Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com

Sanding before clear, blushing help please

Discussion in 'Finely Finished' started by Jazzybb17, Aug 24, 2017.

  1. Jazzybb17

    Jazzybb17 TDPRI Member

    Age:
    24
    15
    Jul 11, 2017
    Essex
    Hello there,

    I've finished spraying a Strat body with Sonic Blue nitrocellulose lacquer. All was going well but the final coat I sprayed in humid conditions and I've noticed some shiny patches mostly on the back. At first I thought they were finger prints but after researching I think it's blushing. So what I've done is waited a day and sanded the back with 800 wet sandpaper. The patches seem to have disappeared and the back is very smooth but you can see the marks from the sand paper if you look in the light.

    My question is do I need to spray another coat of sonic blue to cover these sanding marks/scratches or because I only used 800 grit will the clear coats cover it?

    Thanks for taking the time to read this I've looked online but can't find the answer specifically.


    Thanks,

    Jon
     

  2. R. Stratenstein

    R. Stratenstein Doctor of Teleocity Silver Supporter

    Aug 3, 2010
    Loganville, Ga.
    You could try spraying some lacquer thinner on it and see if that flows out the surface, or my go-to lacquer finish-fixer, Blush Eraser. Available through Amazon, Highland Woodworking, I think Woodcraft, and other outlets. A bit pricey, it's basically lacquer thinner with retarder, and a little goes a long way. It may work better to flow out the finish and get rid of small scratches better than straight thinner. And if you get any future blushing, well, this is the bomb.

    [​IMG]
     
    Jazzybb17 likes this.

  3. Jazzybb17

    Jazzybb17 TDPRI Member

    Age:
    24
    15
    Jul 11, 2017
    Essex
    Ah I see thanks for the prompt reply, I'm in England and can't seem to find that make but I'll have a look around. Just one more question where I've sanded the colour coat the scratches aren't really scratches but it looks like darker and lighter lines I'll try and take a picture. I'm just wondering would this need another coat of blue or would the clear sort this because I'm running out of blue. Thanks again

    Jon
     

  4. Jazzybb17

    Jazzybb17 TDPRI Member

    Age:
    24
    15
    Jul 11, 2017
    Essex
    Here's the pic
     

    Attached Files:


  5. R. Stratenstein

    R. Stratenstein Doctor of Teleocity Silver Supporter

    Aug 3, 2010
    Loganville, Ga.
    Yes, as best as I can see from the photo, I think I'd shoot another color coat, keeping the body flat so it will level well, and hopefully avoid having to sand the color coat.

    Are you aware of Rothko and Frost? They seem to be one of the better, more knowledgable UK suppliers of guitar finish materials. I would think if you contacted them, they could provide you good information and materials for dealing with blush in the future. I know several UK members here who have spoken well of R&F, maybe some other UK folks will chime in with others.

    And oh, yes, regarding your color coat. If the aerosol can is beginning to get low, warm it before spraying in a bath of hot water. This helps pressurize it resulting in better atomization, and lessens the chance of spitting.
     
    Grux likes this.

  6. Jazzybb17

    Jazzybb17 TDPRI Member

    Age:
    24
    15
    Jul 11, 2017
    Essex
    Thanks again Rick. I'll give it another coat and use the bath method as last time I used a can with not much in it sputtered. I just looked up that website and have never heard of them but will keep them in mind for further purchases.

    Thanks for the help,

    Jon
     

  7. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

    Age:
    65
    Mar 2, 2003
    Lawndale CA
    As previously mentioned - don't sand. But if the blush is present and/or you have already sanded and can't tell, do not apply another coat! You'll likely trap the moisture in the system (once applied there are no "coats" with lacquer.

    Misting
    a blush reducer is the only positive way to deal with it short of sanding the color off and starting again. Once it's there, light sanding to remove it often traps some of it - it's not visible, but probably will be later.

    DO NOT "spray" blush reducer or use lacquer thinner - lacquer thinner often does not release the moisture as it's far slower to flash off and if you apply enough to release the blush it often fouls the coating. Blush reducer (or eliminator - there are several names and "speeds") will cause nasty runs quickly if "sprayed". - it has to be misted.

    You just float a quick, very light fog of it over the area. Don't spray or even fog it "at" the blush or you'll screw up the finish. It needs to lightly drift down to the surface.

    If you are simply fixing scratches - don't. The clear will melt them away.

    Also - unless there are runs or damage don't sand the color coat. The color coat should be reasonably smooth without big bumps and other inconsistencies - if bumps/lumps are present there's a problem with spray technique and sanding won't fix it. It usually makes it worse as the clear ends up applied inconsistently and has to be sanded far too much, often ending up right through to the color.

    The only part of color coats that is sanded are runs or when hairs or dirt are on the surface. - which should not be there anyway. That requires more coating afterwards in most cases.

    But the clear melts into the color coat, and applied correctly it evens out minor inconsistencies. Major inconsistencies in the color coat are only sanded to remove most of it and respray - not as "prep" for the clear.

    There also should be very little sanding of the clear coat. Roughly speaking, if you can't start wet sanding with 1000 and be done working through finer papers in 20 minutes or so the clear was not applied properly - more and heavier coats should solve it.

    Many experienced finisher don't sand at all - once the clear has dried for 3-5 days (depending on weather) it goes straight to cotton buffing wheels and stick-type polish. You may not be at this point when you finish coating work, but if it's nice and smooth just forget sanding - all it will do it reduce the thickness.

    Hope that helps.
     
    Last edited: Aug 26, 2017
    Jazzybb17 likes this.

  8. Jazzybb17

    Jazzybb17 TDPRI Member

    Age:
    24
    15
    Jul 11, 2017
    Essex
    Thanks for taking the time to type that Silverface. It's really helped my understanding. I can't seem to find blush reducer anywhere online in England. I've been reading about blushing and have found that most people say it's more of a cloudy white patch, could what I think to be blushing be either where I've touched the guitar before spraying as on the back they were shiny spots after I sprayed the coat and let it dry, not really cloudy. Which I have since sanded with 600. On the front it was more of a shiny line I'm not sure if maybe that was where I've missed a bit of something but I wouldn't call any of it cloudy or white.

    Could I use white spirit to wipe it before spraying?

    Thanks all for the help,

    Jon
     

  9. Jazzybb17

    Jazzybb17 TDPRI Member

    Age:
    24
    15
    Jul 11, 2017
    Essex
    Can't really see it in the photo but over on the left side you can king of see the line I'm talking about and just under the bridge are some shiny patches.

    Thanks,

    Jon
     

    Attached Files:


  10. Festus_Hagen

    Festus_Hagen Tele-Meister

    Age:
    51
    116
    Jul 6, 2016
    Jeff City, Mo.
    I would try a coat of clear over it first thing. I think those will cover right up. If not, you have to do something with it anyway.....


    I had my clear do the same thing really bad once. As soon as I pushed the nozzle I saw the spray was not right so I stopped immediately, but there were a few spots. I let them flash off and dry for ~ an hour and lightly sprayed those areas and they went away. That was a trick I learned online somewhere, maybe here .

    Good luck!
     

  11. Jazzybb17

    Jazzybb17 TDPRI Member

    Age:
    24
    15
    Jul 11, 2017
    Essex
    Thanks Festus! I'll give that a try, how long would you leave between clear coats as I've seen conflicting advice online?

    Thanks again,

    Jon
     

  12. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

    Age:
    65
    Mar 2, 2003
    Lawndale CA
    i can see a slightly darker area that looks like a spot of "dry spray" - a rougher area. If that's true sanding is unnecessary. The slight roughness is melted by the clear coats. "Shiny" areas are glossy; whitish, foggy and cloudy areas are blushing and will not be solved by additional coats - they would make it worse, trapping the moisture in the film. Blushing requires blushing reducer as previously noted. You can find it at professional/contractor paint stores that carry finishing and toning lacquers - not typical retail outlets or hardware stores.

    If you absolutely can't find it in a store or on the internet - pretty unlikely - you can sand, but it has to be fairly aggressive sanding to ensure you both remove the problem and don't puch moisture into the film that's left. Obviously, blush reducer or eliminator is a far easier and quicker solution.

    Respectfully, this is poor advice unless the exact problem can be identified. If it's moisture or surface contamination all this would do is compound the problem. It's never a good idea to spray more coating of any kind over an unidentified problem.
     

  13. Jazzybb17

    Jazzybb17 TDPRI Member

    Age:
    24
    15
    Jul 11, 2017
    Essex
    Ok thanks for the advice once again, I really appreciate it.

    Just to clarify the spots on the back weren't cloudy or white they were just glosdy spots that looked like I had touched it with greasy fingers after spraying although I didn't. So could what I thought to have been blushing just be where I've sprayed a bit dodgely or sprayed over where I've touched it with fingers.

    So if these shiny bits aren't cloudy or whitish then they shouldn't be blushing and I can spray clear to try and fix this?

    Thanks guys,

    Jon
     

  14. Festus_Hagen

    Festus_Hagen Tele-Meister

    Age:
    51
    116
    Jul 6, 2016
    Jeff City, Mo.
    As I said though, he has nothing to lose since he would have to sand anyway.

    Each to their own I guess. I like to solve problems.
     

  15. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

    Age:
    65
    Mar 2, 2003
    Lawndale CA
    "Shiny bits" are smooth areas - meaning they are glossier than the rest of it. That's actually how the whole thing should look! Unless you had oil on your fingers - in which case I have to ask, why were you anywhere near a finish job - or some other contaminant...and the surface is reasonably smooth without lumps, waves (stuff you can feel) then apply more color coats if you're not done building them yet - or start applying clear.

    No, he probably doesn't. Sanding the color coat is only done to remove runs or some contaminants (ones that are stuck in the film). If it's blushing it only needs blush reducer - if it's just a "touched" spot or another slight mar it's a judgement call.

    If it's serious, yes - you sand and apply another full color coat - minimum. But if it's very minor, i.e. there's not a detectable difference in mil thickness - leave it.

    And if there are no defects, just a slightly rough, inconsistent gloss look - that's pretty normal, and you *don't* sand. The clear coats are meant to even out the gloss. Sanding color coats invariably causes problems.
     
    Festus_Hagen likes this.

  16. Festus_Hagen

    Festus_Hagen Tele-Meister

    Age:
    51
    116
    Jul 6, 2016
    Jeff City, Mo.
    Agreed.
     

IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.