91 mustang , sprayed SPI epoxy as a sealer . let it dry about 2 hours. Applied 3 coats PPG Shopline plus basecoat ( titanium frost ) light silver .
I have sprayed a few metallics in the past . Med . coat, cross hatched 2nd coat. Immediately After last coat increased pressure a little , increased distance a little to fog ( even out metallics ) . Didnt dry spray it.
Temp in garage about 72-75. used DT870 med. reducer. Everything went well.
Let that dry 20 hrs , temp probably dropped to 55-60 in garage overnight.
Problem : Today I sprayed SPI Universal clear , I sprayed it wet like normal. I have a few mottling places on the hood, hatch and roof. None on the sides.
I called a friend of mine who owns a restoration shop, been painting 25 years. He said its possible the clear was put on so wet it moved ( shifted the metallics ) . He had a similar problem on a light silver last year .
His solution, let it dry for a couple of days.
Grey scotchbrite it, clean with wax and grease remover , apply more basecoat. Put 1st coat of clear on med. not wet . 2nd coat med. 3rd coat wet . He said this worked for him. If I had used a hardener in my basecoat would this have helped?
It sounded like your problem started at the final coat. I used to shoot PPG ALOT in the past. AN the problem is that when you are doing your final coat of metallic "evening". When you increase the distance...and air pressure...you are creating more overspray. This overspray will collect more on the top surfaces than on the sides. This depends on the air flow in the booth, spray equipment...and how "foggy" it got in the booth while doing you final coat..versus the previous coats.
I found that doing my metallic "evening" was done right after I shot the panel...so the misting would stick to wet basecoat...and not a coat that has flashed. And I would use a slower grade of reducer.
Letting it sit for 20 hours was fine...but I would have gone one grade slower in the reducer. This allows the mist to stay wetter longer and not be so dry. EVEN though you mentioned you didn't spray it dry...there was still overspray...that was floating around and collecting and NOT sticking. This is what "walked" on you when you applied the clearcoat. Been there many times...and I do not have these issues any more due to using another brand of paint...that does not have this problem...or at least I have figured out how not to have metallic disturbances any more.
I never put hardener in basecoat.
Wheree ver your clear is shiny...you paint will not adhere. Make sure that it is ALL DULL. I personally do not like to use scotchbrite in this case...because of the residue and lint given off by the scotchbrite while using it. It can cause for more trash in your clearcoat. I prefer to watersand with 500 grit wet.
Thanks for your help Dub. Since you do your metallic "evening" right after you shoot the panel , do you only increase the distance a little and not the pressure ? Since you would be changing pressure after every panel ?
Do you also agree with not putting your 1st coat of clear on real wet ?
Thanks for your help Dub. Since you do your metallic "evening" right after you shoot the panel , do you only increase the distance a little and not the pressure ? Since you would be changing pressure after every panel ?
Do you also agree with not putting your 1st coat of clear on real wet ?
Air pressure stays the same. I MAKE sure that my gun head is perpendicular to the panel at ALL times...so the metallicas lay flat. I increase the distance and do a slow travel speed across the panel...sometimes "criss-crossing" to help remove any metallic issues I may have.
One way I know that I have it right...at least in the system I use...I look across the panel and see if I have a dry dust forming...which usually does not occur. SOMETIMES...I even use my tack-rag and wipe the panel down CAREFULLY and see if I am collecting paint overspray on it. Usually...due to the reducer and the fact that the panel was still wet when I layed out my final metallic "evening" coat...my tack rag is clean when done wiping down the panel. I will only tack rag my final coat down before clearcoating if I notice specks of trash or lint....but I usually got those on the second coat...before I applied my final coat and metallic "evening" coat. But the trash/lint issues can be reduced with PROPER PREP, MASKING, PAINT SUITS, HEAD SOCKS and gloves .
I apply my first coat of clear with a medium wet coat. I DO NOT shoot it dry. I want enough of clear so I am getting the build I want in the end. I DO NOT FLOOD the first coat. I DO NOT use a clear that has a reducer in it. JUST clear and hardener. I can adjust the "flow" by changing the grade of hardener (slwo, medium, fast)...depending on the temperature and how much VOLUME I am applying when I pull the trigger. I NEVER have my gun set to FULL TRIGGER PULL. The fluid adjustment knob is there for a reason. With teh type of clear that I use. I turn my fluid adjustment knob all the way in so that ther is NO trigger pull....then I turn it out 2 to 2 1/2 FULL TURNS. And that is where it stays. It allows that volume of clear to be atomized with the air pressure I use to make the clear break up into small droplets and lay out slick...with very little orange-peel....even the sides of the car This is also depending on the size of the needle/nozzle in the gun also (1.3, 1.5,etc.). It is a balancing act to spray one out "slick as glass" and not having heavy orange-peel. It is like your handwriting and mine. WE both can write...but differently...Clearcoating is much the same way...you have to get your set-up to work with your style...and see if it works...if it does not...you need to change it. That is what tset panels are made for......PRACTICE.
"DUB"
I did notice I had what looked like dry dust ( overpsray ) on the panels before clearcoating . I guess that was the indication the reducer was too fast or I was dry spraying when trying to even out metallics .
I have sprayed silver metallics without this problem before , maybe I used a slower reducer . Need to keep notes I guess.
Trying not to get gun shy now. Thanks for your time and knowledge, sincerely appreciated.
If it occurs again...the dry dust issue....and you for some reason do not feel like "tacking" the car off...you can put a VERY light coat of clear on it to lock this stuff down. I have done this in teh past...and it does work but youo have to be really careful on how WET you get it so teh clear does not disturb what youa re trying to keep comttrol of.
Best rule is to watch what is going on and change reducers if you feel it is drying to fast...and you are getting dry edges...and the base is not melting in as it should be.
Do not get gun shy...you know what the problem is and it is easily repairable...the next time. It is a part of the "learning curve" that unfortunately...you had to learn the HARD WAY...like many of us. BUT quaranteed....you will never forget it...and may still run across issues that will teach you something else entirely different. I can write a book on my experiences....and it would be a "doozie".
I wetsanded the dust nibs with 600 grit using very little water, as not to disturb paper,tape etc.
Scotchbrited grey the rest. Blew the car off , wiped carefully with waterborne solvent. Let that dry, blew it off again. Used tack rag.
Applied 2 coats of base with a slow reducer. Temp was 72. It layed down nice, no dust overspray like I had the 1st time.Metallics were even, no mottling etc.
Never thought about using this slow of reducer in this temp 1st time.Let this dry about 3 hours then applied 1st of clear lightly, let it flash. 2nd coat a little wet, 3rd wet,4th wet.
Only problem two little bugs landed in hood of all places on 2nd coat. I used a dirt pic ( looks like a bugs sword )
to remove most of them, some small specks might be left.
Of course this didnt happen the 1st time spraying , always something to contend with I guess.
I think it will be fine after wet sand and buff. Thanks for everyones help, I never stop learning.
Corvette Store
Metallic shifted
