Streaks when using metallics

[Pchrosto]

Hi all!

I am fairly new to painting, and I'm running into problems when I try to paint with metallics. I use House of Kolor paints and follow the HOK technical specs to the letter. I am attempting to paint a trunk lid using HOK "Gamma Gold", which is a darker gold metallic, with the color being on the orange side.

When I painted it in my booth, I had it hanging vertically, and it looked very even. After I sprayed the first coat of clear, it looked even better. But when I pulled it out of the booth today and laid it on a table in preparation of color sanding the clear, I can see darker and lighter streaks and blotches when I look at it from an angle. Again, if I look directly down on it, it looks pretty even!

So, what am I doing wrong? I set the fan on my DeVilbis gun between 6" and 8", lay on the paint with 50% overlap at about 6" from the surface, 10 psi at the tip (HVLP), just like the tech manual says. Wrong approach?

Another thing that I may have done wrong was to lay down a white sealer before the gold base coat; I wanted the gold to have a brighter cast to it. Would that contribute to the problem as well? If so, what color base should I lay down?

It is so discouraging when the object looks great in the booth, and looks so rough when you bring it out....

 

[TAZ]

It could be because of your gun settings and possibly the way you applied the paint.

I definitely wouldn't have used white as a base or sealer under Gamma Gold. I would suggest using a medium gray. This should help coverage and help keep the 'mottle' to a minimum.

 

[Pchrosto]

So, should I mix equal amounts of black and white sealers to get the gray, or mix a little more black than white to get a little darker gray?

I'm also wondering if I should open up the fan on the gun from 6" to 8" so that the paint won't get too concentrated on the passes. Your thoughts?

Another thing that a friend mentioned to me today was to make the passes in the same direction each time so that the flake will lay down in the same way on each pass, which makes sense to me. I was spraying from the top to the bottom with the first pass, then spraying from bottom to top on the second overlapping pass, and so on. Maybe that's contributing to the "banding" I'm seeing?

 

[Pchrosto]

Would using the KS12 Silver Metallic Primer Sealer work to support the metallic Gamma Gold? Or would it be too bright as well?

 

[TAZ]

Normally, I mix some black with the white sealer and just tint until I feel it's a good sealer under my basecoat. In your case, some sort of medium sealer should work great for you.
You can use that silver metallic sealer. For some reason I tried that a few years ago and really didn't like it. Can't remember the reason though. And yes, I don't think the silver sealer would be a good sealer under Gamma Gold

You can always mix your gray and white sealer, and then just add a TAD bit of Gamma Gold basecoat. into the sealer. I was told up to 10% is fine for the sealer with no ill effects.

About what your friend is true. Just go one direction on all passes. In the older days with the wet enamels, yes, you wanted to work it out until you you got the mottle out by doing crisscross patterns, but not with todays basecoats.
I hold the gun about 6" or so and put on medium coats with the correct weather reducer.

 

[Pchrosto]

Thanks Taz, I took your recommendations as well as thinking of a few ways to give the lid a better finish, so I tried again over the weekend.

I sanded the lid down, then mixed a sealer coat of 25% black to 75% white; that gave me a good medium gray, just like you said. I sprayed it down evenly, let it dry, lightly sanded it with 220 grit, then sprayed the gold again; except this time, I did a few things differently.

I used the Sata 3000 gun that I usually reserve just for clear coats instead of the Devilbiss, and changed the pattern of the coats. I did not mean to say before that I tried a criss cross pattern; I spray in one direction, say left to right. However, instead of laying down the first pass from left to right, then laying down the second pass from right to left, I layed down every pass from left to right, overlapping each pass by 50%. That really made a difference, I believe. The gold looked perfectly even (while still laying horizontal in the booth, that is), and I used the Sata gun again to lay down the first series of clear coats.

It looks really good so far, but I always get more dirt nibs in the paint when the object is laying horizontal rather than vertical. So, I'm going to sand it out in a few days, prepare it for the final coats of clear, clear it vertically in the booth, then see what sanding and buffing will do to it. You interested in seeing a picture when I'm done?

Thanks again for your prompt replies and great suggestions. I'm having fun again!!

Pete

 

[TAZ]

Pete,
Glad to hear you are starting to get it to work out for you!

I would guess that combination of the 'gray' sealer and the way you applied the base along with the gun you used made the difference.
Be sure you are also using the correct temp reducer. This helps even more (if you aren't already)

As far as sanding the "sealer", you don't need to do this. This is to be applied as a wet on wet. Which means you spray the sealer. Let it dry for a short time (normally about 10 minutes). Then apply the base directly over this.
Let's say you get a big piece of dirt in the sealer....just use a piece of 1000 wet to sand it out. 220 is pretty coarse to be sanding a sealer.

You can do the same with the base, but if you are painting a lighter metallic, you'll need to recoat the area you nibbed.

Sure...by all means, post some pics if you would like once you're done.

 

[Pchrosto]

Thanks again for more info, Taz - I'm absorbing it as fast as I can!

I mis-read the technical sheets for the sealer; there are sanding instructions, but if you read carefully they apply only if you let the sealer dry for more than 3 hours before applying the base coat. I also saw a touch-up video where they showed the painters wet sanding the sealer coat, but they must have let it dry over night. I'll make sure to leave it alone from now on and apply the base coat directly. Saves some more time, too!!:sillyme:

As for the reducer, I use fast reducer because my booth is around 68 degrees and 35% humidity. Should I be using a medium reducer instead?

Thanks for all of the tips!

Pete