Thinning the Clearcoat

[Accumulator]

This topic comes up from time to time and I *usually* tell people not to worry about it. But OTOH I leave marring in my "keepers" because I`d usually rather have imperfect looks than risk a repaint.



Having recently purchased an ETG (which I haven`t used yet) and having a *really* pitted/etched/scratched car to do when if finish the M3 (which I`m just rotarying to *death* in an effort to fix scratches), I`ve been pondering the "taking off too much clear" issue. If I kill the M3 I`ll get over it as I`ll either sell it anyhow (likely) or get it repainted if I keep it (less likely). But I sure don`t want to over-correct anything I`m keeping, so a few thoughts follow and I`d appreciate any comments:



I ran across a thread where RAG did some ETG testing with various combos. He found that to completely remove 2K sanding scratches he had to do two passes with rotary/black Edge wool/HTEC-OPmix. Tested independently of the 2K sanding, said combo removed ~7 microns of clear with *one* pass. (each "pass" was about four strokes back/forth, enough to properly work the product.) That means he removed ~14 microns of clear to remove those sanding scratches.



14 microns = ~.34 mil which is right around ~1/3 mil that`s recommended as the max clear you can remove before you precipitate clearcoat failure. Some people think you can take off up to 1/2 mil, but even then that`s over the entire life of the paintjob. And all this is leaving out the clear removed prior to the correction by the wetsanding and any subsequent final polishing with milder combos.



So how to do serious correction (uh-oh...like what I`m doing on the M3 :nervous: ) without long-term consequences?

[Finaltheorem47]

uh oh... wish I read this before wet sanding my car today...

[Invigor]

sand `er down, polish `er up. Then X-Kote!



I speak the truth!

[ALAN81]

Do you really have 17,990 posts .......................WOW

[JonP]

Do you really have 17,990 posts .......................WOW

Makes you wonder how he actually gets anything done.:hm

[asleepz]

I`m not a pro, but I`d say if you don`t want to do a repaint, do what you can and keep a close eye on the paint thickness (if you have a gauge) and just keep it protected very well and do everything possible to prevent any more marring or scratches. Such as never driving it or keeping it in a sealed bag lol. Sounds like if you are that worried about it, do what you suggested, sell it or repaint.



I don`t belive you would experience clear coat failure within 4 years of an autopian taking care of it, after that or when convenient, sell it. Cold hearted to say, but after it`s gone no more worries about paint failure. It`d be someone else`s problem.

[getcha]

If I kill the M3 I`ll get over it as I`ll either sell it anyhow (likely) or get it repainted if I keep it (less likely).

Accum this makes it sound like if you butcher the car by accident its ok because the next guy will get it

[David Fermani]

Accumulator - The level of reduction needed will obviously be dependent on the problem you`re trying & willing to address. A pitting condition can and usually is a serious problem that requires a substantial amount of leveling to correct. I`d strongly suggest that you test out several areas with several different products to see what it actually takes to get you to your acceptable correction. If possible, I`d avoid 2000 grit and go with maybe a Trizat 3000 or even a 4000 grit paper instead. That way, less passes with less agressive compound will be needed and you`ll remove less paint in the long run. Cutting/sanding more controlled amounts would be much more effective than the immediate quick cut of 2000 grit papers followed by a heavy compound IMHO.

Good Luck.

[Stanger'66]

I wouldn`t really worry about it. It is all dependent on the particular car anyway. Maybe I am not as concerned since I also paint, I don`t know. After painting the car usually goes through a pretty thorough cut and buff which removes a good amount of clear. The cars never have problems. Of course these are custom jobs that are meant to be cut and buffed but still, how thin of a clearcoat can the factory be applying? I wouldn`t try to sand out all the OP but a little defect removal is just fine IMO. Personally I am more concerned with the rock chip damage. This alone is going to cause a repaint of 3 panels for me...

Grant

[imported_Dave1]

But I sure don`t want to over-correct anything I`m keeping, so a few thoughts follow and I`d appreciate any comments:



I ran across a thread where RAG did some ETG testing with various combos. He found that to completely remove 2K sanding scratches he had to do two passes with rotary/black Edge wool/HTEC-OPmix. Tested independently of the 2K sanding, said combo removed ~7 microns of clear with *one* pass. (each "pass" was about four strokes back/forth, enough to properly work the product.) That means he removed ~14 microns of clear to remove those sanding scratches.



14 microns = ~.34 mil which is right around ~1/3 mil that`s recommended as the max clear you can remove before you precipitate clearcoat failure. Some people think you can take off up to 1/2 mil, but even then that`s over the entire life of the paintjob. And all this is leaving out the clear removed prior to the correction by the wetsanding and any subsequent final polishing with milder combos.



So how to do serious correction (uh-oh...like what I`m doing on the M3 :nervous: ) without long-term consequences?

Good question......



I have a ETG II and used it to check the paint surface of my Acura after removing a bird bomb not long ago . The right front upper quarter had a nice yellow white turd bake in one day last summer..... It was a bad one. After cleaning it off, I saw the exterior ring that etched into the paint.

So, I first tried some Menz IP and and orange pad........nothing.

Then some Presta 1500 with a wool pad at about 1200 rpm........still there.

I finally got it out with some Presta UCC and wool with many many passes,........ it got warm, I checked it frequently.....



Needless to say, the entire panel has different readings from front to back. Reading in mills they ranged from 4.1 to 3.8 on the areas that were not worked on. The hood was all over the place because of a previous paint job repair years ago. The nose area of the hood had readings of 7.8 and as you work back to the center and near the windshield area the readings went down to the 4.2 and 4.4 range.....



For the area on the front quarter that was buffed with a wool pad many times, the readings were 3.7 to 3.6. A couple of inches away the readings are 3.8 and 3.9......



What does that mean.....?



For me, it means that many passes with twisted wool and Presta UCC followed up with foam pads and polish only removed about .1 to .2 mills.



A follow up study with some test panels might prove to be very interesting......:xyxthumbs

[Accumulator]

Accum this makes it sound like if you butcher the car by accident its ok because the next guy will get it

Well, IMO "butcher" is the wrong word. Nothing I do will make the car worse overall the way I see it, just make it vulnerable to UV damage over time. Sorry if my hyperbole made it sound like I was *really* messing it up...I meant relative to my good vehicles and I guess my wording was overly exaggerated.



I`m guessing you never saw any of my older posts about the cars original condition- when my painter saw it, he just shook his head and said "well, you gotta start with a 1500 (!) wetsand and go from there..". E.g., the repainted areas are simply awful, true amateur-hour work, scratches are nail-catching deep all over the car, the pitting is almost to the primer in places, the plastic panels were R&R`ed improperly and their clips are busted, etc. etc. It simply needs body/paint work instead of a "detail" and I have to decide if I`ll be the guy to "save" it; I`ve already spent a fortune on the mechanicals and done the (unspeakably filthy) undercarriage.



And I always exercise full disclosure when I sell something anyhow, so no subsequent owner will *ever* have any surprises that`re my fault Never.

Do you really have 17,990 posts..Makes you wonder how he actually gets anything done..

Heh heh, between the dogs and the house and doing the daily drivers and *all the posting here* I *don`t get a lot done...that`s why the M3 and some others are such long-term projects But seriously, I do my Autopia posting when I`m in my home office for one reason or another anyhow.

The level of reduction needed will obviously be dependent on the problem you`re trying & willing to address. A pitting condition can and usually is a serious problem that requires a substantial amount of leveling to correct. I`d strongly suggest that you test out several areas with several different products..

Yeah, once I realized the severity of the pitting (and the quality of the repaint work) I accepted that this one really needs fixed with a paintgun I`m gonna do some experimenting on some of the scratches when I level the touchups (that I couldn`t resist doing on the to-bare metal scratches and chips)...I have Meg`s/Nikken 2 & 3K, and some Mirka 2 and 4K, and also some other stuff I might experiment with. I`ll stop well short of really messing up



I simply don`t have to do much serious correction on the "good vehicles" so trying to do very aggressive work on something *really* messed up is a learning experience for me.

A follow up study with some test panels might prove to be very interesting......

Yeah, and I plan to do that. I don`t want to read *too* much into RAG`s experience, but he and I know each other well enough that I take his findings seriously and, well, they got me thinking.



Now that I have the ETG I`m gonna see what`s really going on, and I`ll post about what I learn. I just tossed this thread out there a little prematurely as I wondered what people might think about it.



Thanks for posting about *your* experience..it gives me a little extra optimism!



Before I start on the next big correction project, I want to have a better understanding of how much clear each process removes. Painting/thinning the M3 is one thing, but I don`t want to end up repainting every beater car I buy

[Spilchy]

If the M3 is garage kept with a nice coat of protection on it on a regular basis, then you should be okay. I base this on experience



I just sold my 12 year old Honda Civic that never saw a garage but wore Collinite 476s for most of it`s life and was polished twice a year. Outside of a little crazing on the hood, the paint was glossy and new looking as ever. All the mechanics at the shop wanted to buy it but not for my asking price! What the new owner will do with it, I don`t know. I *do* know it went to his 17 year old daughter which isn`t a good sign!



Also, I didn`t see what pad / product combos you were using in your "rotary death" sessions. I know you`re not really a heavy compound guy so maybe you`re over reacting since you haven`t even used the gauge!

[Accumulator]

If the M3 is garage kept with a nice coat of protection on it on a regular basis, then you should be okay. I base this on experience..

Yeah, I know..there are a scad of areas where the "reconditioning" guys cut the Blazer down to basecoat/primer and the thinned clear at the feathered edges holds up just fine given how I treat our vehicles (476S on that one too). Still...well, you know..and some colors, perhaps like this one, can fade without good UV protection.

Also, I didn`t see what pad / product combos you were using in your "rotary death" sessions. I know you`re not really a heavy compound guy so maybe you`re over reacting since you haven`t even used the gauge!

I didn`t break out the 3M ECRC or try wool pads (coulda/shoulda) but I did repeated (and I don`t mean just ten) passes with HT-EC/orange and yellow/speeds up to 2K. Hey, maybe I *am* worrying over nothing, but I`ll know for sure when I get that ETG outta the box and take some readings but some areas are getting that "too-light, no-depth" look under certain inspection lights that has, in the past, meant "thin clear".



This whole thread is sorta a case of my just thinking out loud



Off-topic- Did you take that trip to Israel? How`d it go?

[Spilchy]

Off-topic- Did you take that trip to Israel? How`d it go?

Oh man, what a trip. I traversed the country over a 10 day period with a private driver going to all the famous places and many, many out of the way, not so touristy spots. As a Jew, it was very spiritual, emotional and enlightening. I could write a book on it. I took 485 digital photos and if I have the mindset, will put together a nice photo montage with captions in the Hot Tub section.



I know you have an interest in weapons. I was able to hang out and survey up close, standard issue side arms and assault rifles for the police, a special forces police, army and special forces military units. Many had the M16 but a lot had Israeli made including the new Tavor which is replacing the M16 there. This weapon is sweet! YouTube - Tavor

[wannafbody]

I`d just use the 3m compound and a wool pad and go to town. If the paint is that bad you have nothing to lose.