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Paint help! What Grit Sandpaper?

Discussion in 'The Hokey Ass Message Board' started by FIFTY2, Oct 5, 2009.

  1. FIFTY2
    Joined: Apr 9, 2008
    Posts: 340

    FIFTY2
    Member

    Ok, heres the deal, I think Im getting close to being ready for my top coat. Heres what Ive done:

    Epoxy primer
    Filler
    More Epoxy primer, followed by Hi fill Primer
    Blocked with 80, then 180.

    Just shot another coat of Hi fill primer, I think my cars straight enough for paint, but I need to know how fine a grit of sand paper to use. I was gonna go.

    180, then 320. then ?????????

    Do I have to wet sand?

    Thanks

    [​IMG]
     
  2. Abomb
    Joined: Oct 14, 2006
    Posts: 1,659

    Abomb
    Member

    I'd go with at least 400 or finer, depending on your topcoat. Have you shot a guidecoat before block sanding ?? You say "I think it's ready" with a guide coat and some more blocking you will KNOW if it's ready.......
     
  3. bibb86
    Joined: Mar 23, 2009
    Posts: 65

    bibb86
    Member

    block sand 320 with a guide coat then sealer then paint
     
  4. autobodyed
    Joined: Mar 5, 2008
    Posts: 1,943

    autobodyed
    Member
    from shelton ct

    if you shot just one coat of primer, odds are your going to sand all of it off again, maybe should have put at least 2 or 3 coats. sand it with 320 first to see if goes thru, if not finish it with 500 and then a nice coat of sealer before paint. any body work that comes thru ( bondo or putty ) should be spot primed and resanded before sealer. good luck.
     

  5. 8flat
    Joined: Apr 2, 2006
    Posts: 1,380

    8flat
    ALLIANCE MEMBER

    I use 400, sometimes go over it by hand with P-600. 360 can show sand scratches if you're not careful, such as where the edge of your paper leaves small 'gouges' in the primer.

    Like Abomb said, use a guide coat and run over it with a block to make sure you don't have any low spots, high spots, or sand scratches showing through.

    And yes, use water, lots of it, to make sure you keep the paper clean.
     
  6. barnescole
    Joined: Dec 2, 2008
    Posts: 138

    barnescole
    Member

    i second the 400 minimum suggestion, followed by a sealer.
     
  7. FIFTY2
    Joined: Apr 9, 2008
    Posts: 340

    FIFTY2
    Member

    Yeah, When I say another coat of primer i mean 2 total.

    What Shoud I start with 180 and progress or go straight to something finer?

    Thanks for the help!!
     
  8. Steelsmith
    Joined: Feb 5, 2007
    Posts: 581

    Steelsmith
    Member

    If you are wet-blocking, you may want to use an additional 'step' between 180 and 320. 220-260 would be good, and I'd be using a long block to do the wet blocking. Guide coat should be used between each grit change. That lets you know when you have sanded out all of the previous grit scratches, and have smoothed out all of the undulations in the bodywork.
    If you are using catalysed urethane hi-build primer, you don't have to use a seal coat. You can, but I'd only do so if I had broken the surface of the primer and hit bondo. If you are doing that, you weren't ready/weren't straight in the first place, and you should get the blocking straight before moving up in grit.
    Avoid applying too much paint without blocking it back off. Keep your final paint job as thin as you can, without breaking through. Extra mil's of thickness only make a paint job easier to damage.

    Dan Stevens
    dba, Steelsmith
     
  9. FIFTY2
    Joined: Apr 9, 2008
    Posts: 340

    FIFTY2
    Member

    Im planning on only dry sanding if thats possible. I plan I guide coating between each blocking session.
     
  10. Steelsmith
    Joined: Feb 5, 2007
    Posts: 581

    Steelsmith
    Member

    Oh, and add a little Ivory dish-soap to your sanding bucket/water. It helps the sandpaper to glide across the paint. Don't use just ANY dish-soap! Some have lanolin in them. Lanolin is for 'nice hands', it leads to fisheyes in a paint-job! You want to read the dish-soap labels. Ivory used to be 99-44/100ths% pure! Times have changed and that may no longer be true either ...

    Dan Stevens
    dba, Steelsmith
     
  11. MarkzRodz
    Joined: Sep 12, 2009
    Posts: 533

    MarkzRodz
    BANNED

    When I do that it never fails that I get beads on the paper that gouges the surface and leads to more trouble.
    If you are affraid of too much water,, I use a spray bottle with a drip of soap (no lanolin/conditioners) and a whole roll of paper towells. Do a section at a time.
    No need to guidecoat that much.
     
  12. Steelsmith
    Joined: Feb 5, 2007
    Posts: 581

    Steelsmith
    Member

    I'm assuming you are painting in your garage? If that is the case, wet-blocking will help with the dust issue you will be facing. Dry-blocking will just add to the problem. However if you are carefull to blow everything off throughly before during and after masking, you can still do a decent job.
    After you are done with all of your block sanding at 320, I like to do a light recoat(last coat of primer) guide coat and DA using 400 grit. It gives a good final 'tooth'.
    You haven't said what top-coat you are using. Single stage, base-coat/clear-coat?

    Base coat/clear-coat likes a little finer grit for a final 'tooth'. Stopping at 400 may leave some fine sand scratches. I'd final block 'wet' at 600 for BC/CC. If you go with dry sanding, you go dry ... it's largely personal preference.

    Dan Stevens
    dba, Steelsmith
     
  13. barnescole
    Joined: Dec 2, 2008
    Posts: 138

    barnescole
    Member

    in my opinion, you gotta wet sand when approaching your final coat. you'll find it much easier....i actually enjoy sanding when it gets to that point. :rolleyes:
     
  14. zman
    Joined: Apr 2, 2001
    Posts: 16,595

    zman
    Member
    from Garner, NC

    one of the things I like to do is use different color primers (epoxy, high build, sealer) gives me a better idea of what's going on blocking.
     
  15. autobodyed
    Joined: Mar 5, 2008
    Posts: 1,943

    autobodyed
    Member
    from shelton ct

    wet sanding is the only way to go. your job will come out straighter and you'll be able to do it in half the time and half the material! you'll be clogging the paper every 2 passes. like said before, add a little soap to the water and have at it. it's really not that messy if you clean every panel after sanding, plus you will be much more satisfied with the final results!
     
  16. SakowskiMotors
    Joined: Nov 18, 2006
    Posts: 1,242

    SakowskiMotors
    Member

    A big question is ( sorry if I missed it ) what kind of paint are you putting on?
    Color? Single stage? Urethane or laquer? enamel?
    base clear? metallic? pearl? transparent yellow pearl base clear or single stage white?
    Huge differences on what you really need to do.
    And your technique on sanding makes a difference on what grit to finish in etc.
    have fun
    wil
    www.sakowskimotors.com
     
  17. 49ratfink
    Joined: Feb 8, 2004
    Posts: 18,057

    49ratfink
    Member
    from California

    if you want to dry sand you just need to keep the paper clean. stop and blow all the buildup off once in a while. for what might not come off with that keep a clean new wire brush handy.
     
  18. oldskew
    Joined: Oct 4, 2009
    Posts: 24

    oldskew
    Member
    from idaho

    like everyone else said least of 400 if your going to seal after, but you can skip the seal stage if you want and sand it with 600 grit....as said ANY repair spots showing through primer need to be spot primered and feather edged....i would do 3 coats of primer block each coat on the final coat block to 400 seal and paint
     
  19. czuch
    Joined: Sep 23, 2008
    Posts: 2,688

    czuch
    Member
    from vail az

    Krylon.
    But I'm a loser.
    I'm a loser with a p.o.s. and krylon.
    Lets see pics. Its gonna be beautiful.
    unlike mine,with krylon.
     
  20. SlowandLow63
    Joined: Sep 18, 2004
    Posts: 5,953

    SlowandLow63
    Member
    from Central NJ

    Guide coat it, 320 wet, sealer, topcoat. If its a metallic go 400. Any finer and you lose a bit of the mechanical adhesion.
     
  21. FIFTY2
    Joined: Apr 9, 2008
    Posts: 340

    FIFTY2
    Member

    im gonna do a bc/cc

    proly a copper metallic with a flattened clear

    thanks for all the replies !!

    ill post pics when im done (if it ever stops raining)
     
  22. HotRodBen1987
    Joined: Jul 29, 2009
    Posts: 691

    HotRodBen1987
    BANNED

    Good luck and like everyone else said go with 400 or finer wet.
     

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