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07-19-2010, 08:55 PM | #1 |
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'scuff' in trunk lid. How do I tell if it's correctable?
I noticed on my car that there's one spot on the trunk lid which looks like a 1" square scuff mark. It looks like lots of very fine scratches in a criss-cross pattern. It's only visible from certain angles in a reflection, and if I run my hand across it I can feel a slight difference on that spot.
The car's white, and there are a few imperfections in the paint, mostly black specks. I am not sure how to tell if this scuff is correctable or not though. I claybarred the car to remove a lot of road tar, and some spots were pretty stubborn. I would be surprised if I"d done this scuff with the clay though, as the rest of the car is fine. My biggest fear is that I try and use some kind of mild abrasive on it, and it's already through or almost through the clear and I make it worse. I'm wondering if there was something like bird droppings on it while it sat somewhere during the delivery process. I'll try and get a picture if I can get the angle right, but if anyone has any suggestion on how to tell if I should try and correct it or just leave it alone, I'd really appreciate it. |
07-20-2010, 03:57 AM | #2 |
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A surface scratch that will `catch' your fingernail is approximately 0.04 Mil (1.0 µ) deep will usually require wet sanding and refinishing
Most other scratches, whithin reason, can be removed |
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07-20-2010, 06:04 AM | #3 |
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@TOGWT: I follow some detailing fora and I noticed that often times more than one micron is removed from the clear coat to achieve correction.
I've never really polished out deep scratches that were white / catched your finger nail beyond the point of full correction. Most of these scratches were "invisible" unless you knew their exact location. However I've seen Clark from Polished Bliss remove several microns of paint to achieve correction, which would also correct a scratch of 2 micron deep for instance? |
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07-20-2010, 06:52 AM | #4 | |
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07-20-2010, 07:31 AM | #5 |
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Thanks guys, it doesn't catch your fingernail at all. It's more that if I run my fingertip over the area, I can tell where it is as it just feels different. Maybe marginally less smooth (the trunk lid has paint sealant on it, including this area).
This is the best picture I managed so far, I'll try and find my old camera which is better at close ups. http://img193.imageshack.us/img193/8752/paintch.jpg The area in question is between the reflection of the garage door opener and the window, closest to the window. From this angle it looks like a smudge or fingerprint on the paint, but from other angles it's completely invisible. When you get closer it appears to be made up of many smaller scratches. I'll try and get another picture showing the detail of that. I already tried a very light application of meguiar's paint cleaner, and meguiar's scratch-x, neither of which did anything. But, I didn't really polish it hard in case I made it worse. |
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07-20-2010, 07:37 PM | #6 |
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Hard to say, but looks correctable from the pic
Spin by a local detailer or autobody shop if you don't have a lot of supplies or if you want an experienced eye.
If you want to have a go at it yourself, an excellent over the counter medium-heavy polish that can work out defects pretty well by hand is Meguiars Ultimate Compound. It's around $10 at Wal-mart. Don't worry, it's not your old-school Turtle Wax gravel-style compound, it's slightly less aggressive than Meguiars 105, if you've ever used that cutter before. Wad up a soft cloth, rub a dot of that compound in with firm pressure, looking through the polish to check your progress. Lighten your pressure as you work it out. It will finish out pretty glossy by hand. You may need to repeat that a few times until you are satisfied with it. If that does the trick, followup with a mild polish or cleaner wax to finish out any hazing or micromarring left by the compound. If you have it, Menzerna Super Intensive Polish is a great mid-level polish for Bimmer paint. I'll usually start there with a defect like that and go either heavier or lighter depending on the initial result. |
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07-20-2010, 11:10 PM | #7 | |
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from that statement, and not being able to see it in the picture at all, I would think it was sanding scratches, which have to be removed with a rotary or something like meguiars 105 and a PC with an orange pad... |
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07-21-2010, 02:40 AM | #8 | |
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Paint Removed by Polishing When an abrasive polish works on the surface of paint it uses aluminium oxide spheres, suspended in an oil / water emulsion that provides surface lubrication, and uses a mechanical process to abrade the surface of the paint down to the level of the bottom of the scratch. Experience will teach you how your polish/pad combination ‘feels’ as it goes through the various stages; i.e. cutting, to polishing stage and finishing stages, just when the polish lubrication has dried up (this is usually when a polish starts to produce ‘dust’), this is where you stop, wipe off the polished area, inspect the paint surface and either clean the pad, apply more polish or change it for a clean fresh one. Using a medium abrasive polish and a rotary polisher will remove approximately 0. 1 Mil (3µ ) Range 0.8 – 1.1 Mil (20 – 28 µ) from the paint surface (typically 4 passes at 1500-1800 RPM) but there are many variables such as the abrasive grade of the polish or compound and speed and pressure used that may affect the paint removed) These numbers should be checked with a paint thickness gauge (PTG) There comes a point when you must judge wither removing a scratch will compromise the clear coat and if so you’ll have to ‘live’ with the imperfection. A clear coat thickness is approx 2-3 Mils (50 - 75 µ) a paint thickness reading of 4 Mil < ( 100 µ (Microns) is reasonably safe for polishing. 3 – 3.5 Mil ( 80-90 µ) I wouldn't use anything stronger than > 2000 grit polish, 2.75 – 3.0 Mil (70-80 µ) > 2500 grit polish and under 2.75 Mil (70 µ) use a glaze. If you have reservations about the amount of paint surface removed or the amount of paint coating remaining the use of a paint thickness gauge (PTG) is arbitrary Note: 1 µ (micron) is 1/1000th of a millimetre or 0.0393700787 Mil or 0.001 of an inch • 200µ 8 mil + can be expected on older cars that have been hand painted or a re-painted vehicle • 100 – 200µ 4 – 8 mil - normal paint thickness • 80 – 100 µ - 3 – 4 mils, thin paint • 80 µ < - less than 3 mil, very thin paint These numbers are offered as a guide only, as there are too many variables to provide any more than an approximation. Paint thickness will often depend upon the OEM paint specification, which can vary by vehicle assembly plant. It’s interesting to note that painters must now demonstrate proficiency with an electronic paint thickness gauge (PTG) in order to become certified to perform paint refinish warranty work for General Motors Corp. (GM) vehicles. |
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07-21-2010, 06:22 AM | #9 |
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Thanks again guys.
Is the fact that it's not visible from some angles a good sign that it's not through the clear coat? I am assuming that if you went through the clear it would not look glossy, or is that incorrect? My only fear is making it worse. I really appreciate the advice. |
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07-21-2010, 04:25 PM | #10 | |
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If you try to polish it by hand or with a random orbital machine, there's not much chance of making it worse. I would stay away from rotarys and direct drive buffers though.
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07-21-2010, 09:00 PM | #11 |
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Agree with Blackjack's post, let us know where you are
Gotta be someone in the area to have a look at it.
It really sounds like a touchup that someone sanded out but didn't get fully polished out, especially if it is cross-hatched, that's a pretty purposeful pattern. |
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07-22-2010, 10:15 PM | #12 |
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Funny, when I read a post like the OP's, I'm just dying to grab the Flex and slap a green pad on it with some SIP and have at it....it hasn't let me down yet!
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07-23-2010, 07:28 AM | #14 |
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Thanks a ton for the offer.
I'm in northeast Florida. I haven't got in touch with any local detailers yet because around here it seems like anyone with a hose and bucket calls themselves a detailer. (far fewer high end cars I guess means way less high end detailers) Seems like every time I take my car anywhere for anything (tires, tint, service...) I get burned, so I'm kind of wary. Any recommendations would be awesome. Last edited by wolfe; 07-24-2010 at 05:40 AM.. |
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08-01-2010, 03:44 PM | #15 |
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Hell yeah!
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