First Time Attempting Wetsanding. Have Questions, Need Help (Pics Inside)

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<span style="font-size:18px;"><span style="color:#ff0000;">EDIT: Paint was corrected without wetsanding. Scroll down to post #10 to see how I corrected this. 


 


Hello all. I've compounded with success on several cars over the past 10 years and now, I may need to wetsand my latest car. Since it'll be my first time, I'm looking for as much info as possible before I start and I'm in no rush to start. I'd like to gather info here until I feel comfortable. 


 


The Car: 


2010 Audi S4. Repainted front end due to rock chips. Bad paint job is developing shrinks. No reflection whatsoever on the hood and fenders due to shrinking. I've tried compounding with Meguiar's Ultra Cut Compound #105 and a Griot's Garage DA which helped but didn't alleviate the problem.


 


The Plan:


I'm doing this is in the most conservative fashion possible. I plan to purchase foam backed Meguiar's Unigrit 3000 6" finishing discs and use it with a Griot's Garage DA orbital. Unfortunately I do not have a paint thickness device. I'm hoping since I'm using a DA and a conservative 3000 grit pad, on a repainted surface, paint thickness won't be an issue. After sanding, I will compound using the Meguar's compound mentioned above (#105), then polish with Menzerna High perfoemance polish (SI1500) then Menzerna Ultra finishing polish (SF4500).


 


My questions are:


1.) How many discs should I buy? What's the surface area a disc is typically good for? I'm doing the hood and fenders. 


2.) What chemical denotes the "wet" in wetsanding? Water?


3.) How many times over should I hit an area? ...or stay on an area?


 


Pics are below. ANY feedback appreciated. Thank you, 


 
<p style="margin-left:0px;">Fender is original paint, hood is clearly not (click thumbnail for hi-res pic).
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<p style="margin-left:0px;">Passenger fender:
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This is what I would do.  Your mileage will vary.


 


It would be a very good idea to do a small section from sanding to final polish to be sure you're doing everything right before attempting to do the whole job at once.


 


First, the goal of this kind of a top coat sanding is to match the existing orange peel - not to make the panels you're working on flatter and with more distinctness of image than the existing factory paint.  In this case, better is not better.  Invisible, no difference is better.  So, for the sanding part, you'll need 5 sheets each of 2000 - 2500 - 3000 grit sandpaper that's been soaked in water with a touch of dishwashing liquid for at least twelve hours.  A soft, not medium, not hard -  a soft sanding pad.  A rubber squeegee.  A quart spray bottle. Car washing gear.  


 


Wash the whole car and clay if there's contamination on the paint.  Contamination between the paper and paint gouges and scratches deeper than the grit of the various papers.  Dry the car.  Put a couple of table spoons full of rinse free wash and wax in a quart spray bottle to use as your sanding medium.  This keeps the sanding residue from sticking back down to the paint and makes cleaning up easier. Get your bucket with your soaked sandpaper and start sanding lightly with the 2000 grit paper wrapped around the soft pad until the paint looses its shine.  You can see when you're done by using your squeegee to remove the rinse free wash and wax.  The paint doesn't have to be absolutely dull, a few shiny dots are OK, and you might want to stay a quarter of an inch away from your edges unless you feel confident you can cut that close with your machines or are willing to do those edges by hand.   When you've done that, go to the 2500 and do it again.  Just be careful to hit all the paint you sanded with the 2000.  Then do the same thing with the 3000.    


 


Once the sanding is done you need to remove your sandpaper scratch.  Really, 3000 grit is more of a scuff than a real scratch and should polish out very easily.  Typically, people have problems getting sandpaper scratch out when they start with 1000 grit paper and then don't cut to the bottom of their initial cut with the following papers.  It's all about refining the initial scratch down to a true 3000 grit scratch.


 


BTW, the first cut is the one that defines the over all finish.  To cut seriously flat - perfect distinctness of image with no wave - you have to start with a very hard block and 800 to 1000 grit sandpaper depending on the hardness of the paint.  Harder paint will make paper mimic the orange peel so you have to start with sharper - more aggressive paper.  800 grit is, for me, reserved for the very highest end cut and polish jobs where the painter has put enough clear on the car to sacrifice a fair amount in the interest of being able to cut that aggressively.  


 


In this case, you're trying to preserve enough orange peel to match the existing paint.  That's why 2000 and the soft pad is the suggested starting point.  If you find that even this cuts too flat - remember my advice to do small section start to finish - skip the 2000 grit and start directly with the 2500.  


 


When it comes to polishing - I start with a rotary polisher  (Hitachi SP18VA) with a foamed wool pad and cutting/polishing compound to remove the sandpaper scratches.   Then I use a Makita BO6040 true dual action - gear driven rotation and an additional orbital movement - with a foam pad and polish - no filler - no glaze - to remove the swirls left behind by my rotary.   In my experience, it's much faster to cut sandpaper scratch with the rotary and then deal with the swirls than to try and do everything with any of the random orbitals.  


 


Since you don't have a rotary and I doubt very seriously you're interested in learning to run one for just this one job, I suggest you ask someone else on the board to tell you how you should remove your sandpaper scratch.  


 


All the best,


Robert
 
3000 grit comes out with microfiber pad and either D300 or M100 pretty easily (depending on hardness of clear)  M105 and surbuf will do it as well, but will madate an additional clean up step. But if you are sanding, and you want best results, I would plan on 4 stepping the car. - sand, heavy compound, light compound, medium polish, final polish.  There is no way you can achieve best results with just two steps (I've tried it, not good enough)


 


I would also recommend starting with 3000 on a DA and see where that gets you...just make sure to take your time and do it right instead of trying to blaze through it.  a 3" disc on a 3" backing plate with an interface pad will make the job a whole lot easier and potentially faster
 
@WhyteWizard , amazing write up and that helps out tremendously. You mentioned a block...so you suggest doing it by hand versus DA?


 


@Envious Eric: 


I definitely will do it in 4 stages. What do you mean when you say "3000 grit comes out with microfiber pad and either D300 or M100 pretty easily"? 


 


Thanks guys
 
The Meguiar's 3000 grit Finishing discs aren't meant to level paint...no point in starting with these IMO.
 
I ended up using CarPro's denim orange peel removal pads and WOW! The orange peel is gone and the reflection is restored. Pics to come once I get the rest of the car cleaned up and a nice day. 
 
Ok, here are the pics...I would like to thank David Fermani for first suggesting these. After some search, I decided to try it out. I still have a question regarding the last pic down...question is above the pic. 


 


I used Griot's Garage random orbital with Menzerna FG400 then finished with Menzerna ultra finishing polish 1500. I used 5.25" CarPro denim orange peel pads starting with the 1 setting to spread product around them moving up to 6. I bought 3 pads for this job. My only complaint was they caked up pretty fast and loses their effectiveness once they're caked up. A very, very mild complaint considering how AWESOME they worked. They may have caked up fast due to me using too much product so this may have been my fault. After cleaning the pads with a clean toothbrush and warm water, I let them dry and resumed the job the next day. I tried to resume the job sooner but I learned when they're not completely dry, they sling product/water everywhere.  Guess this is standard with any type of pad though. On to the after pics......


 


BEFORE:


 

upload pics
 
AFTER:


adult photo hosting
 


free jpeg images
 
Question about the pic below....as you can see, I didn't do the edges (bottom and towards the windshield). You can clearly see the dull areas towards the bottom and by the windshield. I was being cautious and trying to keep the edge of the pad away from corners. Any advice appreciated. 


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Your car looks great! I am curious to the actual process you used with the suggestions that came through. Did you use those Denim Orange Peel pads in place of wetsanding then? I am going to be picking up a DA this weekend most likely to tackle some imperfections on my truck. I am curious to know what all steps you went through cause you car looks amazing. Pardon my ignorance. I am pretty new to the world or detailing and paint correction.
 
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