[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

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    If you plan to go that route, poly over a new color, get a test piece done to see if the poly does darken with some age. I think you will find Wipe-On Poly will discolor most enamels quite quickly and that's why I don't recommend it. Depending on the pigment in the base color, it goes yellow or brownish in short order. For whatever reason it will not discolor plastic/celluloid binding or rosettes and I'm sure the formulation was meant for bare wood or sealed/grain filled acoustic guitars. It works quite well, cures nice and hard but it needs about twelve or more coats to get enough finish to cut and buff. It will cut and buff to an amazing finish, though. the poly also seems to lift water based dyes so it can't go over a dye burst, either. I'm not sure about it affecting alcohol-based dyes.

    I assembled and finished a Hosco(?) brand parlor guitar for a friend some three or so years ago. I used the wipe-on due to no spray booth availability at the time. It was amazing to look at and because a number of glitches were caught before assembly, it plays just as nice as it looks. I need to find a pic of it for reference. I wet cut to 2000 grit, used Meguiars "Tan Bottle" fine cut, followed by swirl remover then show car glaze on it, all by hand.
     
  2. Ray Stankewitz

    Ray Stankewitz Squier-Meister Platinum Supporting Member

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    Most automotive paint on either side of the pond is a 2K Urethane or Polyurethane based Enamel. The hardeners contain Isocyanoacrylate (bad stuff!) as a catalyst ingredient. Baking just speeds the cure rate and allows you to use less hardener. The actual cure is the cross linking of the paint molecules. BTW, those 2k paints will not cure hard without hardener to start the cross linking. when I worked at an amusement park as a rides tech, we painted DuPont Centari 5000 2K outdoors, even in the winter. It cured just fine overnight with no heat. I'm sure ICI Auto Autocolor (UK) is also 2K Poly or Urethane.

    Automotive touchup paint (Duplicolor is a major US player, also PaintScratch) in spray or bottle are acrylic lacquer. It has to be something that cures fast, so acrylic lacquer fills that bill. Nitrocellulose lacquers are only available from a very limited number of suppliers and don't ask for this stuff to be shipped to The Peoples Republik Of Kalifornistan! Lil Daddy Roth/Roth Metal Flake (custom automotive paint) is based in my old home town of Fremont, California and at the time he couldn't ship to anywhere in Cali due to CARB regulations. I did buy some SprayMaxx 2K right from his local shop and he was happy to sell it to me, right across the street from the Tesla plant.

    I hopes this makes some sense. If it doesn't, I'm sorry because I haven't had enough coffee today; the Cuisinart coffee grinder lost its battle with old age and overuse this morning. Made some very nasty noises and gave out a small puff of magic smoke before signing off. didn't even have the decency to give me enough to make a pot of mud before waving the white flag.
     
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  3. Yonatan

    Yonatan Squier Talker

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    Sorry to hear! Also, I don't know what is in play here, but just after I read this I went down to make some coffee, and I somehow spilled boiling coffee grounds and coffee all over our kitchen cabinets!
     
  4. Yonatan

    Yonatan Squier Talker

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    As much as I really liked the RustOleum Ocean Mist, I realized that I didn't have a clear coat strategy for it, with the Minwax water based wipe on poly making it greener, and with me not fully trusting the durability of the RustOleum 2x Clear.

    So I tried (on a piece of scrap) the wipe on poly over a darker color of RustOleum that I had, and it came out perfectly!

    So after scuff sanding the body, wiping down with naphtha, and three coats about 10 minutes apart, here is the new look!

    There is one spot where this can splurted on me, I've seen that as a common complaint but it never happened to me before, hope it will sand out.

    colorchange_edited.jpeg
     
    Last edited: Oct 17, 2020
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  5. Yonatan

    Yonatan Squier Talker

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    I wasn't bonding with the blue, it looks great in the picture above, but in person it was a brighter hue.

    So it's back to the Ocean Mist!

    I'm not sure I remember at this point the entire finish history, I think I have it written down up until just before the blue :)

    oceamymistagain_edited.jpeg
     
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  6. Yonatan

    Yonatan Squier Talker

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    Of course it means that I'm setting myself up for the RustOleum clear (the poly yellows it).

    So I guess that will be the plan!
     
  7. Ray Stankewitz

    Ray Stankewitz Squier-Meister Platinum Supporting Member

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    One of the problems with doing a clear coat, even if it's from the same manufacturer, is the fact the clear always changes the color to some degree. Most of the time, it's not much of a change. Sometimes, it's a major change.

    This is the reason it is suggested to do a test spray-out on some wood that's been prepared just like the body you intend to shoot. I.E. it's been sanded, sealed, grain filled, primed just like the body. This will tell you if it will or will not work out.

    Another tip; warm your spray cans in hot water. This will actually thin the paint a bit, making it spray out better. A side benefit is the heat will boost the pressure in the can, assisting in a good clean spray-out. The cans don't have to be too hot, just a nice warm temp. If it's too hot to hold, it's too hot. Got it?
     
  8. Yonatan

    Yonatan Squier Talker

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    I've already prototyped it on cutoffs from building the body, the Rust-Oleum 2x Gloss Clear is truly crystal clear over the Ocean Mist color! My only concern is about its durability. Will try your application suggestions. Thanks again for all the tips. I have a scrap with the Gloss Clear from about 3 months ago. It is still hardening, almost scratch resistant at this point, but not quite. I don't mind if it takes 6 months, I'm just concerned because some people say that it never really hardens up, even after 1 year. (I can't get 2k clear nor would I want to deal with the dangers of it).
     
    Last edited: Oct 23, 2020
  9. Ray Stankewitz

    Ray Stankewitz Squier-Meister Platinum Supporting Member

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    Good to hear your test sprayout was a success with no change in color. Usually, a color is not affected much or possibly not at all but there are those times a color really changes under a clearcoat. One that comes to mind is Fender Fiesta Red. It's an orange-red that looks lighter when it's just cut and buffed, no clear. The clear deepens it a bit and adds a highlight to the color. Another color is Reranch Coral. It mimics Fiesta Red that's faded over the years. It looks like two different colors, depending on whether or not it's topcoated.

    My brother and I painted his motorcycle about fourteen years ago with Rustoleum Painters Touch spray bombs. It hardened just fine after a few weeks to cure the clear. The key is to put on light coats and follow a schedule as I put forth in a previous post. The schedule allows time for the coats to out-gas and begin curing. Out of curiosity, how did you spray the test piece with the Gloss? Was it heavy, wet coats or light, "just glossy" coats?

    That infamous SrayMaxx @k not withstanding, applying clear coats is a finicky deal regardless to material. Each spray day of that schedule has that first initial coat, then a final coat for that day that's "Just Glossy" and not too heavy. Does that make sense? I like to back away from the piece just a bit farther than normal and take my time getting that "Just Glossy" layout to the material.
     
  10. Yonatan

    Yonatan Squier Talker

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    Interesting point, since it was just a test, I was fairly indiscriminate, it was something like three heavy coats (sprayed at close range) several minutes apart, so basically the opposite of what you described.
     
  11. nmagi

    nmagi Squier Talker

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    I 'm curious, is rustoleum a polyurethane or what?
     
  12. Nduro

    Nduro Squier Talker

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    [QUOTE = "beagle, post: 987572, member: 12616"] Uważam, że żadna z farb w sklepie ze sprzętem nie stwardniała na tyle, aby można ją było używać na gitarach. [/ QUOTE]

    I use spray brake calliper paints, they are on hard synthetic resins and such paint is very durable. I do not give a colorless varnish, I only polish the base paint with a paste.
     
  13. Nduro

    Nduro Squier Talker

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    I use spray brake calliper paints, they are on hard synthetic resins and such paint is very durable. I do not give a colorless varnish, I only polish the base paint with a paste.[/QUOTE]
     
  14. Ray Stankewitz

    Ray Stankewitz Squier-Meister Platinum Supporting Member

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    Rustoleum is a type of an acrylic enamel unless you have a can of their black lacquer. If so, it will say lacquer on the front of the can.
     
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  15. nmagi

    nmagi Squier Talker

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    I see, thank you!
    I have noticed some rattle cans with such a label, but also noticed that most of the products don't mention the ingredients, except maybe the main one, if at all, so I had to search for the SDS documents.
    I live in an apartment so had to go with a can, but not all provided a SDS. I was searching mainly for a polyurethane rattle can, but couldn't find any, then on "acrylic" cans I got a headache finding an acrylic/poly too. Heard about people going with Rustoleum and Duplicolor , rustoleum has just a couple of products available in Greece and Duplicolor was marked plain acrylic (mystic recipe lol) , so I just went buying a cheap "acrylic" car paint can I found in a local store, which also had some good recommendations here, and by now, after a couple of weeks I tried scratching the surface I am very pleased with the results, dried pretty hard.
    I guess when not a pro with all the tools, you get that pain, but seems i was lucky :)
     
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