View Full Version : Wet sanding and buffing
01-17-2006, 08:39 PM
I'm working on a black BC/CC finish, and i have wet sanded the clear with 1200. I purchsed the 3M extra cut polish, and I am trying to buff out the scratches with my Makita buffer. I'm just not having much success. It's taking a lot of effort to get out all of the sandpaper scratches.
I don't have a good DA, so I am doing it by hand. It's a fat fendered car, and there aren't namy flat surfaces. I'm a little nervous about using anything but elbow grease to sand it. Do I need to go over it with a finer grit? I sanded a small area with 1500 to see how that worked, but it still it tough getting the scratches out. The polish just doesn't seems to be "cutting" much of anything.
How often do I need to "fluff" my buffing pad? After you start working in the material, how long do you keep buffing an area? ....until all the material has disappeared? At what point is most of the cutting done?
01-17-2006, 09:18 PM
When I always cut and buf I always finish with 2500 grit. At the least I wouldnt go below 2000 grit. It just makes it easier because buffing isnt my favorite thing to do. With black you almost always have to end up using a orbital buffer with swirl remover to get it perfect. Sometimes just a swirl remover will work. Fluff your pad when there is build up. Hope this helps,
You're probably correct in wet sanding rather than using a machine if it's all rounded panels especially when you're not accustom to the job.
1200 may be a little coarse to try to polish out of hardened black/clear urethane, I'd recommend that you sand it with 2000 or even 2500. Be sure that you use a lot of water so that any particles (dust nibs in the paint or dirt) get washed away as you sand. Don't run the polisher at high speed, keep it at about 1000 rpm or less. Have the buffer contact the surface so that the rotation will take the pad along the curved surface NOT across the curve.
I haven't used that compound so I can't comment on it but I've had problem jobs that I've been able to cut quickly with the Sure Finish "Foamed Wool" pad and Sure Finish. The Foamed Wool Pad will hold a lot more compound on the surface and thereby cause a faster cutting action. It worked great with the Sure Finish so it may work with your compound. But first try sanding with some 2000 grit wet and use a sanding pad with plenty of water.
Ultra Fine Wet Sandpaper Link (http://autobodystore.net/Merchant2/merchant.mvc?Screen=CTGY&Category_Code=M3)
Sanding Pad Link (http://autobodystore.net/Merchant2/merchant.mvc?Screen=PROD&Product_Code=DRBAF4405&Category_Code=TFSL)
01-18-2006, 10:21 PM
Thanks for the advice.
I went back over the car with 1500 then 2000, but it's still taking an excessive amount of effort to bring the finish to a shine. It not like it's not removing random deep scratches. It's just tough getting out any scratches.
When I purchased the compound, the guy at the local supply house lead me to belive it was a very aggressive compound, so I ended up getting the 3M yellow wool polishing pad because he said it was "less aggressive". Could that be the root of the problem? Do I need a more aggressive pad?
01-18-2006, 11:08 PM
If you're going to use 3M, I'd suggest their 100% wool pad. Also, spray a little water on it and it'll cut a bit faster.
01-19-2006, 12:21 AM
Here is how i buff. I have a 3m cutting compound that produces a light swirl mark and a 3m machine glaze that removes swirl marks. I hard block the area with 1200-1500 depending how bad. I put a slight amount of soap in the water bucket to lube the sanding process. I sand and use a unused bondo spreader to wipe the area to see my process. Then I Use a 3m foam compounding pad with a few mist of water and use the cuting compound, then swith to the foam polishing pad and the machine glaze and mist the pad and I let the pad do the work I hold the buffer flat on the surface and let the pad do the work dont press to hard. If you want to get it extremly shiny they make some more glazes and waxes but for a repair you dont have to worry about that.
01-19-2006, 03:22 PM
Emphatically: Yes, you need a different pad. Trying to remove sanding scratches with a polishing pad is a waste of time and effort. A twisted wool compound pad will work way faster - I predict you will be amazed.
01-19-2006, 04:59 PM
I agree with mmooney84.... I have never sanded with finer than 1500. I get a beautiful finish and in no time. Just a few days ago I buffed some AE after sanding it with 1200. AE being soft, the 1200 is workable. With CC I use 1500 but still it looks great. So, I don''t think the paper is your problem. There is a definite technique to buffing. I used to use 3m Microfinishing compound. I was happy with the results, but now the Truefinish I use is more user friendly, thus a btter material. You need to work an area about 2' x 2'. You should apply just moderate pressure, move slowly and buff until the compound begins to disappear. I do this with wool. Then I switch to a foam pad and repete the steps. The Truefinish allows to to get the surface as is, not having to switch materials during the final stages. I buff with the foam until the compound does disappear. I can take a 1200 scratch on AE in a 2' X 2' area and have it almost perfect looking in about 45 seconds. Then switch to foam for another 45 seconds.
01-19-2006, 07:47 PM
Welcome back! We had to change the name to Sure Finish because True Finish was taken. Thanks for the note.
01-19-2006, 09:49 PM
You got my vote on the 'SureFinish' also. I think it is the greatest compound that I have every used.
Start with a wool pad, and then to the foam. I use the hook and loop pads, so they are easy to change back and forth as needed.
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01-19-2006, 11:49 PM
Pretty much any Polish worth it's price should take out 1500 and finer grit scratches. Having said that use one that is labeled to do so and not more aggressive than you need.
Wool pads are fine for heavy oxidation or really bad surface marring, but bear in mind that they are more aggressive (cut faster) than most foam pads so you need to be careful.
I use the method mentioned by others (stepping through the grits 1500-2500) and finish off the panels with my Dewalt 849 rotary starting with a light cut foam pad.
Use just enough polish to get the job done in a small (2' x 2' area). Usually a drop less than a quarter in size will do. Some polishes require some "pressure" to be initially applied when you start running the machine to aid in "breaking it down", after which you lighten up on the pressure.
When I've finished removing the sanding marks,swirls, whatever, I switch to a polishing pad with a light cut polish to both remove any halograms left by the light cutting process and to bring up the shine.
Over on Autopia.org (a website dedicated to detailing rather than autobody work) when someone describes the problems your having it's usually due to one of two things.
1) wrong pad/polish combination for the work at hand
2) wrong application technique.
Correct one or both of these issues and you'll be fine. Just go slow and check your work often
01-23-2006, 09:22 PM
Thanks for all the advice.
I'm done with the 3M compound. I'm having to go over everything 3 times, and it still won't remove all the scratches. With anything other than black, it would be fine, but as much time and money I have spent, I'm not going to let this go now.
I'm ordering the Surefinish.
01-23-2006, 10:43 PM
There is a number on the Surefinish label you can call if you want to ask any questions. I hear the guy that picks up the phone is pretty good.
01-31-2006, 04:00 PM
I just wanted to give an update.
I got my shipment of Surefinish yesterday, and i tried it out. I am really impressed with this stuff, and I wish that I had gotten it earlier. It only takes a small amount of polish to work a pretty large area. It doesn't dry up near as fast as the 3M, and it allows you to have more control. You can keep working a spot, and it allows you to see what you are doing. The other just dries up and turns to dust after a couple passes, and just like they said, you can just switch over to a waffle pad to remove the swirls and cobwebs.
I had already done most of the car with the 3M products - which consisted of at least 3 rounds with the "extra cut compound". I went over one of the front fenders with the Surefinish once with the wool pad and once with the waffle, and the difference is obvious.
01-31-2006, 11:06 PM
Glad to see you got things working out. Everyone who starts out polishing and buffing will go through a learning curve figuring out what works best for them in a given situation.
I've never used Sure Finish but it sounds like it has a decent "work time".
Polishes/compounds all "break down" at some point and that's when they begin to do thier work.
Using them too far past this point "when they start to dust" is counter productive and harmful as you will be running dry product against the panel and probaly adding more swirls then your taking out.
The key is knowing when to stop.
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