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jav
07-16-2008, 03:41 PM
I have a very old car that was repainted in the late 70's and is still showroom. There is a small scratch in a very large panel (with no seams) that I'd like to touch up without reshooting the whole panel.

The problem is that I know the paint brand was PPG and it was single stage but I have no idea what fomulation it was... I presume acrylic enamel? Any suggestions fro blending a small area on old paint?

thanks

John

hotrodmarge7
07-16-2008, 07:37 PM
I just posted a help wanted on this subject my self. I was told to get DX840 Blending by PPG They say it works well and you never see where you start and stop. I am picking some up topmorrow and will do a test patch. I'll let you know how it works!

jav
07-16-2008, 09:19 PM
I had read that and I went on PPG's website and did a search but found nothing. Most vedors around me sell (and I'm most experienced with) Dupont and they don't even mix Centari anymore. I had them camera matched the color and they recommended (and mixed) a Nason Acrylic enamel single stage. The mix ratios suggests it's closer to a polyurethane requiring reducer and activater. My supplier didn't have any blending solutions other than for clears.

I will try to find a PPG reseller but I wonder if the PPG blender will work with the Nason formulation? Or, does anyone know if PPG offers a single stage acrylic enamel anymore?

Thanks in advance and HotRod.. please let me know how you make out with your test piece.

Serge
07-17-2008, 09:18 AM
Or I should have said, blending reducers are just slow reducers...You can use a slow reducer if you have one on the shelves...

You should not thin out ss urethanes too much, clear is what should be added as a blending agent...just use a compatible clear in the same line to make the ss more transparent.

Use a slow solvant in a separate gun to spray the surounding blend areas to melt the overspray. Just a sprinkle...if you spray too much you will end up with runs...

When spraying straight reducers it is wise to use less air pressure in the gun as straight reducer is quite thin...

With acrylic ennamel you must be sure it is fully cured otherwise it risks lifting....if its old you should be allright...

Phil V
07-17-2008, 09:33 AM
The simple truth is that you're probably opening up a can of worms, brought about on several different levels. For starters there is no way of knowing if the previous repaint included a hardener additive. If no hardener was used then the paint will lift like you applied paint stripper when you trying to spray your new paint over it. Secondly there is NO way of getting a quality blend job even if a hardener additive using new single stage acrylic enamelover that old paint, it just won't come out right regardless of what you do. You will end up with a "halo" around the paint blend, now way around it. Thirdly the odds of a good color paint match are somewhere between slim and none. If you're looking for an invisible repair - its not going to happen.

I know thats not what you want to hear but its what you need to hear before you jump into your repair job with both feet. I have painted literally thousands of cars with acrylic enamel so I have a hands on background of what I'm talking about.

Phil V
07-17-2008, 09:39 AM
What color is the paint and is it a metallic or not ?

jav
07-17-2008, 12:14 PM
Phil,

you're dashing all my hopes but... I respect your experience and opinion. Here's some more info.

The color is red- no metalic. The Nason acylic that my supplier mixed up yesterday (based on the camera color match system) is a perfect match.... to where he took his readings- which were on the hood. He took his readings there because it was the flatest spot ( I new we should have done the quarter but didn't push the issue).

As I feared, the area that requires repair (on the side of the rear quarter) doesn't match as well. It's close, but not perfect. The sides of the car appear darker and richer causing me to beleive the top paint surfaces have faded ever so slightly more than the sides. I'm planning on having them smaple the sides to see if they get a different shade as I'm pretty impressed with how well it worked matching the hood.

The bigger problem is the Halo'ing that you eluded to. Many years ago, I had miserbale luck blending enamel spot repairs but as I recall, all were metallics. I was hopeing that on a solid color, a good color sand and polish would produce a consistent surface sheen if i can get the old and new paint to melt together. I do want an invisible repair as this is what the car deserves.

Thoughts?

Serge
07-17-2008, 02:46 PM
Red is the worse fader and it will be difficult to match that's for sure...

How bad is it now...what kind of car is it? Any body line you could use to fool the eye in your repair...?

jav
07-17-2008, 06:25 PM
old Ferrari- no hard lines... looks a lot like an old Shelby Cobra (the 2 seat english version, not the Mustang).

Phil V
07-17-2008, 08:46 PM
JAV, Old Ferrari that has a resemblence to the old AC Cobra - That conjures up visions of the old Ferrari 250 GTO (big BIG bucks).

The fact that the new paint is a little lighter shade of red than the existing paint on the quarter is actually a good thing ( I know, that sounds counter intuitive). But - red is the only color that darkens down as it cures. If that is a real Ferrari then someone should have their nads cut off for getting anywhere near that car with acrylic enamel.

The following is common practice among high end cars (like a Ferrari) that have a relatively small scratch or paint chips. Dig out your trusty camel hair paint brush (small tip) and hand fill in that scratch with the brush and your new paint you had mixed. Let that sit for a couple days (preferably in the sun) then LIGHTLY wetsand with a small block and 1500 grit the excess new paint outside of the scratch groove. Then apply another coat of the same paint just as you did the first time. Keep repeating that procedure until the whole scratch is filled in. Get some hardener for your new acrylic enamel and mix up a very small batch of paint with the hardener each time you brush touch the scratch. Over a relatively short amount of time that will give you as close to an invisible repair as your likely going to get. In most cases you can get away with a repair like that with a solid color. It don't work worth a darn with metallic based paints.

Could you post a picture of the existing paint damaged area ?

Len
07-17-2008, 11:19 PM
My guess is that, if the last paint job was done in the 70s, it could very well be lacquer. If it's lacquer you may be able to get some and spot repair the area. Try putting some medium or slow lacquer thinner on a clean cloth and rubbing it on the surface near an area that will be repainted. If the paint melts and comes off on the cloth it's probably lacquer. Getting the lacquer could be difficult.

If it's lacquer you'll either need to use lacquer or something compatible. If it's lacquer and you don't want to touch it up with a brush you may end up stripping and painting the car but that's a lot of work to fix a scratch.

jav
07-18-2008, 07:43 AM
Phil-

Good guess, it is a 250... but not the GTO. Still a very special (big buck) car.

It's funny you mention the camel hair brush... that was my first thought to keep the repair area as small as possible and I was just too worried about repeated sanding to cut it down and figured I'd use an air brush instead.

Len,

I don't think it's lacquer... It would be fantastic if it were as I've never had an issue blending lacquer. Although I don;t know if i could get red lacquer. I actually still shoot lacquer (black/clear mostly) and this doesn't have quite the same look. I'll to a test swap in an unconspicuous area to be sure but the paint looks alot like a buffed Centari or possibly Imron (in whatever PPG called their versions).