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  • Too much catalyst

    What happens if you use too much catalyst when preparing some urethane paint? How does the paint react? How does it spray? Flow out?

  • #2
    Discard the paint.
    A small amount over is OK, but o/w the results are unpredictable. At the very least you are gonna get solvent pop, then you get to do the whole job over again

    The paint chemists have the ratios all worked out

    If you are trying to get the paint to cure faster, use accelerator. Keep in mind that beyond a tiny bit of accelerator, it can slightly affect the shine of the paint.

    Too much accelerator will cause solvent pop, also. We only use it in cold temps, like from 50-60. Typically you want to shoot from 70-90. We will shoot down to 50 because we kinda know just how much accelerator we can get away with.

    Over 90 and you may end up with pop, also.
    They also make retarder. While we have it, we seldom use it. We try hard not to shoot over 90. The higher the ambient the more flash time you must allow, more than the basic instruction sheet says
    Last edited by tbirdtbird; 09-19-2018, 01:16 PM.

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    • #3
      Only use the mixing cups the paint supplier have. The cups are marked with all of the ratios i.e. 3-1-1, 3-1-1, 2-1-1 etc.

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      • #4
        I haven't mixed any paint, and when I do, I will follow the manufacturer's instructions.

        The reason for the question is that I have suspicion that my tank paint job was done with 2x catalyst. The Omni paint that I took them is mixed at an 8-1-1 ratio. I took a quart of paint, a 1/4 pint of catalyst and a quart of reducer. Now, it looks like I have about 1/2 of the catalyst left, but about 3/4 of the paint!

        The paint job came out o.k. Where they sanded/polished it is nice. Where they didn't, there is a lot of orange peel needing sanding and then polish. I was a bit surprised that the orange peel was as bad as it was, I figured it would be a lot smoother than what I found. I am still trying to understand what I am seeing.

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        • #5
          peel can be a lot of things, paint too thick, not enough reducer, air pressure too low, gun not atomizing well, skill level, etc
          adding catalyst tends to actually make the paint thinner
          Can you post a pic?

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          • BillLee/Chandler, TX
            BillLee/Chandler, TX commented
            Editing a comment
            No, too late for a picture, I've already done a whole bunch of color sanding.

          • H. L. Chauvin
            H. L. Chauvin commented
            Editing a comment
            Hi Dave,

            Your taking valuable time to report very detailed information on today's modern paint, catalyst, accelerators, temperature, chemicals in a shop, paint guns, and detailed painting procedures I'm sure is appreciated by many.

            So many different auto paint products and procedures mentioned on various auto Forums over the past years.

            Just wanted to say thanks for sharing your successful experiences.

          • BillLee/Chandler, TX
            BillLee/Chandler, TX commented
            Editing a comment
            I couldn't agree more, H.L.!! Thanks, Dave.

        • #6
          Hmmm, I think Brent is onto something...
          https://ppgrefinish-na.uberflip.com/...ct-catalog/13?

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          • #7
            Pulled my "Product Information"sheets out of file. Omni MTK Acrylic Urethane standard ratio 4:1:1 (MKT:Reducer:Hardener)
            Omni MAE Acrylic Enamel with hardener standard ratio 8:1:1 (MAE:Reducer:Hardener)

            These sheets should be available online. kenp

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          • #8
            O.k., a couple of mistakes on my part. This is not urethane, but is acrylic enamel with hardener. Here are pictures of what I bought:
            IMG_20180919_185957.jpg
            IMG_20180919_190144.jpg
            Here is the Product information sheet:
            OB16 MAE.MH101 Acrylic Enamel.pdf

            Note that this is Omni MAE #1 and that the mix ratio is, indeed, 8:1

            I opened the 4oz can of hardener and it is 2/3rds gone. I popped the top of the quart of paint and it is down about 1/4. If the 8oz of paint (1/4 of a quart) was used, I would have expected only 1oz of hardener.

            I have to add some paint where the "professional" job was lacking. I will use the 8:1:1 as the Product information sheet says.

            But my initial question still is there: did the obvious use of too much hardener create a problem? Orange peel? Etc.?
            Last edited by BillLee/Chandler, TX; 09-19-2018, 08:06 PM.

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            • Beauford
              Beauford commented
              Editing a comment
              yeah, not enough reducer . Humidity, swing all have a play along with gun. Some shoot flatter than others.

            • tbirdtbird
              tbirdtbird commented
              Editing a comment
              You are gonna get orange peel no matter what. I seriously doubt too much activator caused the problem. The trick for a pro is to minimize the peel, and there many many tricks to accomplish that.
              For example, we don't employ reducer in the first two coats. When we shoot the third coat we do add some reducer to help things flatten out. There are waay more tricks than that.
              Brent covered the desirability of minimizing peel in order to minimize color sanding. It was a small job, maybe they gave it to a novice painter.
              They may have 'borrowed' some of your hardener for another job, too, you'll never know
              Last edited by tbirdtbird; 09-19-2018, 10:04 PM.

          • #9
            I knew a Painter that surely must have taken a Teaspoon of Retarder, every Morning!!!!-----I "wonder" what would happen if sumbody switched it to ACCELERATOR?---I "hurd" that he puts 6 drops of Lacquer Thinner in his COFFEE, at break time.---Hope everyone stands back, when he lights his CIGAR!!!---BUT, strangely enough, he's a GREAT Painter!!!
            In my 35 year Mechanic Career, I've known & worked with some of the most STRANGE/COLORFUL/UNUSUAL Men you could even imagine. AND, I learned SO MUCH from each of them. WHY isn't everyone "NORMAL" like me????
            Dad Amazed!

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            • #10
              How long did you wait for the acry. enamel to cure before color sanding, etc. ?

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              • tbirdtbird
                tbirdtbird commented
                Editing a comment
                At least a week, even with hardener that product cures slowly

            • #11
              Extra hardner will cause excessive orange peel, but it is minimum. Like someone else said, they probably gave the gun to a novice painter, or if it was a collision shop one of two things probably happened. In collision shops, you match texture of paint. You don’t want the new panel to be slicker than the rest of the car. So you spray with the intent of getting orange peel. Possibly the painter is use to this and sprayed it that way on purpose. But the painter also may not have been use to the material, most painters these days do not use a single stage, and a lot never have. With single stage you spray it out as wet and slick as possible without running it from the very beginning, and it’s a hell of a lot thicker than base coat. This painter may have sprayed the color like he was spraying base coat and couldn’t figure out how to get it to lay down. Just my two cents. Lots of variables including tip size in the gun. Either way, a little orange peel is very easy to take care of. Hit it with some 2000 wet sand it smooth and buff it out.

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              • #12
                I knew a Guy that had a Cadillac re-painted & paid "extra" to have it done in ORANGE PEEL, like the NEWER CARS!!!
                Dad LAFFIN'

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                • #13
                  Just as a follow-up .....

                  I used the DiVilbiss Finishline paint gun that I had shown to Dave a week or so ago.

                  I mixed the MAE acrylic enamel as per the manufacturer: 8:1:1 (I did add just a bit more reducer, ended up 8:1 and then 1-1/4 parts reducer.)

                  I sprayed my gas tank where I had been dissatisfied with the "professional" job.

                  I will say without a doubt that the paint I applied was done far better! It flowed out nicely and had very little orange peel. The paint from the shop was very rough and lots of peel. I left an area where the chrome dashboard will cover as it was just for my own comparison.

                  Given the fact that most (2/3rds) of the hardener was used by the original painter, where it should have only been 1/4th, I suspect that the extra hardener caused the paint to catalyze too quickly and did not let it flow properly.

                  I am happy that I have had some personal success and I have learned a LOT! Thanks to all,Dave, Logan, Brent, ......
                  Last edited by BillLee/Chandler, TX; 09-23-2018, 08:40 PM.

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                  • #14
                    Glad it worked out.
                    Last edited by tbirdtbird; 09-26-2018, 05:54 AM.

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                    • Tom Wesenberg
                      Tom Wesenberg commented
                      Editing a comment
                      Yep, beside the dissatisfaction of the "pro", I can't afford them, so I learn and do my own work.

                    • BillLee/Chandler, TX
                      BillLee/Chandler, TX commented
                      Editing a comment
                      Couldn't agree more, Tom! I am now sufficiently confident to try more. I have a whole panel on my car that was never painted properly (the area above the beltline, surrounding the rear window, up to the top vinyl) and I will attack it this fall. Right now I just need to get the car back on the road!

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