Touch up on HOK Gamma Gold

[Pchrosto]

Hi all,

I am continuing to paint my Fiero piece by piece, and am finishing up the rear clip. The rear of the car is going to be HOK Gamma Gold, and the front will be white. Inevitably, every time I sand the first clear coat, I hit an edge or high point with the 500 grit sandpaper and go down to the primer.

Once I have the piece completely sanded and ready for final coat, I try to touch up the sanded through areas with a Sata Graph air brush. I apply a light spray of a medium gray base coat (the same shade as the original gray sealer), then over coat it with Gamma Gold that came from the same can as the original paint layer. However, no matter how I apply the paint, the touch up area always comes out lighter than the original color on the part.

I have included two pictures that show a spot touch up and an edge touch up. Can anyone tell me what I'm doing wrong??

Thanks!

Pete

 

[TAZ]

When you spray with an airbrush, the metallics do not lay correctly, plus the metallic will settle quickly to the bottom of the airbrush thus spraying metallic before the pigment. So your color will end lighter.
You need to resand those areas and respray with a mid to larger gun.

Example. I can take a normal size spray gun and spray it, and end up with a color the way it was intended.
if I barley pull the trigger with the same paint in the gun and hold it close, I will end up with a lighter color (hope that makes sense)

So, you just need to recreate your original spraying technique as close as possible.
Don't use an airbrush to try to spot in a metallic color

 

[Pchrosto]

That makes perfect sense. Learn as I go, you know.

Since the rear clip is in final clear, can I just lightly sand the areas that need touch ups (or lightly re-sand the entire clip?), blend in the Gamma Gold with a touch up gun and re-clear the entire clip? Also, will the touch up gun be okay, or should I use the original gun which will have a larger pattern?

Thanks for your help!

Pete

 

[Wydir]

I will take a shot in the dark and say the airbrush is not giving you a full wet coat and is going on dry causing the metallic to stand up to much in turn causing a lighter effect. I only sand my clear with 600 only on a run and the rest with 800grit or finer. There is really no reason to use 500grit on clear you will just keep causing yourself issues like this. If I was to repair that area I would scuff with a red scratchpad(where the base would need to go and the rest I would scuff with a gray scratchpad where the clear would go) and use my full size gun and blend it then reclear the panel. but I am also not a HOK user maybe Taz has a few tips he could give ya. hahaha just when I post this Taz has already beaten me don't know why it didn't show up earlier oh well.

 

[Pchrosto]

The reason why I use 500 grit on the first clear is because the HOK manual says that anything finer will not give enough "tooth" for the final clear. But I agree that you can get pretty aggressive with 500 grit, which spells disaster near the edges. From now on, I think I'm going to tape off a 1/4" from the edges and not sand them at all, unless there's a run. Maybe just hit them gently with red Scotch Brite before taking the part into the booth.

I'm trying to push myself on this project and am shooting for a "show car" finish, even though its going to be my daily driver (thus the reason why its taking me so long to finish it). Again, in the HOK manual, it says that if you're going for a show car finish, then you need to sand the first clear so that all of the shine is gone. I'm beginning to think that if I do that with 500 grit, I'm taking off so much clear that I'm risking going through it and the paint at any time (which, of course, has been occurring). And even if you get the shine off of the surface, there are still tiny craters that remain; but I believe that the final clear covers them up sufficiently.

How far down do you sand before applying the final clear? Any general rule of thumb?

Thanks for your input - the replies I get from this forum are really helping me understand where the boundaries are!

 

[Wydir]

If you sand with 500 grit and still have shiny spots left you have a bit of an orange peel problem, And maybe a spraying problem like your putting it on to dry. when I clear, On my first pass I will do a light coat, And then after a 30 second flash I will do full wet coats usually 2 or 3 so when I do go to sand I may take a coat or 2 off during the sanding and buffing stages. but after you clear the finish should be fairly flat with minimal peel if any. using a gray scratch pad to scuff the low spots is exactly what I do as well and should be good enough bite for the clear.

 

[Pchrosto]

That makes sense. I think I'm going to add a bit more reducer to my first clear to get it smoother, then after I block sand I'll use the gray scratch pad near the edges, making sure not to hit the edges. That should help prevent me from sanding too hard and going through the finish.

Thanks for the advice!

 

[Pchrosto]

Okay, I had a chance to hit the rear clip with gray and red scratch pads this weekend, then used the original gun (that I used to spray the gold on the first time) for touch up - and the result was fantastic! I know where all of the air brush touch ups were, but I can't see them now even under bright lights! I cleared over the entire clip one final time, and the clear turned out like glass. Its not going to need much sanding, and the buffing should go smoothly as well. I am going to tackle that this weekend and hopefully finish it so that I can move on to the other parts.

Thanks so much for much for your ideas, Wydir and Taz - I don't think I could have gotten as far as I have without this site!!!

Pete