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Baked on Enamal Spray Paint

Discussion in 'METAL FINISHING, CUTTING & WORKING' started by RandyM, Sep 9, 2013.

  1. RandyM

    RandyM United States Global Moderator Staff Member H-M Supporter-Premium

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    I just had an interesting experiment on a bracket I was making. Last weekend I painted it and left it to dry all week. Well, I went to mounting it and found that it was still very soft and sticky. The paint was enamal from a spray can (fresh can). After not wanting to wait any longer on "if" it would dry, I fired up the powder coating oven and baked it. Not ever trying this before I was unsure as to my results. I mean what temp and time do I use? I figured it didn't really matter as I was probably going to have to re-coat it anyway. So, after slowly turning the heat up to 200 degrees and baking it for about 3 hours I let it cool and removed it from the oven. The reason I baked it so long is that the paint stayed soft as long as it was hot, which I was not expecting. I then figured that it might harden up once it cooled down. Yup, that is exactly what happened. So, long story short, everything turned out perfectly and I was able to finish the project. Has anyone else experimented with baking paint? Please let me know how it turned out for you. I may do more of this in the future just to speed things up.
     
  2. astjp2

    astjp2 United States Active User Active Member

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    My work bakes all of their painted parts at 140* for an hour or two depending on what the part is. We use epoxy, eurothane and water based paints. Tim
     
  3. pjf134

    pjf134 United States Active User Active Member

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    Some body shops use curing heat lamps after a paint job and has been done for years. A old auto paint guy told me a long time ago to use cold water on a Enamal job after a day or two to harden the paint, but no hard stream or rough wiping. A uncle of mine back in the 60's worked as a painter in a shop that painted metal office stuff and baked it afterwards. I wonder if this would work on rustolium oil base paint? I will have to try this, thanks for reminding me of this.
    Paul
     
  4. RandyM

    RandyM United States Global Moderator Staff Member H-M Supporter-Premium

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    So Paul, did you try the cold water trick? I am having a hard time understanding how it would actually work. Yeah, try it on Rust-Oleum and report back. My guess is, it will work pretty well. I had a hard time finding anything technical on the web. Looks like a lot of experimenters on other forums, but nothing from any of the manufactures on baking.
     
  5. Ed T

    Ed T United States Active User Active Member

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    I have had very good luck baking solvent based paint especially enamels which can take a long time to harden up. It is particularly useful on wrinkle enamel which, once you figure out how to make it wrinkle, still takes forever to get hard enough to handle. Enamels "dry" in two stages, the first is the evaporation of the solvents and the second is the polymerization of the oils in the paint. Generally, the solvent evaporation does not take too long depending on how much paint was applied, but the polymerization can take weeks or longer to complete. I remember reading that old auto enamels could take months before they were hard enough to wet sand or polish. Anyhow, baking accelerates the polymerization process and really helps to make the finish harder sooner. If the paint is applied too heavily and there are solvents trapped in the paint film, you do run the risk of boiling the solvent embedded in the paint which produces a mess. I generally let the parts get dry to the touch and then put them in a cold oven and turn it on. It's a lab oven with a convection fan and heats pretty slowly and there are not any exposed heating elements, so there is no radiant heating like you might get in an ordinary kitchen oven. Radiant heating is a potential problem since the part can get way hotter from the radiant heat than from the air temperature in the oven. I generally run the oven a 200-250F. I set the timer for 3-4 hours and just let it heat up and cool down on its own. I have also found that getting the paint harder helps a lot with the removal of masking. If the paint is not hard, it tends to come off with the masking tape which is really annoying.
    You don't have to have an oven to bake the paint. I've used a cardboard box and an old, low wattage hair dryer on many occasions. You can also heat the parts other ways. I recently rebuilt an old lathe and some of the parts are just too big for my oven so, for example, I heated the pedestal base by arranging a heat gun to blow into it hich warmed the whole thing nicely and the paint was hard enough to proceed with the reassembly in less than a day. Needless to say, any of these alternatives require careful monitoring while in operation at least until you're sure the whole thing isn't going to catch fire or melt something.
    Baking works for me. Your milage may vary
     
  6. f350ca

    f350ca Canada Active User Active Member

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    I add automotive enamel hardener to any oil based paint such as Tremclad or Rustoleum. Dries in an hour or two and gives a harder and shinier finish.

    Greg
     
  7. rdhem2

    rdhem2 United States Active User H-M Supporter-Premium

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    Great information. I am about ready to try my first "REAL" paint job. A 1939 International Farmall "H". Never done more then rattle can before as I hate the mess and always get heavy handed because I am impatient with the whole procedure. My painter delivered his gun, said "About time you learn. Good project for it. Good luck", and left. What an attitude!
     
  8. RandyM

    RandyM United States Global Moderator Staff Member H-M Supporter-Premium

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    Now this is great stuff. Thanks guys.
     
  9. astjp2

    astjp2 United States Active User Active Member

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    Epoxies are normally thermal setting, IE they cure with heat. Heat lamps put off UV, so it can degrade the shine, oven temps need to be warm but not baking hot (140ish) not 250....Tim
     
  10. pjf134

    pjf134 United States Active User Active Member

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    Randy,
    I have tried the cold water trick and it seems to work on some test pieces that I did years ago. I will have to try hardener with Rustolium to see how that does. I do agree with the lower heat for the regular paint and I think that powdercoat takes higher heat because you have to melt the powder to get the finish. I have also cranked up the heat a little to warm the metal a bit before painting and seems to stick better. I do need to paint a steel man door before winter and was thinking what to use that will dry quick so I can put it back on the same day and car paint is a little costly. I did use some paint a long time ago from a hardware store but don't remember the name and it dried real quick because it rained as soon as I was done spraying it and no water marks at all on it and it is still on my neighbors trailer since the mid 70's and still looks good.
    Paul
     
  11. frbutts

    frbutts United States Active User Active Member

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    For years I have put all my paint projects out in a gentle rain after it is dry enough to not be sticky. It make the paint hard enough to handle after over night.
     
  12. bstarling

    bstarling United States Iron Registered Member

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    I used a heat gun on a shotgun barrel that I had painted with BBQ grill paint. It came out harder and tougher than woodpecker lips. Didn't bother to check the temperature of the barrel, but it was plenty warm.

    Bill
     
  13. yugami

    yugami United States Active User Active Member

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    How does one do this "cold water trick"? Just a little spray bottle or a a wet rag or what?
     
  14. terrywerm

    terrywerm New Member Liaison Staff Member H-M Supporter-Premium

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    I don't mean to go off topic here, but do not let yourself be intimidated by your first paint job. My first one turned out just fine, and now I don't buy rattle cans anymore except for really small projects. One thing that I can recommend is to get your red paint from CaseIH and get some hardener too - it is a bit more expensive but you will not be disappointed. Most of the other 'look alike' paints just don't look the same, nor do they hold up as well. My first is shown here:

    View attachment 60632

    Oh, ignore the date on the photo - I replaced the batteries in the camera and forgot to reset the date on the camera! The tractor was painted in April of 2004 and the photo above was taken in August of that same year after all of the assembly was completed.

    As for baking paint, I've been doing it for years. Small parts go in the kitchen oven at low temp for two or three hours, larger items get placed under heat lamps, usually surrounded by cardboard or similar to keep the heat in a bit better. I never tried the hair dryer trick, but don't see why it would not work. None of the parts on the Super C were baked though, I just used enamel hardener in the paint.
     
  15. jgedde

    jgedde United States Active User Active Member

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    As far as enamel paint and baking, it does make the paint cure faster. However, what you end up with is not baked enamel. The term baked enamel is used when talking about the baked ceramic (or porcelain) finish used on appliances and bathtubs.

    As far as the water treatment goes, it does work... Enamel dries by solvent evaporation and cures by oxidation (or cross-linking if a hardener is used). Water speeds oxidation. Just like with iron and rust.

    Heating the enamel helps dry the solvents and speeds the reaction time for curing. In some cases, if the humidity was too high when the paint was applied, or if it was applied too thickly, it may be weeks to get full cure. This is because the outer layer of paint is cured, but inside it's sealed off from the air. Solvents can't get out and oxygen can't get in. B

    Baking can help with this sometimes by allowing the solvents inside to escape... Why? The vapor pressure of the solvents is increased at high temperatures and the outer layer softens and the solvents can get out.

    Baking works well, but don't rush it. Heating the curing paint too soon can cause bubbling (solvent pop), loss of gloss, smoothness issues, etc.

    John
     
  16. Uncle Buck

    Uncle Buck Active Member Active Member

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    I generally avoid Rust-o-leum paint except for the hammered finish line because it seems to be the only brand I have had consistent problems with it not drying. I prefer most any other brand due to this problem.
     
  17. Privateer

    Privateer United States Active User Active Member

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    I don't see a photo :whistle:

    Terry
     
  18. terrywerm

    terrywerm New Member Liaison Staff Member H-M Supporter-Premium

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    Sorry about that. Some photos disappeared off of a bunch of posts a while back when they had to restore the forum due to the site being hacked. Here is the photo once again:

    100_0269.JPG

    Thanks for bringing it up!!

    100_0269.JPG
     
  19. donthack

    donthack United States Active User Active Member

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    e

    Replaced our electric oven with gas, set aside the oven for powder coating in the garage. Before I ran the power line 2 years later a single mom needed is more that me. Do you get by hardening paint in your house oven? Now using gas I don't want to cook paint in case of off gasses.
     
  20. terrywerm

    terrywerm New Member Liaison Staff Member H-M Supporter-Premium

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    I don't think one would have to worry too much about gasses from the paint as they would burn off slowly as they are produced. I don't think that the paint could produce enough gas fast enough to reach the LEL of those vapors. Not only that, it wouldn't matter if you used an electric oven or a gas oven, if the temps are high enough to ignite the gasses, it doesn't matter what the heat source is.
     

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