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Old 08-03-2005, 10:49 PM
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I did something wrong, color doesn't match

I've been working on this project car for a while now and i've been using kirker products from smartshoppers (gray - acrylic urethane). I spent a long time prepping the car and then block sanding the primer, everything looked good. i decided to paint the car in pieces just because i thought i would get better results. i painted the base coat on all the pieces (hood, fenders, and doors) one night and the rest of the car body the next. i waited a day and then started to wet sand the car body, everything was going ok (the paint didn't come out smooth, should i have added reducer to the base coat?). then i go to wet sand the pieces a few days later and notice that they're a different color (darker), they all recieved the same three coats and i noticed that if i kept sanding the darker pieces i would eventually get to lighter paint (it's not the primer, the primer is a dark gray). did i screw up by painting the body last and sanding it first and not give equal curing time to all the pieces before wet sanding? right now i'm planning on putting the car back together and spraying it all at once, but i would like to understand what i did wrong.

Also, i'd like to know the tricks for getting the paint to come out smooth. i spent a lot of time playing with my gun settings (HVLP) and it always ended up with serious orange peel or dry and dusty. i didn't use any reducer, should i have?

thanks in advance for any advice.

Paul

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Old 08-03-2005, 11:12 PM
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Color of paint can vary slightly depending on how its sprayed, and what the temperature was. This is expecially true of metallics. You didn't say what your color was. A metallic sprayed heavier or lower pressure will be darker (flake lays down more) then one sprayed at a higher pressure or dryer( flakes stand up). To be sure that the color matches it is usually best to spray all the same day, or make sure all your gun settings and application, same distance and speed of gun travel, and paint reduction are the same as well as shop conditions. I am confused on what you are saying by sanding the basecoat. Basecoat needs a clear over the top, and if you sand it more base has to be applied where you sanded. Most basecoats give around 24 hrs to apply clear or else it all has to be sanded and more base applied. If the basecoat is activated then this time is shorter. Then clearcoated. Are you talking about basecoat, which when sprayed drys dull. And yes all the basecoats I've used needed to be reduced, not all brands are reduced the same. Too little reduction is one cause of orange peel as well as the pressure and distance, and may also be a cause of the dryness. but if a true basecoat type paint it will dry somewhat dull.

Last edited by kenseth17; 08-03-2005 at 11:26 PM.
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Old 08-04-2005, 08:02 AM
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Paul, I'm guessing that you're using a single stage urethane. These can be really tough to spray if it's a metalic color, solids usually spray just fine. All of the singlestage urethanes I've ever sprayed needed a reducer and hardener. Color match can be tough with these unless you spray every exterior surface at the same time, spraying the car together would be your best bet if the bodystyle permits- Some of the 20's-40's cars need to be shot with the fenders and hood off. Once you get it all sanded apply a few more coats of properly mixed and reduced paint and it should be fine. More info as far as color, car model, apraygun model, etc. would get you more answers to your problems. Bob
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Old 08-04-2005, 10:20 AM
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thanks for the info guys.
the paint color is light gray (non metallic) and it is a single stage urethane. my gun is some off brand solf by my local auto paint place, they told that it would be a good one for my first couple cars and the price was right. i am using a 1.4 tip. the car is a first generation VW rabbit that i'm setting up for autocross and the occassional road course.
i'm going to do a bit of experimenting with some reducer tonight, the paint can says that a max of 10% reducer can be used, so i'll start with 5 and see how it goes. then i'll paint the whole car at once.
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Old 08-04-2005, 03:51 PM
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A dove type gray color is not affected by humidity or air pressure or how much reducer you put in it.

So that leaves the only option left is you did not mix the paint real good
before you poured it out of can and not uncommon for the white tint to settle as its the heaviest.

It only takes one bad mix to throw the whole rest of gallon off.
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Old 08-04-2005, 05:30 PM
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i use base clears, or bc/cc as its known its way easier to control and sand out imperfections. the base is just that enough coats to give the even color and then the clears make it all work. runs dips sags and orange peal can all be sanded out to a briliant shine... i would not even try a single stage cause of the difficulty in getting em smooth.

jeff
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Old 08-04-2005, 07:17 PM
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i could definately see how i could screw up the mixing and get different colors when i paint on different days. the part i still don't understand is how the paint can change color as i sand it (going from dark to light before hitting dark primer) on a part that was painted all at once. i suppose that the paint could have settled in the gun, but could it be that i didn't wait long enough in between coats and the paint settled on the car? i have been waiting the recommended 10-15 minutes between coats, but i could have lost track of time.
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Old 08-04-2005, 07:44 PM
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you could be sanding threw layers thus changing the color by thinning...
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Old 08-04-2005, 08:08 PM
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it's not a gradual change, it goes from a darker gray to a lighter gray suddenly.
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Old 08-06-2005, 07:58 PM
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You're experiencing floating/flooding. When you spray it out and its still wet the differences in pigments ie size, interactions.. are causing your darker pigments to float and your lighter ones sink. Generally due to low visc or low pvc. Are you thinning the hell out of it ? if not its a property of the paint, in some i've designed i used molecules that cling onto my black pigment to literally stop mobility when wet film.
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Old 08-06-2005, 09:20 PM
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Basically, single stage paints are really best used on trucks or cheap jobs that won't ever be buffed much. That and the likely lack of proper mixing have put you in the position of deciding to repaint the vehicle.
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Old 08-07-2005, 09:20 AM
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Quote:
Originally Posted by xshore
You're experiencing floating/flooding. When you spray it out and its still wet the differences in pigments ie size, interactions.. are causing your darker pigments to float and your lighter ones sink. Generally due to low visc or low pvc. Are you thinning the hell out of it ? if not its a property of the paint, in some i've designed i used molecules that cling onto my black pigment to literally stop mobility when wet film.
I was wondering if maybe this was what was happening, I've seen the same situation myself with light colored singlestage solids and figured that was the cause but wasn't absolutely sure-I'm not a paint engineer. You've provided good confirmation that the pigments can indeed settle at different rates and change the color. Just one more variable to deal with and consider before deciding whether or not to panel paint a vehicle I guess. Is this the same phenomenon that causes reds to darken as they dry? Solid reds can sure be a PITA to match because of the major shade changes from liquid state to fully dried. I've also been told most of the red pigments are supplied from India and the darkening deal is just common to those pigments. ???? Bob
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Old 08-07-2005, 10:18 AM
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TallPaul,

I think your issue is beyond my knowledge to comment but I will add something you should consider. Intermixing your paint containers is a good idea especially if you are spraying in segments. I always ask for an empty gallon and then pour all my containers back and fourth to get the same mix on all the cans. Usually my projects are restorations that are tore down in a million pieces.

This makes sure you have the same paint all the way through and there is no pigments in the bottom of any one can.

X-shore. hmmm. "floating/flooding" So this might be a good argument against overthinning single stage?

Rich
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