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major cracks in lacquer

Discussion in 'Finely Finished' started by moose13, Sep 1, 2017.

  1. moose13

    moose13 Tele-Holic

    510
    Nov 30, 2015
    USA
    I let this guitar sit for 8 weeks or so now after spraying as i have not had time to work on it, today when i grabbed it i noticed major cracks in the finish. I did some minor wet sanding before but was careful not to flood it with water, everywhere there is a hole i have a big crack in the finish. First of all what did i do wrong? and second how do i fix it? Really bummed about this. Thanks

    IMG_3401.jpg IMG_3402.jpg IMG_3403.jpg
     

  2. old wrench

    old wrench Tele-Meister

    moose,
    I'm not a coatings expert by any stretch of the imagination, but if you'd explain your finish schedule and the materials used I'm sure it would help in figuring out what went wrong. Just being honest, that looks like some of my failed finish work where I either used incompatible finish products or I didn't allow sufficient drying or curing time between coats.

    Best Regards,
    Geo.
     
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  3. moose13

    moose13 Tele-Holic

    510
    Nov 30, 2015
    USA
    So its been a while since i worked on it but from what i remember, sanded smooth added sanding sealer and lightly sanded, total of 8 or 9 coats of nitro from stewmac, drying a couple hours between and only 2 coats per day. Probably a week or so between coats. lightly wetsand once about half way through.
     
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  4. Journeyman22

    Journeyman22 Tele-Meister

    400
    Dec 11, 2014
    Piute County, Utah
    Big cracks, I dab in "Clear" nail polish. let each coat/layer dry at least 24 hours. Lightly color sand with 400/600 wet/dry sand paper. After enough coats this way you can completely fill in the cracks. Color sand, down 1000 wet/dry sand paper. Next rub by hand with fine white rubbing compound till clear luster is attained. Now wax, should look like new. MMV.
     

  5. netgear69

    netgear69 Tele-Afflicted

    Dec 21, 2012
    england
    The areas (holes) are exposed vunerable areas once the clear coat cures it shrinks ! and looking at that it looks like a thick finish temp changes will cause deep cracks you could drop fill them cracks but you will still see them
     
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  6. moose13

    moose13 Tele-Holic

    510
    Nov 30, 2015
    USA
    Thanks Journeyman
    This is my guitar so if there are some minor cracks i will chalk it up to experience, but hope to at least make it look decent
     

  7. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

    Age:
    66
    Mar 2, 2003
    Lawndale CA
    I've seen that quite often over 37+ years in the business. It usually results from one or more of: 1) applying each coat far too heavily (i.e. much heavier than the normal 3 light passes per coat); 2) excessive total mil thickness (i.e. a complete lacquer system rarely exceeds 4 mils dry film thickness - appx 8-12 coats @ 3 light passes each; 3) lacquer applied (or cured) in temperatures below 65 degrees and then exposed to temperatures over 75 within a few hours and left in that condition for some time, or applied at 70+ degrees and exposed to <60 overnight; 4) any lacquer exposed to cold temperatures - like air conditioned rooms - if applied and cured at >75 degrees

    the temperature numbers are approximate to give a general idea of what can happen. But each - or any combination - of film thickness examples can result in an overly-stiff film - which can crack like mad. Lacquer does not work well at excessive thickness, nor does it like temperature changes - especially if thick, where it becomes very unforgiving.

    There's really no way to fix it - cracks of that extent cannot be repaired. Small ones - possibly using the previously mentioned method. But not larger ones that are "spiderwebbing". And repairs would only be temporary - the problem isn't solved, you'd only be fixing a "symptom.

    hope that helps.

    Ps - If you don't mind - why is the finish so "wavy"? That's generally considered a defect that requires sanding (instead of going direct to the buffer) - which also helps even out mil thickness. Did you wet sand at all before polishing?

    Also - what's underneath the clear (stains/fillers/sealers) and how was the wood prepared? One other cause of cracking - especially with chipping - is poor adhesion.

    Edited to add - and the obvious difference in thickness between natural wood and stained areas - what went on in those areas and how were the different (coats?) controlled?
     
    Last edited: Sep 3, 2017
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  8. moose13

    moose13 Tele-Holic

    510
    Nov 30, 2015
    USA
    so these photos are before any wet sanding or polishing. Under the clear is colortone water based stains.
     

  9. Do Not wet sand with water. Use mineral spirits. If the cracks are all around holes, water is the likely culprit
     
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  10. harold h

    harold h Friend of Leo's

    Feb 15, 2004
    Blush eraser may re-melt those areas if it is a nitro type finish.
     
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  11. RodeoTex

    RodeoTex Poster Extraordinaire

    Sep 14, 2005
    Nueces Strip
    I agree with some above. The finish may have gone on too thick.
    The upper layers begin to dry before the lower ones. When the lower layers finally do start drying it cracks cracks the uppers.
    The holes just allow air in to facilitate this happening sooner.

    Sorry but it looks like a refin is in the offing.
     

  12. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

    Age:
    66
    Mar 2, 2003
    Lawndale CA
    Agreed. When a coating system - that has no individual "coats" (lacquer coats melt completely into each other) - is too thick and cracks are extensive, drop-fills with other materials are impractical and almost always re-crack; and if blush remover is applied heavily enough to melt the cracks low "valleys" usually result along with often-uncontrollable runs. Even very experienced finishers don't generally attempt that.

    If it's like this before polishing, sorry - it's a defective application. IMO - and I've been at this a very long time - you'd be wasting your time trying to fix it. Best to cut your losses, strip it and start over.

    But -

    1. What do you consider a "coat"? It's important to know to help you prevent a repeat of this.

    2. Why did you let it dry 2 hours between coats? If applied properly you don't need to wait longer than 10 - 15 minutes...assuming the temperature and humidity are suitable for application.

    3. Why did you wait a week or so between...I'm not sure what, as you said you waited 2 hours between coats. Did you wait a week between each 2-coat process? That's absolutely unnecessary - it'd be interesting to find out where you heard that was necessary to possibly prevent others from waiting odd times for no reason.

    This is also completely unnecessary. As all lacquer coats melt into each other, intercoat sanding is a waste of time. It also increases the chance of introducing contaminants, especially ones pressed deeply into the coating. If the coats are extremely wavy or if orange peel is present simply correct your spray technique in subsequent coats. The only sanding between coats that should take place is if hairs or dust specs are on the surface - which should be prevented anyway.

    When the finish is complete sanding is only needed if the surface is a bit wavy. Normally it should be smooth enough to polish without sanding except for a few spots here and there. If wet sanding is needed over the entire thing - especially any situation calling for a grit coarser than 1000 to start - there's a problem with the finish application.
     
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  13. Buckocaster51

    Buckocaster51 Super Moderator Staff Member Ad Free Member

    Age:
    66
    Jan 6, 2005
    Iowa USA
    Admin Post
    As others have said, your film thickness appears to be excessive. Water is not the best thing to use when wetsanding a guitar. I use odorless paint thinner.

    Chalk this one up to experience and try it again.
     
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  14. Aras Bruce

    Aras Bruce TDPRI Member

    Age:
    40
    94
    Dec 9, 2012
    Seattle, WA
    I don’t have a ton of experience but I noticed cracks like this the last time I wetsanded with water. I would go with your gut, water or moisture would be able to get in every one of those spots when you wet sanded. I just furthered my cracks and made it an aged/relic job.
     
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  15. moose13

    moose13 Tele-Holic

    510
    Nov 30, 2015
    USA
    thanks guys, i sanded it back to bare wood restained and let sit for months . Last weekend i sealed with sanding sealer and started spraying 1 light coat per day, i am now on day 3 and am seeing cracking again! I gotta be honest i think this will be a vintage cracked finish as i am not sanding back down and spraying a third time. I really dont know what is happening, i am using rattle cans this time as i have had good luck in the past. Light coats one per day. i am lost on this one. I have lacquered 4 other guitars without a problem. Thanks for any insight
     

  16. harold h

    harold h Friend of Leo's

    Feb 15, 2004

    As said above- blush eraser will re-melt and re-flow the finish.
     
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  17. dan40

    dan40 Tele-Holic

    870
    Aug 19, 2015
    Richmond Va
    Are you using the same can or brand of lacquer on this second attempt?
     
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  18. drmmrr55

    drmmrr55 Tele-Meister

    Age:
    62
    220
    Aug 20, 2017
    Federal Way, Washington
    I'm not real knowledgeable about guitar finishes, but I have painted a few motorcycles and cars, and one thing I DO know, is if you spray lacquer OVER enamel, it will crack. Whether this is the case with your project or not, I don't have enough info to accurately conclude that, but it is a fact, because the 2 different finishes will expand/contract at different rates with temperature changes. I think enamels are much more flexible than lacquer, and less likely to check/crack, which is (partly), why so many guitars are now coming with poly (enamel) finishes on them. The other reason being environmental.
     
    Last edited: Mar 14, 2018
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  19. old wrench

    old wrench Tele-Meister

    Moose was real clear in stating that he sanded back to bare wood, then re-stained, applied sanding sealer, and then three (3) coats of lacquer, and now, the dag-gone cracks are back.

    This has got to be frustrating!

    What kind of stain, sanding sealer, and finish coat did you use on the original finish, and did they change on the refinish?

    Best Regards,
    Geo.
     
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  20. +2. Moisture gets on the bare wood and the wood expands while the lacquer does not. The result on thick lacquer can be cracking.

    Lots of other good insight in responses as well.

    Something I have done with some success before resorting to a full refinish. Take a razor tip and lighly score each crack. Brush retarder or thinner in each crack to soften. Drop fill each crack repeatedly until level. Spray a wet coat of retarder, or heavy reduced lacquer, over the area. Let cure, wet sand with mineral spirits or naptha.
     
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