curing at a odd rate? I'm at a loss. I tried blending the lacquer back with thinner but being a new instrument I don't want it coming back for checks that may open down the road. I want it right. Strip and try new lacquer I guess. Thanks for your reply.

  10. #7

    Default Re: lacquer problem

    If you discover what happened, please let us know.

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  12. #8
    Registered User sunburst's Avatar
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    Default Re: lacquer problem

    Quote Originally Posted by Wrnchbndr View Post
    If you discover what happened, please let us know.
    My money's on 'we never figure it out'.

    BTW, I amalgamated the lacquer on some of the instruments with checked lacquer and the checks dissipated, but reappeared later. Yes, I think stripping and refinishing is the only solution to the problem.

    Edit:
    Disappeared, not dissipated. Spellcheck got me again.
    Last edited by sunburst; Oct-25-2019 at 11:27pm.

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    Default Re: lacquer problem

    an you put a photo of the checking up please?

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    Registered User fscotte's Avatar
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    Default Re: lacquer problem

    I like to think that the culprit is something in the spray gun itself. Clean those things throughly.

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  17. #11
    Registered User David Houchens's Avatar
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    Default Re: lacquer problem

    John MacPhee, I'll try to get some pictures. Until yesterday I was trying to repair them so I'll look for more. These were not noticeable until I was wet sanding

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  19. #12
    Registered User David Houchens's Avatar
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    Default Re: lacquer problem

    Fscotte, Spray gun is cleaned as I've always done but anything is possible at this point. Thanks

  20. #13

    Default Re: lacquer problem

    Any possibility of moisture getting into your air? That's the only other thing I can think of. I ruined a batch of several instruments I was refinishing with lacquer a few years ago because the air wasn't dry enough.

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    Default Re: lacquer problem

    Sorry to hear that David. Nothing like getting to the finish line building an instrument and having issues.

    Does not apply to your situation, but I recently learned the hard way that Cardinal lacquer does not like to sit on top of a shellac seal coat. Had similar issues on a guitar last year. Talked to a guy later who does finish work for a living and he told me that Cardinal does not like shellac.

    Hope you figure it out so it doesn't happen again.

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  24. #15
    Registered User amowry's Avatar
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    Default Re: lacquer problem

    Yes, Cardinal definitely does not like shellac. I learned the hard way too. I think shellac can in general cause problems under lacquer, especially if it's applied too thick. A very thin wash coat is probably fine (not under Cardinal, though). Shellac is great in a number of ways, but I don't use it as a sealer any more.

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  26. #16
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    Default Re: lacquer problem

    I'm having problems with cracks in my finishes on my last two mandolins. I used the Mohawk branded Behlen instrument lacquer from my local Woodcrafters. On the first mando the cracks were around the F holes and really didn't show up until buffing the finish. I figured I didn't seal the F holes well enough and moisture from wet sanding got under the finish. On the current mando the crack is in the middle of the top. It's been sitting undisturbed for a couple weeks. I don't know what I could have done to precipitate this. Click image for larger version. 

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    Default Re: lacquer problem

    I haven't paid close enough attention to give any advice about the OP's problem. But I can say this. The problem around the f holes is wet sanding without sealing the end grain. The wood swells from the water. The lacquer can't expand at the same rate and cracks. The same thing will happen in the tuner holes, even in ebony. Use a different lubricant in those areas.

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  30. #18
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    Default Re: lacquer problem

    While I'm rattling on, I don't use Cardinal lacquer. I use Mohawk. But I've never liked using shellac under nitro. I don't know who told me, but somebody said to use vinyl sealer. That's all I use on instruments that are going to be finished with nitro. I've never had a problem.

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  32. #19
    Registered User sunburst's Avatar
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    Default Re: lacquer problem

    Ive never had a problem with shellac as a sealer, but I have with vinyl sealer. Any small sand-through in the lacquer at any time in the finish process leaves an area of clearer looking wood. Not only does the inconsistency of that look bad, but it indicates to me that the vinyl sealer has a slightly cloudy appearance compared to shellac. As always, YMMV.

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  34. #20

    Default Re: lacquer problem

    I don't miss wet sanding, or seal coat/topcoat issues, at all. :-)

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  36. #21
    Registered User fscotte's Avatar
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    Default Re: lacquer problem

    You don’t need to wet sand, just sand.

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  38. #22
    Registered User amowry's Avatar
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    Default Re: lacquer problem

    After having problems with shellac under Cardinal, I switched to vinyl sealer, and I like it much better than shellac. A lot of the literature talks about shellac sealer “bringing out the beauty of the wood”, but I did several test boards of different species and colors comparing shellac and Seagrave vinyl sealer under Cardinal, and they were totally indistinguishable, but the lacquer adhered to the vinyl much better, and the vinyl sealed the dye better. I do use only two very thin washcoats of sealer, one before scraping the binding and one after. It’s hard to tell there’s anything on the wood.

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  40. #23
    Registered User slimt's Avatar
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    Default Re: lacquer problem

    Quote Originally Posted by dave vann View Post
    I'm having problems with cracks in my finishes on my last two mandolins. I used the Mohawk branded Behlen instrument lacquer from my local Woodcrafters. On the first mando the cracks were around the F holes and really didn't show up until buffing the finish. I figured I didn't seal the F holes well enough and moisture from wet sanding got under the finish. On the current mando the crack is in the middle of the top. It's been sitting undisturbed for a couple weeks. I don't know what I could have done to precipitate this. Click image for larger version. 

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    That looks like the wood moved and the clear did not.. how do you apply your clear? in stages or ?

    btw,, Nitro has a shelf life..

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  42. #24

    Default Re: lacquer problem

    $#@)!^& finish problems!!!!!!!!!!!!!!!!!!!!!!!!!!
    Spruce dork

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  44. #25

    Default Re: lacquer problem

    I've had that cracking and contributed it to the shellac. I use an off the shelf shellac and I think it was too old. A new can resolved the issue. I was unable to fix it with anything less than stripping it down. The lacquer is Mohawk.
    Click image for larger version. 

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