Brian_Brice
New member
David Fermani said:
Why go straight with wetsanding when you have zero clue on how deep it is till you give it a shot? Last case scenario wetsand IMO, and that's if it is bothering you that bad.
Need help from a pro!
- Thread starter popsinc
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Why go straight with wetsanding when you have zero clue on how deep it is till you give it a shot? Last case scenario wetsand IMO, and that's if it is bothering you that bad.
imported_Grouse
New member
David Fermani said:
I agree, I have done quite a bit of testing and measuring of scratch removal by rotary versus wetsand then polish.
Usually i find if the scratch can not be removed with a yellow foam pad (LC CCS/Edge) and reasonable work time (not re working the spot) along with a good polish SIP/PG it will likely be faster and remove less paint to wet sand.
In my personal testing Wet sanding will often remove just enough paint that it trips just outside of my PDM margin of error +-0.03%. Where as using a buffer will often remove 3-4 times as much clear in a much larger area, along with Heating the paint up in that area. sometimes to un acceptable levels.
David Fermani
Forza Auto Salon
Most of the *true* acid rain damage that I've seen and repaired (mostly on relatively brand new vehicles repaired under warranty) required wet-sanding. Very rarely did I opt to compound it. 2400 or even 3200 grit can do wonders rather quickly and easily. If there were very light/small ringlets barely noticeable, you could sometimes get away with compounding. After an acid bath of course. It definately wouldn't hurt to try/test whatever method to be sure if before doing the whole panel or vehicle.
I've always found it a PITA to remove acid rain and/or some overspray via a buffer. You're constantly required to check the buffed surface to make sure the problem is gone. With sanding, you can see your results "real time" by the marks your creating. I guess I'm just a big fan of light sanding. :nixweiss
I've always found it a PITA to remove acid rain and/or some overspray via a buffer. You're constantly required to check the buffed surface to make sure the problem is gone. With sanding, you can see your results "real time" by the marks your creating. I guess I'm just a big fan of light sanding. :nixweiss
imported_JoshVette
New member
VaSuperShine said:
+1
I totally agree with this. Wetsanding is a last resort in all situations. If it doesn't come out with the rotary, then wetsand it, either way it's a job for a pro.
Brian_Brice
New member
JoshVette said:
Precisely, I think that's a body shop route, many times I have listened to my clients tell me the horrible stories of how their body guys sand out anything they were unhappy with. Then again they don't polish it down. IMO it's just a nasty way to go right off the bat:nixweiss each his own I suppose.
David Fermani
Forza Auto Salon
JoshVette said:
Sorry if this is coming off :argue . Without trying to totally change subjects and go off on too much of a tangent, this may not be the most realistic blanket statement with "all" problems. Especially with overspray removals. When doing alot of heavy removals, it's much easier, faster and safer to use something like 4000 grit instead of compound or even an aggressive clay. Buffing would be the last thing I'd do, but it could be the best for others. I've had jobs where several companies were contracted to remove overspray & fallout from 100's of vehicles. I always wondered why we got them done correctly the quickest. Some shops took days longer than us.
If acid rain etching is obvious enough to be easily seen without magnification (especially after an acid bath), chances are you'll need to sand.
Brian_Brice
New member
David Fermani said:
I thought you gave someone that huge overspray job? Why use 4k grit when you could use a polish that's of the same abrasive level? It's much easier to take paint off an edge with sandpaper than it is with a lubricating polish, this whole paragraph seems a little body shop.
Accumulator
Well-known member
It seems like compounding/etc. often follows the depressions/contours of the etching whereas wetsanding only cuts the paint that's *higher* than those depressions. It's my opinion that *that* is why wetsanding with 3-4K and then polishing often results in less overall clearcoat removal.
imported_Grouse
New member
Well let me put it to you this way.
Gmc pick up hood.
Thickness readings on either side of the 10" scratch were 8.7-8.9 220-226 microns.
Taking one half of the scratch to be fixed with 2500 grit then polished ip green edge then 106blue edge, The other to be removed with PGyellow, Then IPgreen then 106blue
The measurements were fairly consistent along the scratch. 8.7-8.9 before work.
The side with the wetsanding and polish was 8.6 and 8.7 after finishing down.Total radius of work was 2" Meaning we removed that much paint on a 2" with
The side with the polish only was 8.3 -8.5 with areas of the scratch still showing. Total radius of the work was between 4-5 inches wide.
So we asked our selves how come the scratch was still there when we removed more paint than wet sanding. In simple logic it should be gone. But every action has a consequence. Because the polish had more lubrication and the same level of abrasiveness. it would continue to polish the valley of the scratch. Polishes will have a tendency to fill the scratch and polish the inside of the scratch while being worked. This was later affirmed by hitting the scratch with 3k sand paper and the polishing out with 106 and green LC pad. Removing enough paint to be with in the margin of error on my dft paint meter.
I have repeated this test a few times since. It always plays out that there is a certain point in marring where 3-4k sand paper Dry or wet will generally remove less paint overall than a polish. When you follow some basic rules ie 1/2 inch from all edges, proper lubrication and good sanding practices i personally think it can be much more effective than 3-4 stepping a car. In general if i have to 3 step a car IE PG yellow/wool, sip green, 106 white i will look at sanding the heaviest areas first.
My 2 cents in a world of 20 dollar bills.
Gmc pick up hood.
Thickness readings on either side of the 10" scratch were 8.7-8.9 220-226 microns.
Taking one half of the scratch to be fixed with 2500 grit then polished ip green edge then 106blue edge, The other to be removed with PGyellow, Then IPgreen then 106blue
The measurements were fairly consistent along the scratch. 8.7-8.9 before work.
The side with the wetsanding and polish was 8.6 and 8.7 after finishing down.Total radius of work was 2" Meaning we removed that much paint on a 2" with
The side with the polish only was 8.3 -8.5 with areas of the scratch still showing. Total radius of the work was between 4-5 inches wide.
So we asked our selves how come the scratch was still there when we removed more paint than wet sanding. In simple logic it should be gone. But every action has a consequence. Because the polish had more lubrication and the same level of abrasiveness. it would continue to polish the valley of the scratch. Polishes will have a tendency to fill the scratch and polish the inside of the scratch while being worked. This was later affirmed by hitting the scratch with 3k sand paper and the polishing out with 106 and green LC pad. Removing enough paint to be with in the margin of error on my dft paint meter.
I have repeated this test a few times since. It always plays out that there is a certain point in marring where 3-4k sand paper Dry or wet will generally remove less paint overall than a polish. When you follow some basic rules ie 1/2 inch from all edges, proper lubrication and good sanding practices i personally think it can be much more effective than 3-4 stepping a car. In general if i have to 3 step a car IE PG yellow/wool, sip green, 106 white i will look at sanding the heaviest areas first.
My 2 cents in a world of 20 dollar bills.
imported_Grouse
New member
Accumulator said:
exactly the conclusion i arrived at.
Brian_Brice
New member
Grouse said:
Strange findings, but make sense, definitely not universal code for all cases and situations.
David Fermani
Forza Auto Salon
VaSuperShine said:
That "huge" overspray job I posted about recently only consisted of about 30 vehicles. I was only to inspect/appraise them because they were part of my current day-to-day job (Auto Appraiser). I wasn't allowed to touch any of them because of the conflict of interest and I'd loose my job. Prior to doing this this work, I owned a detail shop in Michigan for 10 years where we did alot of heavy paint repairs such as overspray and fallout removal jobs in addition to paint warranty work for about 15 new car dealerships. Because I was in Michigan, there was alot of industrial manufacturing plants (auto related and non) and they regularly had smoke stack explosions and/or cleanings that contaminated 100's and sometimes 1000's of vehicles. Those jobs are what I consider huge. Most of the time when doing these types of jobs, 3200 and/or 4000 grit was the best way to correct the problem; followed by *light* polishing. When someone brought their vehicle(new or used) in because of a paint defect, the dealership (Body Shop/Service Department) sent them to us.
I was planning on giving Todd a sample of the 4000 grit paper when you guys come down next (Cavalino?) so you could try it out. Using this paper is totally unlike a 4000 grit polish(very little and different cutting properties), because of the way it quickly removes the problem. Plus, I've never seen or heard anyone removing too much paint with this paper either. It's pretty user friendly if used right. I'd compare it's cutting properties to very agressive clay, but just a touch stronger if you want it to. Plus, it can be used dry or wet for different applications and levels of cut.
Brian_Brice
New member
Gottcha, thanks for the explanation.
jimmybuffit
That'll buff right out!
Interesting thread. I think I learned something!
We've been using Mirka's Abralon sanding discs for a few years now, but y'all have shown me a whole new reason to use 'paper'.
Thank you.
We've been using Mirka's Abralon sanding discs for a few years now, but y'all have shown me a whole new reason to use 'paper'.
Thank you.
Todd@RUPES
Just a regular guy
I agree with this statement 100 percent. I will even take it a step further and saying that this applies to polishing as well. I have seen (by reading paint similar to what you did) that hitting the paint "hard" with an aggressive compound and then the requiste finishing removed far less paint then trying to finesse the scratch out.
You cannot polish away orange peel (highs and lows) because the pad isn't solid. When you buff, to an extent, you are buffing the highs and lows and chasing the scratch depth down. Sometimes (often) its better to go ahead and relevel the paint, then finish it back up.
Accumulator
Well-known member
Jimmy Buffit said:
Would the paper really be functionally different from the Mirka discs? It's the Mirka discs that my painter is trying to get me to use (when he says to wetsand instead of aggressively compound).
I get it that the discs have a foam backing, which is less rigid than most materials used with paper, but still...
I have yet another beater project lined up, a trashed Audi no less, when (heh heh, no not "if" :chuckle: ) I finally get the M3 outta here and I just might try sanding it :think: