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Old 01-17-2012, 12:40 PM
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Check out this picture - Irregularities in Metallic Finish - Is this the NORM?

I've noticed little bumps/clumps/irregularities when I spray metallics (DuPont and others). I usually just let the coat dry and come back and just lightly run over it with my hand.

That takes the clumps/specs off very easily. BUT it also leaves a mark/stripe that reflects differently where I ran my hand over the finish. So this isn't good either.

What am I doing wrong and is this normal to get these specs?
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Old 01-17-2012, 03:16 PM
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Looks like something was in your gun and you shot it out of your gun or something was in the paint and you shot it out of your gun!And when you rubbed it with your hand you changed the lay of the Polly (its reflecting light in a different direction)It happens! You could also have particles traveling down your air hose. Do you run an air filter on or close to the gun and do you change the paint screen in the gun regularly?

Jester
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Old 01-17-2012, 03:38 PM
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Is it dirt or the metalic? the cause of dirt can be a number of things, but metalic not layin down is an easy fix. If you would like my advise just ask,Badawg.
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Old 01-17-2012, 09:03 PM
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Quote:
Originally Posted by badawg
Is it dirt or the metalic? the cause of dirt can be a number of things, but metalic not layin down is an easy fix. If you would like my advise just ask,Badawg.
Advice please

Only a fool doesn't love advice.
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Old 01-18-2012, 10:09 AM
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hope this helps

If your gun seems to work good & you have checked filters. What size compressor do you have? (not enough air volume) to keep steady air pressure @ gun. Base/clear,acrylic,urathane? Old school metalics and the new version of pearl require different needles & fluid tips. Let me know your set up & we can narrow this down.
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Old 01-18-2012, 10:47 AM
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Quote:
Originally Posted by badawg
If your gun seems to work good & you have checked filters. What size compressor do you have? (not enough air volume) to keep steady air pressure @ gun. Base/clear,acrylic,urathane? Old school metalics and the new version of pearl require different needles & fluid tips. Let me know your set up & we can narrow this down.
I've got filtered air (filtered twice before the gun), I don't have my fresh air filtered and I don't always wear a paint suit when painting.

I didn't run that metallic through a strainer (DuPont Chromabase). I just poured out of the can and into the gun.

The gun has a 1.4mm nozzle.

Part of me thinks that it's either contamination from the fresh air/environment in my booth or that it's because I didn't pour the material through a mesh strainer. Not sure but I'm guessing that's the issue. Seems like the metallic is laying out ok. Just the contamination that's a problem.

The other thing I notice is that if I spray more to cover up an area that I touched and deflected the metallic etc, spraying too many layers can make it look fuzzy and not smooth.

How do they avoid contamination in the big auto factories? Seems like it's always clean for the length of the vehicle. Pretty amazing.
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Old 01-18-2012, 11:58 AM
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I think you just answered your question, you didn't run it through a strainer funnel. Might also consider a little reducer to help it lay down, then pour the mix through a strainer to ensure it's got no particles that will lump up.
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Old 01-19-2012, 12:14 PM
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Quote:
Originally Posted by 1971BB427
I think you just answered your question, you didn't run it through a strainer funnel. Might also consider a little reducer to help it lay down, then pour the mix through a strainer to ensure it's got no particles that will lump up.
I agree, and I have a couple of tips: one is if you want flawless: When spraying paint you build a magnetic charge (like when you rubbed a balloon on a wall when you were a kid) it will pull dry over spray back to your car instead of it all going out the vent fan it will also pull other contaminants off your cloths mask gun etc. I have a copper ground post through the floor in the center of my booth 8ft.into the ground just high enough to hook a wire to, the other end of this wire I hook to the car It drains off the static charge. Every time you rub on the car like when you tack it down or wipe it with prep you build up more of a charge. Just hook a wire to any thing thats a good ground (dont trip over the wire) will be good enough to do this.

take your gun apart and clean it good after every paint session ( especially if you only have one gun) just running cleaner through it is no answer!
Always change the paint screen in the gun Have plenty on hand especialy if your using hardner!
Have an extra gun on hand ready to go at your mix station (with 5min tach time or even 15min) you wont have time to fix your gun for your next pass if something were to happen.
Have plenty of mixing cups and sticks If you use hardener dont use the same stick to stir your paint in the can and the paint in your mixing cup, use two different sticks.
Once you pour your paint into the gun never stir it with a stick or anything. your ready to shoot.
Change your mixing cups during the shoot (I mix 1 good wet pass and throw away the cup and grab another if Im using hardener) you may not think it but the paint left on the mix cup is starting to jell & tach like the paint on the car and can slip through your paint funnel filter and spray out of your gun and after the paint is dry you see this little spot you just cant figure out.
When using hardener never mix a bunch of material at once after the first wet coat pass youll know how much paint you need to mix with a little left in your cup. ( like a 1/4 left) To hit any dry or light spots before leaving the booth for my next mix. If you only have five minutes to mix get a helper ( but 5 min. is actually a long time)
I always screen (filter) my raw paint into my mix cup before I reduce or add hardener and then mix and screen again as I pour it into the paint gun This is not a tip I just learned this way LOL
These guys can give you more I type to slow! And factory paint jobs now wouldnt pass years ago! they are far from flawless!
Every one does things different and has different techniques if your ok with yours stick with em

You may know all this already

Jester

Last edited by painted jester; 01-19-2012 at 12:21 PM. Reason: missed 1
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Old 01-20-2012, 07:13 AM
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Great tips and thanks. I was a little worried about straining the metallic out of the mix. But thinking about it again, the metallic is around 70 micron and the strainer is like 120 mesh if I recall. So the metallic should pass through.

Great tip on grounding as well. That's something I've wondered but thought it was just my imagination.

I have been using plastic sheets on the walls near my workpiece to create a little bit of a static cling for dust and lint etc. I think it might help. I also spray the floor down. That seems to help. When spraying a dark color, I'm not as careful about all of this as it doesn't tend to show as much.
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Old 01-20-2012, 04:29 PM
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Quote:
Originally Posted by 777funk
Great tips and thanks. I was a little worried about straining the metallic out of the mix. But thinking about it again, the metallic is around 70 micron and the strainer is like 120 mesh if I recall. So the metallic should pass through.

Great tip on grounding as well. That's something I've wondered but thought it was just my imagination.

I have been using plastic sheets on the walls near my workpiece to create a little bit of a static cling for dust and lint etc. I think it might help. I also spray the floor down. That seems to help. When spraying a dark color, I'm not as careful about all of this as it doesn't tend to show as much.
Dont use plastic. it will only take one time for something to build up on the plastic come off and ruin a good spray job . another tip use your tac rag to wipe your hose and spray gun before you re-enter your booth check your tip every time before you re-enter your booth and clean any build up with a good rag , damp with reducer or thinner.

The best tip you'll ever receive is! what might go wrong will go wrong!!!! Like oh my hose is caught on the tire! but I only need a few more inches ! think Ill just pull on it oh that didnt work Ill just pull harder oh that didnt work Ill give it a little flick! and the hose flips crap all over your project because you were too lazy to walk 15 ft.

Jester
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Old 01-20-2012, 05:58 PM
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In my shop, I've always been fanatic about keeping everything clean. Possible sources of contamination in paint include some things you might not think of. The inner lining of some air hoses can break down. We never drive over our hoses for this reason. And the hoses between the last filter and the gun are replaced regularly.

The gun itself needs to be disassembled and cleaned after every spray session, especially if catalyzed material was sprayed. Paint should be strained. Many mixes include toners that aren't used very often. A pretty big glob can fall into the mix. It may melt in, it may break down into perfect trash sized specks. Of course, the objects being sprayed can be the source. Masking can be used to do two things; keep paint off the rest of the car - keep the rest of the car out of the paint.

If you do get trash in the color coat of a metallic, you can just scuff it out, but the grit of the sandpaper will scratch the metallic particles, leaving a nice pattern that you don't want. So, if you do scuff, you need to apply enough color to hide those scratches. Or, if the contamination is small, you can apply a protective clear coat. Scuffing the clear only scratches the specks, which isn't usually noticeable.

Some painters charge extra for inlaid insects. You might try calling your specks a "Traction Coating"
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Old 01-20-2012, 06:03 PM
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I have an inline dessicant filter right on my guns, just in case anything gets loose in the hose, or after the air dryer. It still gets particles in it that would have been in the paint or gun, so I'm glad I use them.
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