Paint defects - water spots or something else?

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heinzbush

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Hi All,

I am trying to get the paint of my 993 perfect and worked so far with Ultimate Compound and Ultimate Polish. While in general, I get ok results, when I use a flash light, the clear coat still looks like it has many defects which are not swirls, scratches, etc... but rather like tiny "craters" or "small embedded areas": am I right these are watermarks? I probably should hit with something more aggressive like M105?


View attachment 65062View attachment 65063View attachment 65064

here is a good picture in full resolution: Dropbox - IMG_1286.jpg


An additional, major defect is on the engine bonnet... looks like it goes through the clear and paint all the way to the metal... any tips on how to "attack" this? I guess respray is the only way...

View attachment 65065
here is another good picture which for some reason doesnt upload: Dropbox - IMG_1248_.jpg
 
Unfortunately your pictures are very small (even the "full resolution" ones), so, it's hard to say, but I tend to see the defects in the last picture having a very sharp, yet thin line, and a zigzag-like pattern. Which I wouldn't say are typical for water spots, because in my experience those are more round and their edges less sharp usually. However, I remember having seen similar patterns of defects on cars that had tree sap or pine tar sitting on them, and that ultimately ate through the clear coat, down to the very metal. Once the sap and resin was removed, the defects in the clear coat had the very same zigzaggy pattern.

And the other pictures with the many spot-like defects look like tiny rock chips to me, like what you'd get if somehow gravel would hit the paint in large quantities, yet at relatively low speeds. That said I also think I see tiny hairline like defects in those pictures, which I guess would be typical for either a very heavy direct physical impact at that spot, or signs of imminent clear coat failure, when it would start to peel off soon. These defects could be also the sign or result of a very poor aftermarket (re)paint job.

Did you measure the paint thickness at the pictured areas? What were they, compared to like door sills and unaffected areas?
 
Has it been repainted? Sort of looks like orange peel.


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Thanks a lot for all your answers...

with regards to the finer defects (the first part of my initial post): I only have a magnetic paint thickness scale (one of these pens) which indicated green (no respray anywhere of the car and normal paint thickness) when I bought the car. I dont have it with me right now as I borrowed it a friend of mine.

I tried to get better pictures and I uploaded them on link below. The pics are actually quite big, you have to zoom in to 100% to see it really large.
The defect is difficult to describe and not everywhere as bad as on the pictures. Keep in mind, the car is 23 years old and probably never had paint correction done... from a foot away, the paint looks perfect and mirrors nicely, however if you get really close you can see that the surface is simply not even, but has these small craters / "ups and downs"...

The pics are from the rear fenders of the 911 where it is worst... I guess since this area is prone to stone hitting, water drops staying on, etc.

Pictures


The second (deeper) defect could very well be from tree sap. Crazy that this goes all the way through the clear, paint, all the way to the metal. It is on the back of the car. You think its worth trying to try to fill these many tiny holes with a color/clear coat mixture and then wetsand?

THANKS!!
 
Well, you could buy a relatively cheap, yet good paint thickness gauge with an LCD display for about $150-250, that actually tells you in microns (with an accuracy of a few microns) of how much paint you've left on a metal substrate. They won't work on plastic bumpers (you'd need more expensive one for that, that cost >$1000), but will work on essentially all metal, even non-magnetic ones.

The thing is: even if you're not a professional detailer a proper paint thickness gauge is essentially a must when doing anything more than just light polishing on a car, because every time you do any kind of serious compounding, correction or wet sanding, you run the risk of burning through the clear (or if it's single stage, then through the base paint) to the point where the panel has to be repainted. So, it could very well pay for itself even for the first time.

The problem with these pen type gauges are that they're not very accurate, and they're only telling you very roughly about the thickness of the paint, which hinders you in making a proper assessment of how long you can go on with sanding or compounding before you're risking ruining everything.

As for the pictures:
1. Regarding IMG_1300 and IMG_1302: they still look like tiny impact damages to me. You could try correcting them with either compounding, or if that seems insufficient, then with wet sanding, but I wouldn't recommend trying anything without a proper thickness gauge. Or if they're only obvious when inspected closely and in focused light, but not reallt noticeable from regular pass-by distance and in everyday ambient light, then you could just leave them as they are, as they will be noticed by no-one.
2. IMG_1304 and IMG_1309: I'm not sure what to make of these, or where to look at. Actually 1309 looks like regular orange peel to me, but this could be also because of just the picture.

As for the tree sap damage: the problem is twofold. For one, the actual crack in the paint going down to the bare metal is usually not wide enough to be properly filled with paint. You can try it, but you will either create a huge (well, relative to the width of the crack) paint bump over the spot, or anything that you put in the crack will be removed at the first attempt to compound it. And the second thing is: the crack itself is just a small portion of the defect, as tree sap usually falls and sits in a drop shaped form on the surface, because of which the damaged area is usually larger than the crack; it's just the where crack is where it has eaten completely through the paint. But the damaged areas as a whole is larger, so, you might have compromised - or even already missing - paint in a larger spot. And this is where a proper thickness gauge comes in the picture again - because I heavily advise you to do anything aggressive to that area without assessing its current state, and the amount of paint still remaining there.

The problem is that once you try to touch up that area with a "larger" amount of paint (that will actually remain there), you'll have to wet sand it flat (otherwise it will look even worse with the touch up paint that it does now), and unless you've enough wiggle room left for that, you're risking burning through and compromising even larger areas of the paint - which obviously does not make any sense, if you want improvement, not degradation of the current state of the paint.
 
Thanks a lot for the answer...

with regards to IMG_1304 and IMG_1309: this is how it looks when you move further away... so the damages on the first two pictures are taken very close..

I understood that there is nothing to be done at this stage without a paint thickness gauge, so this is what I'll get now and come back to this thread after measurements!
 
What machine did you use to work on this paint and how long did you work it? I mean, like, did you keep going over and over the very same section, very slowly, or for more than a few passes, and for longer than one or two minute(s)?
 
itsgn said:
What machine did you use to work on this paint and how long did you work it? I mean, like, did you keep going over and over the very same section, very slowly, or for more than a few passes, and for longer than one or two minute(s)?
Click to expand...

Hi,

I have a DA polisher, went over it with 3 passes, not for a long time, "average speed" and nothing aggressive (soft foam pad, Ultimate polish)... KEEP IN MIND: these defects are not introduced by the polishing. They were there before... I'm just looking for a way to get rid of them... but wont go aggressive (e.g. M105) without getting a paint thickness gauge first...
 
Okay, I just asked, because if you work the pads on the paint too long, with no pause in between, similar defects can arise from overheating the paint. But then this was obviously not the case here.
 
heinzbush said:
... oh since you mentioned you were not sure what to look at I indicated it on the pics... It is very hard to capture with a camera due to focus / reflection... basically wherever it hits the light, the surface is not smooth and there are tiny craters, defects...

View attachment 65068

View attachment 65069


Big resolution on dropbox:

Dropbox - paint2 - Simplify your life
Click to expand...


Hi all,

finally got my paint thickness gauge and measured all over the car.

In general, I get about 120 mils on average. Also on the area with the defects highlighted above (most of the defects are on the rear fenders)
There are only two areas that differ:
- doors: here the reading is a bit less, about 100 mils with a minimum of about 90
- front right fender around the headlight (here I get up to 200mils, maybe there was a respray, even though I cant see it with my eyes)

I guess this is green light for going a bit "more aggressive" using a compound like Ultimate Compound or M105, even though I still dont know exactly "what these defects are / where they come from"...
 
The 120 microns (not mils!) is the typical factory paint thickness, which either hasn't been yet touched by any polishing process, or only slight polishing or compounding was done to it. The thickness of 90 microns indicates that some heavy correction was already done to that area, which left you barely any clear coat to work with. I definitely wouldn't try to wet sand any areas that have only 90 microns, and would be also careful with compounding there, because there's only possibly another 10 microns left which you can remove without definitely compromising the paint. 200 microns (especially if the rest of the car is <120-130) is a definite sign of an aftermarket respray of that area or panel.

However, take note, that the thickness of >200 doesn't necessarily mean that you have heaps of clear coat to work with that you can remove safely, because you just don't know how much of that >200 microns is the thickness of the clear coat, of the base paint and of the filler bondo that might have been applied to that area under the paint. And because the thickness gauge can't differentiate between these, and what it measures is the total thickness of materials between the metal panel and the surface of the paint.

Anyway, what I'd do would try doing a smaller test spot on the affected area (provided it has a remaining paint thickness of about ~110-120 microns , minimum), do some relatively heavy compounding on it, and see whether it changes anything. I'd always make sure to only do a few passes at a time, and check whether I'm not making things worse. I'd also check with the thickness gauge how much paint I've removed (even though that should be only a few microns with each pass, maximum). Obviously if things start to get worse, I'd stop the process, and either leave it as it is, or if it's not obviously much worse, then I could try blending it with the rest of the panel by gradually applying the same process (but with less and less passes and pressure) over a smaller section towards the rest of the panel.

However, if things didn't get worse but I'd see no improvement either, then I'd continue the process until I've removed 10-15 microns in the test spot. If I'd still see no improvement by that time, then I'd possibly try wet sanding with a hard backing pad at a different (!) spot. This will require even more caution and more frequent checking of the amount of paint abraded, because it will go a lot quicker than with the compound. And of course I'd to use the compound to take out the scratch marks. But I'd pay attention not to remove more than possibly 20 or 25 microns max, so, that I'd be still over >90 microns.

If this wouldn't produce satisfactory results either, then I'd have to chose between the safer option of leaving things as they're and live with them, or continue the compounding and/or wet sanding process and remove even more of the clear coat in hopes of getting an improvement. However, if I had none until there, chances would be slim at that point that abrading even more of the clear coat would bring me noticeable improvements. And of course the more I'd remove, the higher would be the risk of me burning through the clear coat, or even possibly exposing even more of the defects.

Well, that's how I'd approach this thing, if I'd be sure that I want to do something with those defects. How you want to and will approach it.... well, that's up to you.
 
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