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when doing multiple PC coats.....

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  • when doing multiple PC coats.....

    what, physically happens with the "first" coat in a multi-coat project? my understanding thus far, for multi-coats is: 1) prep, powder and bake the first coat 2) powder and bake the second coat 3) powder (usually "clear") and bake the third coat.

    my questions are:
    A) do you let the object cool all the way to ambient BEFORE the second and/or third coats?

    B) my understanding from others tells me that once that first coat cures, that it might negate getting a good positive-to-negative charge going? is this so? you know.... like the PC might insulate the object from electrical current?

    C) what physically happens to the first coat when subject to ANOTHER session of 350-400 degree heat cycle? does it "melt"? does it seep up through the subsequent coats? (i.e. a white base coat under a florescent 2nd coat) and does putting a clear final coat in anyway diminish the surface finish of the PC under it?

    D) one pro-PCer in my town says he actually sands with 1500 "between coats" sometimes. is this possible/true??

    E) what is the "best" way to clean the gun between colors?

    thanks for bearing with all these newbie Qs!!

  • #2
    I've re-coated parts with a 2nd coat of the base color right out of the oven because the first coat didn't cover well. I've also sprayed clear on a still-hot base coat.

    If the part is still hot, the powder will melt as soon as it hits the part with or without the static charge.

    I change colors by:
    1) removing the cup and emptying it out.
    2) using compressed air to blow out all the residue powder from the gun and cup.

    If more needs to be done, I'd like to know as well...


    • #3
      I always use a blow hard to fully clean the gun. That in my opinion is the best way to get it fully clean. Other wise you could end up with colors mixing together. Metalics are the hardest to clean out the gun.


      • #4
        my gun has a secodary air adjustment on the barrel and I pull it out and clean the threads the powder seems to collect there..
        Pro-Tech Powder Coating
        93976 Ocean Way
        [email protected]
        Gold Beach,Oregon


        • #5
          I found it was harder to get an even 2nd coat on awkward parts that were still hot. So I let them completely cool, and that seems to work great. I still get a fine static charge and it coats really evenly...

          I don't do any prep, just let it cool, spray again, and rebake, no issues.

          As for cleaning the gun, I always just use compressed air, and totally overdo it. I got a bit of red contamination while spraying yellow, and it was not an appreciated effect.