"Mottling" Silver Problem

[DennyG]

Just finished spraying a car Silver Mist-{silver} with LIMCO base using a Devilbiss "compliant"HVLP gun and have some slight "mottling" in a few areas.
Not bad,but room for improvement.:rolleyes:
What is the trick for getting it to be more even? It was a 66` Dodge and the 1/4`s are about 6ft. long. It has a little on the sail panel and some on the roof. I tryed "fogging" the last coat,but that seemed to make it worse.:(
When I was cutting in my little HVLP touch-up gun sprayed it MUCH more even than the BIG gun wich has a 1.3 tip. I`ve sprayed pearls and had it go on much better than this one.
I paint about one car a year so,,,,,,, I`m sure its my technique more than the guns.:o

[SHOWCAR FINISH]

These are the causes of mottling...

Wrong solvent
not uniformly mixed
spraying to wet
gun to close
uneven spray pattern
low shop temp

It could be your gun. Turn the cap 90 degrees and hold down the trigger till it runs. Runs should be even. If you have run that's uneven, flip the cap 180 degrees. If the run switches sides it's the airhorn. If it stays the same then it's an obstruction in the needle and the gun should be thoroughly cleaned.

[Phil V]

was the mottling visible before or after the clear was applied ?

[DennyG]

Not really,it has such a texture it is REALLY hard tell.
After laying awake most of the night I think I probably put it on too fast.
The fiberglass front fenders have NO mottling,but the steel 1/4`s do. The
`glass parts would have been warmer than the steel and dried faster.:rolleyes:
It was`nt cold but,there would still have been a temp. difference. I`ve seen this before with runs and even colors not matching even when the side of the car was painted all at once.
What do you think?:confused:

[SHOWCAR FINISH]

Are you holding the gun straight on with the work at all times? I gather mottling is either from techniques or whatever allows the flakes to gather in wet material. So that makes me think a fast pass won't do that, but a fast pass with the gun heeling may do it.

[Serge]

I try to cut on the material knob so it does not shoot too wet, then I overlap 75% instead of the 50%. This helps alot. You would be better off with a good hvlp gun. I like my Iwatas with the purple cap, also like the NR3000 now that I have had a chance to tinker with it...

Both are better at placing metalics. The other thing that is important is to not shoot it too dry (dusting) this can cause a rough surface that will appear like molting when looked at from different angles. You should always tack between basecoat coats. I like the 3M tack pads for basecoats as I can be farely aggressive without loosing lint. Any loose metalic dust that settles on top and migrates in the clear can also cause some undesirable paint effects...

[stealth1]

Denny,

I believe the problem you are having with mottling is not so much your technique but the materials you are using, mainly the Limco base coat, while it is a thick base coat with good coverage it's metallic holdout is very lacking and I will only use it on work trucks and even then only a solid color and never a metallic because of the same type of problems you are having.

The Limco LC4000 clear is a very good clear for low end jobs and sprays very easily and lays down like glass, but it is very thin and requires at least 3-4 coats for proper film build versus a high solids clear like PPG 2021 that only requires 2. Also if you plan to wetsand and buff the LC4000 clear, make sure to do it within 24 hours after spraying cause it sets up very fast and cures to a rock hard finish making it hard to buff !

Best of luck......................:)

[DennyG]

Thanks for the reply`s
I think you are ALL right. I`m sure its a combination of me,the material and the "compliant" gun.
I was going to use an my old SHARPE siphon gun ,but did`nt:rolleyes:
Wanted to use DuPont ,but did`nt:rolleyes:
Should`nt expect perfection,but I do!:o
Next time I spray I`ll heed your advise.................;)

[SHOWCAR FINISH]

expecting perfection in painting is essential. That way, every little mistake is noted and you'll think back at what caused that. I think that's crucial.

[Len]

I'll tell you that I love BASF products but I won't use their Limco line and mottling is one of the main reasons. When I want a lower cost bc/cc I go with U-Tech or some other less expensive brand but not Limco. You can have your base applied perfectly but when you lay on your clear it can cause the metallic in the base to sink causing dark mottled areas.

One of the ways to stop this mottling is to allow a longer dry time between coats AND between your base and your clear. This problem has very little to do with your spray gun but if you're not atomizing well it may add to the amount of mottling you end up with.

Next time try to use a product that has a polyester base and you'll experience very little (if any) mottling no matter how it's applied or what gun is used to apply it. The downside is that the polyester base coat products usually cost quite a bit more. Limco is almost like applying an acrylic enamel then applying a urethane clear, the base is so thick and wet that it allows the metallic to sink causing the color change.

[962porsche]

when it comes to spraying limco 4 base you have to treat it like any other metallic single stage color even though its a base clear system . you will have to do a drop coat for your last color coat . up untill the last color coat it does not matter if its strippy / blotchy . what i found works the best with limco is on the last color coat let it flash for about 3 to 5 minutes at most then pull the gun back off the panel to about 10 to 12 inches and do your drop coat . a drop coat is just a light dust coat that will drop a very light mist on top of the last color coat you just sprayed down . this drop coat will even out all the metallics and melt into the last coat that is almost flashed off .