worf928

Problem:
I need to do some touch-ups of the paint in the engine bay, wheel wells, etc.
Ideally, I'd like to get a rattle-can of the correct paint. The places that need to be touched up will be mostly-hidden and there are plenty of good places to 'kill a line.' The primary purpose of the touch-up is to prevent rust.
I've had good results from places like http://www.automotivetouchup.com for exterior touch-ups.

Alternatively, I could do with something mixed by a body-shop for an airbrush / spray gun.
But, I'd like to get some background education if I can before I start.

The 928 in question has factory metallic paint. It's a '90 which, on the exterior - AFAIK - is a water-based metallic with a clear coat.
I was once, long ago, told by a 'body man' that the non-exterior paint is the base color without any metal flakes.

And no, this 928 can not 'go' to a body shop. It's not a roller.

Questions:
1 - does anyone know, exactly, the paint system used for the non-exterior paint on a factory metallic 928? Water-based acrylic? Clear-coated?
2 - is there any way to determine a 'paint code' for this?
3 - would this be an obvious thing for a good body shop to mix-up?

TIA folks.

Catorce

What *I* would do is get some of the stuff in the attached picture. I am not sure where this stuff was mixed, but a can of it came with my '07 Turbo. Let me tell you, this stuff is awesome. It is single stage paint, meaning it does not need to be mixed with any catalyst. It's a bang on rendition of the color, and while I would not use it to paint exterior panels, it would be excellent on the stuff you are using it for.....mask and spray.

VERY durable, I use it for touch ups on the 07 all the time. The reason for this is the car has a complete Techart body kit and it is very low, the nose (which is paint) is always scraping. This stuff holds up just like two part paint.

If your car is metallic, I would just use this stuff to hit the engine bay with it. Sure, it's not 100% accurate to have metallic paint in there, but do you care?

Herman K

Follow the link to learn more about the POR 15 line of products I have used them for years

https://www.por15.com/Complete-Kits_c_16.html

Use this to stop rust and paint over it to match color

docmirror

I know you want expert analysis and I'm not one, but I have painted a couple cars, including Porsches. The paint changed over the years of production, and even different chemistry for the metal work and the plastic bumpers which were hard to paint due to the materials, and the flex.

In 1991 the paints changed due to some enviro regs, and there were some water based, but pretty sure the 1990 was all Glasurit base/top coat in lacquer.

Your car is black, but is metallic? If so, that would be a paint to sample custom color. The black in 1990 was code 700(non-metallic gloss), You can't match what was sold back then anywhere. Even the chemistry of the Glasurit products has changed due to VOC limitations. Further, what was on the car in 1990 has faded, and oxidized enough so that going back with the original formula is a waste of effort. Take the gas door(or hood) off the car, clean the inside of it very well. Take it to a paint shop, decide on a chemistry that you, or your painter are comfy with and have them do a paint to match. This will be your best bet for getting the color, chroma, and density you want to match. If you are doing under-hood, it will need to be cleaned with the prep stuff that the paint store sells, and not just your regular paint thinner, or reducer. Chance of fish-eye due to contamination of gas/oils is very high. Clean, clean, clean before painting.

Edit; here are the paint codes, I don't know which color you have. The location of your paint code is here too: https://www.928gt.com/t-928paint.aspx
Note the water based starting in 1991.

worf928

Thanks for the thoughts so far. Responses in no particular order...

I'm reasonably familiar with POR's offerings and have used them. Notwithstanding rust, the base coat color needs to be 'on top' and that's the top-of-the-list issue.

Color in question is Velvet Red metallic. Doc Mirror: No idea where you got black or '90 for 'my' 928. If it was black I wouldn't be here. You are correct though, that the water-based paints on 928s started in MY'91 not '90 like I thought. Glasurit is a BASF trademark used on at least three paint systems currently.

What's on the outside in terms of 'paint system' NOW is not relevant as it's a complete repaint. Remember, I'm hoping to figure out what was on the inside from the factory.

Why were these need-to-be-painted non-exterior areas not dealt with by the shop that did the exterior paint? Let's not go there. Short story: Major client scope creep and a long, long story that makes me angry with body shops in general and the subject body shop in particular.

I'm hoping to avoid additional scope creep by simply doing spot touch-ups in a thoughtful manner. The alternative is to strip the engine bay to bare metal and do it all. That actually might end up being the best method. (H311, in hindsight, I'd be 'ahead' now if I'd stripped the entire car to a bare shell inside and out, but that's part of the long story.)

One area might fly with a single stage metallic. Spots in the wheel wells not so much. But, there are ways to blend that so that it's not noticeable.

I would like to know what I'm dealing with though, in terms of what was the 'interior' base coat from the factory. This is especially true if I need to get something mixed: I've too much experience with body shops in this area insisting something is true when there's a preponderance of evidence that it isn't. So, I don't trust them to know what's what on a 928.

worf928

That's a great lead. Not necessarily for this task, but perhaps for others. Thanks.

drooman

Dave.. I feel your pain on the body shops... best bet is to have them do bodywork and paint, and that’s it. As you observed in hindsight the highest probability of a desirable concours quality outcome is to hand them a bare shell. This is a generalization of most body shops, I’m sure there are exceptions.
That said I wouldn’t get too hung up on the original process from Porsche from almost 30 years ago. The appearance generated by the old process can always be recreated with modern products and techniques. On one of my light green metallic cars I needed to do similar work, the exterior and jam repaint was spectacular, but trunk lining, engine compartment, and wheel wells were a mess of former color, overspray, and sloppy black cover up. Fortunately I had an original light green metallic car right here, and observed the original flat light green metallic in these inner areas. I never figured out the original factory process, but theorized they just thinly puffed the inner panels (often leaving various areas of exposed primer) then fully painted the exterior.

After a number of test iterations with light green metallic base coat I was able to recreate the look. I ended up having to intentionally dry-spray the areas to get it right...then satin-cleared it. That step took a few tries as well. Next time I’d try it with single stage if I could find it.

This was a 1978 car, with a different color, but I’ll bet you’d find you can create the exact look you want without trying to use products from 30 ago. Hopefully you have a nice original section of the inner paint surface that can copy. Good luck!

docmirror

Sorry, I got you confused with another guy painting a black 928, and I'm working a black car now.

Best bet is still to remove the gas door(if the inside is not metallic) and have the paint matched to that. The comment that the interior spaces of the exterior are painted with the same paint sans the metallic makes a lot of sense. However, since I was not a builder of the 928 back in the 80s/90s, I do not have empirical evidence of such. When a car is painted at the factory, the interior spaces of the exterior are done first. The cabin, engine bay, trunk/hatch area are the first thing that gets paint. There is sometimes evidence of some exterior overspray in the inside of the fenders, and behind the hatch deck where you may see a bit of metallic bleed over. After the interior spaces are covered, the car is painted from the top down in most booths and the air circ is from top to bottom. This provides the best visual coverage of the paint up at the top, where it is most visible. If you look at the paint closely down under the rockers, and behind the rear wheel well, you can sometimes see a lack of detail, or loss of coverage due to the air circulation drawing the material away from the body. This used to be a problem with lesser value cars, and not so much Porsches. Luckily, those places are also least affected by sun, so they don't suffer as much damage over time as the top of the car.

I will offer again, the best bet for paint match for an almost 30YO car is to use a current sample from the car, and take it to a paint shop with the paint system of your choice. A lot happens in 27-28 years with oil, grease, heat, fuel, coolant, water, dirt, etc. Unless the plan is to remove all the hardware, and paint the entire bay, matching is best done with what you have in there currently.

JWise

I don't think Velvet Red Metallic, 81L, was water-based. This color code was only available in 1989-1990. The factory workshop manuals don't show any water-based paint codes until the 1991 model year.

The shock towers on mine look metallic, as does the area around the lower hood latch. Not sure about the walls of the engine bay, tough to tell if they're metallic or not.

I have some spray leftover from Paintscratch.com. It was used for the rear tow-eye cap. Here's what it looks like:

docmirror

Open the gas filler door, what does the inside paint look like? The car was painted with the gas filler door closed.

JWise

Mine's metallic.

docmirror

If the shock towers, around latch, and inside gas door is metallic, I"m going to say that the inside body spaces are all supposed to be metallic. Likely without the clear over, or they may have mixed a little clear in the base to give it that matte/satin finish.

Since the Velvet red metallic was a very rare color, they had to mix up and spray one car at a time. Not like they were doing 5-20 black cars in a row, or 8 silver cars in a row. Pretty sure the whole thing was done with one base/metallic mix, and one clear coat. The interior spaces may not have any clear in them at all, but do have the metallic added.

worf928

Getting back to this...

After examination with a magnifying class and more googling it would appear that:
- The chassis paint may be base w/Metallic (contradicts what a body shop told me a long time ago.)
- For two-stage metallics it is the clear coat that causes the base to look 'really metallic.'

I have a stack of small aluminum test panels and a rattle can of 81L (VR Metallic) and a can of clear coat. I just ordered both white and gray primer.
So, the plan is to shoot some test panels with the combinations of primer, base, and clear coat and to see how they turn out.

FredR

Dave,

No idea if it helps at all but my GTS is Cobalt Blue metallic. When I acquired the car it had some damage to the paint in the engine bay [brake fluid] and the rear wing needed respraying. Porsche gave me the paint code and I had some mixed at the local Jotun outlet. I understand the paint was a cellulose based paint [the smell sure indicated such] and we did the remedial work in the engine bay without any clear coat and I understand that was the way they left the factory. The engine was out at the time and when the job was complete you could not tell any difference between the freshly painted surface and the original unmolested surfaces. The rear wing of course had a clear coat applied after the base coat. The GTS was first registered October 92 and obviously built some time earlier.

Whether they used different paint types for different regions I have no idea but I doubt it.

Rgds

Fred

docmirror

While it may be possible to get a nitro-cellulose lacquer in Oman, or some other esoteric locations, it will not be found in the US for auto paints(VOC restrictions, EPA, etc). It will be acrylic lacquer in the US. However, if one wants nitro-cellulose lacquer, it can be bought from musical instrument refinishers, usually in pint, or maybe quart sizes at some kind of huge price. Also, the correct reducer/thinner must be used because nitro-cellulose lacquer cannot be thinned with acrylic lacquer and vice versa. I would avoid nitro-cellulose products unless one is an expert at instrument refinishing.