[Spray Enamel] How much to sand color before clear?

Discussion in 'Tech-Talk' started by Yonatan, Sep 27, 2020.

  1. Ray Stankewitz

    Ray Stankewitz Squier-Meister Platinum Supporting Member

    Age:
    63
    460
    Oct 11, 2014
    Central Indiana
    I would not sand "enamel" until it was rock-hard, totally cured. After a day or two, enamel seems cured but that's only on the surface. Enamel cures from the surface down. It will continue to cure for a month or more despite what it says on the can. It has to be cured enough that your fingernail can't leave a dent in the paint.

    I've been to Dupont's refinishing school years ago when they were still called Dupont. Lacquer takes a while to cure fully but so does enamel. As a rule of thumb, enamel is softer than lacquer when cured and you have to use the matching clear just to avoid possible interaction between color and clear. Lacquer is less fussy about clearcoats whereas some enamels (Painters Touch) will freak out when topcoated with good clear such as ClearMaxx 2K. That came from experience and an expensive lesson learned. Can you say "Alligator Paint?"
     
  2. Uncle Joe

    Uncle Joe Squier-holic

    Age:
    57
    Dec 18, 2015
    Jersey
    Hmmm. If the test for suitability for sanding is finger nail depression, mine passes with flying colors. It is a solvent-heavy automotive grade spray paint, so maybe that's the contributing factor. I don't have an SDS and I don't understand retail paint nomenclature very well (even though I've been in the pigment business for over 25 years), but epoxy, urethane, poly coat, whatever the coating, I think no matter what the marketing team calls the stuff a composition by weight percentage would be nice to have in order to better understand what we're dealing with here.

    That or I could just try to sink my fingernail in again.
     
  3. Ray Stankewitz

    Ray Stankewitz Squier-Meister Platinum Supporting Member

    Age:
    63
    460
    Oct 11, 2014
    Central Indiana
    Automotive grade paint is usually solvent-heavy. Stuff like Painters Touch and Krylon Fusion are typically not that heavy on the carrier. That's because the Gummint doesn't think we can handle good paint.

    800 grit is not outside the realm of havng the clear coat stick., as long as you have used an automotive degreaser to get your grubby skin oil off of the body before shooting color or clear. Just make sure the first and second coats are mist coats to help things get tacky.
     
  4. metalmerchant

    metalmerchant Squier-Meister

    387
    Mar 25, 2011
    cornwall UK
    Yup, I'll go with that. A dust coat also helps you to see where you're going when you apply your wet coat.
     
  5. nmagi

    nmagi Squier Talker

    Age:
    38
    96
    Apr 2, 2020
    Athens
    5 even 15 dry coats or mist coats as Ray suggests wouldn't be bad at all. But now your paint coat is smooth, I think your best bet would be to give it another coat or two of paint first. I am really not much of a painter but that is what I would do in my experience
     
    Angry Possum likes this.
  6. beagle

    beagle Squier-Nut

    907
    Nov 19, 2017
    Yorkshire
    Mist coats of enamel aren't good. Unlike nitro, they don't melt in, they sit on top of each other. When you sand back, each coat you sand through leaves an edge and witness lines.
     
    nmagi likes this.
  7. nmagi

    nmagi Squier Talker

    Age:
    38
    96
    Apr 2, 2020
    Athens
    Maybe, the truth is I only have used acrylic till now, but works more than fine on it too. Actually I just put some new decals after I ruined the stock ones trying some finishing thingies, I had some hard time with the front one trying to cover the decal edges and the seller advised me of 15-20 "dust coats" (I only knew of wet and dry ones lol, hopefully the same thing with mist ). Did hardly ten, fortunately the acrylic dust coats dried almost instantly. Back decal is better than original now :D
     
    Last edited: Oct 11, 2020
    beagle and dbrian66 like this.
  8. beagle

    beagle Squier-Nut

    907
    Nov 19, 2017
    Yorkshire
    There are many different acrylics too, those used in automotive paints are different to those sold for use in the home or by artists.
     
  9. nmagi

    nmagi Squier Talker

    Age:
    38
    96
    Apr 2, 2020
    Athens
    Anyhow the effect of many dry coats I noticed, off an acrylic rattle can, was that of a fuller satin layer, two or three coats were much harsher, like "fat" dust, obviously due to the fact you describe about nitro vs others, but every coat seemed like *filling previous gaps. At the end it seemd like a #1000-1500 sandpaper surface and wet coats brought it to a mirror shine
     
    dbrian66 likes this.
  10. beagle

    beagle Squier-Nut

    907
    Nov 19, 2017
    Yorkshire
    This one is auto-acrylic

    Geddes.png
     
    nmagi likes this.
  11. nmagi

    nmagi Squier Talker

    Age:
    38
    96
    Apr 2, 2020
    Athens
    Post your diet too please :) (*came back to note I 'm on a diet for like a 10th time in late years, but this time I 'm in really serious! -I hope. I "envy" thin people and didnt't mean anything ironic! and hope it didn't sound like that. So Thanks for the image you put up! I can also note the perfect positioning of your hands, specially the left :) )
    I would go for a full paint only in my dreams :)
     
    Last edited: Oct 11, 2020
    Yonatan and dbrian66 like this.
  12. Yonatan

    Yonatan Squier Talker

    Age:
    49
    23
    Jul 21, 2020
    Israel
    I think it was clear that you were being sincere :)

    Anyway, looks like I'll need to respray, or at least do a touch up! This body is resting precariously in my workroom and got scratched by me moving something around. I was mostly able to sand the scratch out, and should have quit while I was ahead, but I went for perfection and got a sand through! I would have done a touch up on the spot, but I didn't have any more of the Rust-Oleum Ocean Mist and had to wait until I had a legitimate reason to venture out (we're on complete lockdown here) to get another can. So maybe I'll just scruff sand and respray the whole thing.

    Now, on another and somewhat contradictory note, I'm seriously considering a color change: The Minwax water based wipe on poly that I had such high hopes for is shifting the Ocean Mist to a greener color on scrap. I thought that water based poly wasn't supposed to yellow! I also have Rust-Oleum 2x Gloss which is completely transparent over this color on scrap, but it is still a bit soft after a good two months, I'm concerned about whether it will ever really harden up enough to provide scratch resistance. I don't have access to (nor do I want to deal with the hazards of) anything like 2k, don't think I can get automotive lacquer in aerosol can format here, etc.

    sand through.jpeg
     
    Last edited: Oct 11, 2020
    dbrian66, nmagi and beagle like this.
  13. beagle

    beagle Squier-Nut

    907
    Nov 19, 2017
    Yorkshire
    The standard Yorkshire diet of eat all, sup all, pay nowt. ;)
     
    Yonatan, dbrian66 and nmagi like this.
  14. beagle

    beagle Squier-Nut

    907
    Nov 19, 2017
    Yorkshire
    It may never harden enough, as I said earlier. The acrylic I used still isn't as hard in some places as I would like after 12 18 months.
     
    dbrian66 likes this.
  15. nmagi

    nmagi Squier Talker

    Age:
    38
    96
    Apr 2, 2020
    Athens
    Hey, writings might give rise to misconception some times!
    I am not THAT fat, about 102kg, I would be happy with 92 though
    :D

    I thought of acrylic softness too, though on cars doesn't seem so soft at all. Luckily the sun is still hot in here, but I let the neck i finished close to an electric radiator for the rest of the day too. Didn't try the nail test yet, but I gave space for time to tell. :D Neck took me four days to top coat 5-6 coats )apart from the dry ones) and I think I rushed
     
    beagle and dbrian66 like this.
  16. Ray Stankewitz

    Ray Stankewitz Squier-Meister Platinum Supporting Member

    Age:
    63
    460
    Oct 11, 2014
    Central Indiana
    Okay, do not put ANY automotive clear over Rustoleum, unless you're good with alligator hide finishes. And, I don't remember the Rustoleum clear taking forever to cure and harden last time I used it. Minwax wipe on poly is not a good candidate for a clear top coat either. I would recommend you stick with Rustoleum but don't be in a hurry to assemble the guitar until the clear is hard and cured.

    Apply the Rustoleum clear with first a mist coat, wait a few minutes, then one wet coat. Allow that to cure a few days, then apply another wet coat, allow that to cure. Four to six wet coats should give you enough to cut and buff once it's finger nail test hard. Don't do infinite mist/dry coats, unless you like sanding forever to even out an orange-peel surface or possibly face an adhesion problem. Also, keep steel wool away from guitar finishes. Furniture, okay. Car chrome, good to go. Enamel paint? No Bueno.

    It's my $0.02 USD opinion that two months seems like a long time for clear to cure but maybe Rustoleum has altered the formula to stay within the Air Resources Board regulations. ARB and CARB, California's version, are forcing paints toward water-borne solutions, leaving guitar painters to source from StewMac, Mohawk (formerly Behlen) and Reranch (major players) for finishing supplies. So far, hobbyists, guitar and furniture makers still legally have nitro available to them or they can use automotive acrylic lacquer. Hopefully, we can still use these materials far into the future without being made illegal. As an aside, water-borne lacquer is available, too. I haven't used any (yet) but it does sound promising.
     
    nmagi and Yonatan like this.
  17. beagle

    beagle Squier-Nut

    907
    Nov 19, 2017
    Yorkshire
    I don't think anything we get over here has the same formulation as in the US, not for sale to the general public anyway. Cars are painted with something that is baked. Touch up paints haven't been nitro since the 1970s.
     
    dbrian66 and nmagi like this.
  18. nmagi

    nmagi Squier Talker

    Age:
    38
    96
    Apr 2, 2020
    Athens
    Yes, afaik that should be 1K polyurethane , I searched the hell of the country here for a rattle can but had no luck. Then next bet was acrylic
    I thought of those shops that pack rattle cans to your flavor but then got bored :)

    *You moved me to do a little re-search, if I have a good perception about this article
    http://compressors.matteicomp.com/blog/what-is-low-bake-auto-paint
    that low bake paint sounds like a 2k. 1k needs more heat than the 100 Celsius it mentions
    Should still be poly, I mean I can't handle a second mistake... lol. No, actually I m lost
     
    Last edited: Oct 12, 2020
  19. beagle

    beagle Squier-Nut

    907
    Nov 19, 2017
    Yorkshire
    On the whole, the best finish you're going to get on a guitar is the poly one it comes with. I only refinished mine because the guitar has great sentimental value. Any other guitar would have just got a body transplant from a donor.
     
  20. Yonatan

    Yonatan Squier Talker

    Age:
    49
    23
    Jul 21, 2020
    Israel
    Thanks for the application tips for the 2x Clear, maybe I'll reconsider it, but just wondering why you don't recommend Minwax WOP? The water based that I tried on scrap was easy to apply and hardened up very nicely. The only drawback I had was it's yellowing effect (despite the water based version not supposed to be doing that), but if used over the right color coat don't think that would be an issue
     
    Last edited: Oct 12, 2020