Dry sanding nitro?

Discussion in 'Finely Finished' started by Honza992, Mar 13, 2019.

  1. Honza992

    Honza992 Tele-Meister Silver Supporter

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    Hi All

    I normally use water based poly, but this time (for the first time) I'm using nitro to finish a guitar. I'm reaching the point of final sanding and I'm very nervous about wet sanding. If I wet sand with water I'm worried about grain raise and sanding with mineral spirits really doesn't appeal - I'm pretty sensitive to solvents.

    I then came across this:



    This guy says that with modern no-load abrasives, there's no need to wet sand, that you can dry sand.

    Any thoughts? Any idea what sort of paper he's talking about?
     
  2. jrblue

    jrblue Tele-Afflicted

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    I can only give my own experience. I damp sand and dry sand pretty interchangeably depending on feel. I avoid solvents, and detest mineral spirits, so I'm not doing that, ever. The guy in the video claims that you need to slosh water everywhere to wet sand. That's news to me; I guess I've been doing it wrong since I use only wet paper and a drop or two of water. I have never had a problem at all, and though the video talks about all the disaster stories out there, that's news to me. From my position, he's freaked out about something I have never experienced. I'm not afraid of dragons, either. On the other hand, I really do less and less wet sanding because I don't experience the need for it. If I let my finish dry sufficiently, sand lightly, let any heat dissipate, I rarely end up even going for the water. I use it to clean my paper and then maybe continue with that... I experience this video as an overreaction to a problem that does not, for me, exist.
     
  3. Ronkirn

    Ronkirn Doctor of Teleocity Vendor Member

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    Yes, 3M makes abrasives that work well on well cured Nitro... by well cured, I mean at least 3 weeks.. I've tried it on several and I'm making the move from wet sanding myself....

    rk
     
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  4. Ripthorn

    Ripthorn Tele-Afflicted

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    One thing that is key to both wet and dry sanding is to not use too much pressure. You can load up wet paper with too much pressure in a hurry. Everyone wants the magic bullet to make everything instantly easier, but somewhat by nature of DIY, we want cheap, too, and those don't necessarily go hand in hand all the time.

    That said, I need to wetsand a body tonight. Ron, what abrasives are you using now?
     
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  5. jrblue

    jrblue Tele-Afflicted

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    Ripthorn's comment on pressure for the win! That nails it, for me at least. Patience, a light hand, and the ability to both keep things level and to not sand through curves and corners is where it's at for me, and trumps everything. The abrasive materials we have on hand at present are simply fantastic compared to what I started with. Just use them lightly and take your time.
     
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  6. schmee

    schmee Poster Extraordinaire

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    I wet sand. Just use a spray bottle. Wipe the debris off often. Unless you haven't put enough on there will be no issue. If you haven't put enough on then you are going to sand right through to wood anyway.
     
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  7. RickyRicardo

    RickyRicardo Friend of Leo's

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    ^^That's what I do. I spray lightly, use very light pressure, clean the paper off by spraying and wiping it and don't have water everywhere. I don't have to change water in a bowl either. Also, I start at 1000 or 1200 grit depending on how smooth the finish is. This narrows down the chances of sand through. I finish up with 3000 grit Abralon sanding disks on my orbital with a tiny spritz of water before moving to compound.
     
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  8. Freeman Keller

    Freeman Keller Tele-Afflicted

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    I come from the 1960's hot rod era where half of a lacquer paint job went on the floor as sanding sludge. I'm also not a good enough finisher to lay down a perfect last coat, so I just automatically wet sand. I soak my sand paper for several hours, start at 800 and go up thru the grits to 2000, then polish on a wheel or foam pad with Megiuar's fine compound. All the sanding is by hand with light pressure, I try to let the abrasive do the work. I do the same thing on nitro or water born lacquer, which are the only finishes I use. The fact that it works makes me not interested in experimenting with anything else.
     
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  9. ben smith

    ben smith Tele-Meister

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    ive been spraying guitars for years it was my job at one point, i used tiny amounts of water and soap for a guitar once and still it cracked, it was not my error at all and from that day forward i just bought more sand paper and dry sanded, never again will i use water. it was my own guitar that cracked though thank god. it's just a case of saving money to wet sand, it works perfectly ok without water, if you use fine enough grit to finish there will be no problem. p.s sorry to be negative but i have watched many of this guys videos and i can't help but feel he is amateurish.
     
    Last edited: Mar 13, 2019
  10. telepraise

    telepraise Tele-Holic

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    Wet sanding for me. All the advice you got here is good, light pressure, high grit count, patience. For larger areas I use a small oval shaped piece of Ensolite sleeping pad foam wrapped in wet/dry paper to level compound curves. A cool thing about wet sanding is you can tell when you're down to a uniform surface because the paper just lets go and glides over the surface with no resistance. I have learned to go up one grit step from what I just used on the flat surfaces to hand sand corners and rounded edges (if I just used 800 on the body, I skip that grit and go to 1200 for edges) This has saved me from sand-through.

    One thing you should be aware of is that nitro coats burn in to each other and consolidate as they cure (great for sunbursting). For this reason, it also may shrink more than what you're used to from water-based. You can sand it out dead flat and buff it out, and months later shallow spots and joint lines you thought you had filled sufficiently reappear as the nitro shrinks and sinks in. Get it as good as you can before you start finishing. Enjoy the adventure!
     
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  11. Festus_Hagen

    Festus_Hagen Tele-Holic

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    Same here.
     
  12. Finck

    Finck Tele-Afflicted

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    I've tried dry sandpaper and didn't like it too much. It clogs a lot, and catches small balls of paint which tends to scratch the finish, requiring very frequent change and extreme care.
    Also, that nasty paint dust spreads everywhere.
    For me, wet sandpaper with water and detergent is the way to go.
     
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  13. Ronkirn

    Ronkirn Doctor of Teleocity Vendor Member

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    I'm using, 800, 1200, 2000 .. then on to the buffer.... pretty straightforward..

    r
     
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  14. Honza992

    Honza992 Tele-Meister Silver Supporter

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    And are there special 'no load' papers, or will all wet/dry paper be OK?

    Also, for those of you that wet sand how much prep are you doing? I've read about wax and using finish to line pickup/neck routs etc

    Thanks all for the responses, really useful.
     
  15. RickyRicardo

    RickyRicardo Friend of Leo's

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    I don't do any prep at all. I've never had an issue with swelling that I've noticed. If water gets anywhere near or in a hole I wipe it right away. I'm not saying it can't happen though. As you mentioned, finish in those areas help to seal it.
     
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  16. Ronkirn

    Ronkirn Doctor of Teleocity Vendor Member

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    this is typical of the 3M product that works with cured (thoroughly dried for the chronically pedantic) nitro.... 3M™ 00910 Hookit™ Finishing Disc . I haven't figured out 3M's product number yet but for the most part.. it's the white stiff.. the blue/purple will not cut jack... loads up faster 'n your PF Flyers in a cow pasture...

    And that's 800 grit... you'll hafta dig to get the numbers for other grits...

    rk
     
  17. Freeman Keller

    Freeman Keller Tele-Afflicted

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    I mask off some areas - cavities, predrilled holes, fretboards but otherwise don't do any "prep". I keep wax of any kind as far away from my finishes as possible.

    If you have worked on many factory guitars you would be surprised how many have polishing compound and other gunk in cavities and holes. I take the time to clean mine up when I am finished.
     
  18. Festus_Hagen

    Festus_Hagen Tele-Holic

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    Same here. If a body isn't pre-drilled, I wait until after I finish it to do the holes to keep water out of them, but otherwise I just wipe water away ASAP , and in a lot of cases, the grain filler will fill in the small holes so I don't even have to worry about those.

    I use 800- 2500 grit and flat-sand with dishwashing liquid and water. I rinse the paper often to keep the pores clean and don't put a lot of pressure on the paper. I just let the sanding block do the work.

    I also sand in circles when I get down to 1200 and beyond.
     
  19. Silverface

    Silverface Poster Extraordinaire Ad Free Member

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    You can find all sorts of opinions on the internet.

    *IF* the surface is rough enough that you need to wet sand (if it's reasonably smooth don't - just buff and be done with it. Wet sanding is meant to fix rough/inconsistent application):

    1. Water will NOT raise the grain unless you left bare wood exposed. As far as holes go, use Google - there are plenty of ways to temporarily prevent water penetration. It's simply not a problem.

    2. If you are sensitive to mineral spirits wear nitrile gloves. If fumes bother you use what you should bee using when working with ANY solvents - the proper cartridge type respirator and fill-coverage goggles. Read the MSDS any time you use a solvent or solvent based product and take the precautions laid out there - that's the point of an MSDS.​
     
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  20. Vizcaster

    Vizcaster Poster Extraordinaire

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    I find it easier to see when the shiny divots disappear when sanding level without any water or lubricant. Have a vacuum nearby and periodically remove the dust from the workpiece and from the sanding block. Use an air srubber in the room. Wear a dust mask. IMHO it's less messy than wet sanding.

    Once the surface is level and you're working up the grits before buffing, there's really not a ton of material being removed so I don't see much of a hassle doing it dry.

    Another point is that with water based lacquers they sometimes don't like to be wet sanded until they're fully cured - I got really exaggerated witness lines wet sanding some materials that were not a problem when sanding dry. Now I mostly use Emtech EM6000 which burns into itself without witness lines; but it's really 6 or 7 days before you can sand and buff.

    Another issue unfortunately for water based lacquers is that they recommend against using "stearated" papers but unfortunately there's stearate (soap) in most papers whether or not they're called out as "no load." So that complicates things for sanding between coats; but honestly the technology of water based finishes has come a long way and I haven't had any problems of the finish crawling or being contaminated by stearate from sanding between coats (which I do after the first few sealer coats and then of course whenever there's a run or sag or blemish).

    3M Frecut Gold aluminum oxide is my favorite no-load, open-coat paper for dry sanding and it's less expensive than wet-dry silicon carbide.
     
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