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idickers
01-22-2012, 02:00 PM
I've just picked up a 1991 BMW 318is, which has its original silver metallic paint that has been well and truly beat. The paint is oxidized and the clearcoat has scratches. I plan to fix the mechanicals and some rust over the next year, and then repaint the car myself. However, I thought the current paint would be good to learn some polishing/sanding techniques prior to working on new paint.

What is the best method to attack an old finish? I have in my garage a Dewalt DW847 7" rotary polisher (0-1750 rpm), a Porter Cable 7336SP random orbital polisher, and a lot of interest on my part, but very little practical knowledge. Is this something that is best started with wet sanding, or can I start with a buffing compound?
Thanks for any suggestions,
Ian

style
01-22-2012, 05:12 PM
I've just picked up a 1991 BMW 318is, which has its original silver metallic paint that has been well and truly beat. The paint is oxidized and the clearcoat has scratches. I plan to fix the mechanicals and some rust over the next year, and then repaint the car myself. However, I thought the current paint would be good to learn some polishing/sanding techniques prior to working on new paint.

What is the best method to attack an old finish? I have in my garage a Dewalt DW847 7" rotary polisher (0-1750 rpm), a Porter Cable 7336SP random orbital polisher, and a lot of interest on my part, but very little practical knowledge. Is this something that is best started with wet sanding, or can I start with a buffing compound?
Thanks for any suggestions,
Ian

Go pick up some 1500 and some compound and try leveling the paint with 1500 wet with share block then Polish out the scratches with a wool pad and compound once you can get the scratch out perfect then hit it with a black foam and the same compound then once you have that all down pick up some sure finish and you'll be set..

tomsteve
01-22-2012, 06:15 PM
i would suggest that before doing anything,wash it good, then clay it. some pics would help determine the best coarse of action to take.

idickers
01-26-2012, 12:21 PM
For wet sanding I think I'm going to get an Airvantage sander. For buffing, would I be better off (as a beginner) using the random orbital polisher, or the rotary?

Len
01-26-2012, 01:08 PM
For wet sanding I think I'm going to get an Airvantage sander. For buffing, would I be better off (as a beginner) using the random orbital polisher, or the rotary?

Get a decent variable speed rotary, it's the only way you're going to make any progress in a reasonable length of time. If you're scared of damaging the paint you can slow the rotation.

idickers
01-26-2012, 01:19 PM
My Dewalt is variable speed (0-1750 rpm), will that do?

Len
01-26-2012, 02:10 PM
My Dewalt is variable speed (0-1750 rpm), will that do?

Yes, that will probably be fine. Get the right backing plate, pads and compound if you don't already have them.


http://autobodystore.net/Merchant2/graphics/00000001/sfstuff.jpg
LINK (http://autobodystore.net/Merchant2/merchant.mvc?Screen=PROD&Store_Code=ABS&Product_Code=SFPADS&Category_Code=T2)

idickers
02-05-2012, 02:52 PM
Here are some pics of the paint. I can't feel the scratches when I run my fingers over them. It looks like the previous owner never waxed the car, and washed the car with a scotchbrite pad.
Ian
84298430

idickers
08-16-2012, 05:42 AM
I bought some Sure Finish, the set of Sure Finish polishing pads,and Robert's "Detailing for Enthusiasts" DVD. From watching Robert's video, it looks like I should start out using Sure Finish on a wool pad on the rotary polisher to remove scratches, and then switch to a foam pad on my random orbital polisher to remove swirls.

The polishing pad kit comes with two wool pads, a high density and a loose, and with two foam pads, black and orange. How should I decide which wool pad to use, and then which foam pad to follow-up with?

Len
08-16-2012, 07:15 AM
I bought some Sure Finish, the set of Sure Finish polishing pads,and Robert's "Detailing for Enthusiasts" DVD. From watching Robert's video, it looks like I should start out using Sure Finish on a wool pad on the rotary polisher to remove scratches, and then switch to a foam pad on my random orbital polisher to remove swirls.

The polishing pad kit comes with two wool pads, a high density and a loose, and with two foam pads, black and orange. How should I decide which wool pad to use, and then which foam pad to follow-up with?

Just about any standard wool pad will work and I'm a big fan of the orange foam pad for almost any application. The problem I see when looking at the picture is that the clear has "crazed" (cracked) and I doubt that you're going to be able to remove a lot of the damage by buffing but you may be able to get rid of some of the cracks by sanding and polishing.

idickers
08-16-2012, 08:20 AM
Thanks for the quick help. I'd like to work on this over the weekend, and don't have an air sander. Can I pick up some sandpaper form a local auto paint supplier and use my random orbital polisher/sander, or should I do this by hand?

Len
08-16-2012, 10:04 AM
Thanks for the quick help. I'd like to work on this over the weekend, and don't have an air sander. Can I pick up some sandpaper form a local auto paint supplier and use my random orbital polisher/sander, or should I do this by hand?

I'd recommend picking up some 1500 or 2000 grit wet sanding paper and doing it by hand. You can get "Job Packs" of 3M sandpaper with 5 sheets of paper. Put a couple sheets in a bucked of water and let them soak about 15 or more minutes before you use them. Sand a small 2 square foot area then polish it to test your result before sanding the entire car, you may find that it won't help enough to make it worthwhile.


9812
Job Pack Link (http://autobodystore.net/Merchant2/merchant.mvc?Screen=PROD&Store_Code=ABS&Product_Code=3mimpwetdry&Category_Code=SM)

9813
Link (http://autobodystore.net/Merchant2/merchant.mvc?Screen=PROD&Store_Code=ABS&Product_Code=3m5526&Category_Code=T)

Henry
08-16-2012, 10:48 AM
Thanks for the quick help. I'd like to work on this over the weekend, and don't have an air sander. Can I pick up some sandpaper form a local auto paint supplier and use my random orbital polisher/sander, or should I do this by hand?

OEM paint does not allow for very much sanding at all let alone paint from 1991. Below is a LINK to Robert doing a sand and buff on OEM paint and remember, Robert is a highly skilled professional in doing this. I would guess you will go right through your clear into the silver and have a mess because of sanding. ROBERT'S EFFORTS:

http://www.autobodystore.com/rsw.shtml

This link comes from the CLASSROOM which can be found from the HOME page at the top left of any page you are on. You will find tons of information there.

Henry

edit added: It's important that you "season" the wool pad with a little water and product. Don't hit that old paint with a dry wool pad. I prefer Robert's ORANGE pad.

TOGWT
08-17-2012, 03:14 AM
A question before you wet-sand or compound/polish the paint surface-

What paint thickness do you have to work with?

idickers
08-17-2012, 06:35 AM
I'm not sure. How would I tell? I'm pretty sure it's 20 year-old original paint, that didn't receive much care.

Henry
08-17-2012, 10:30 AM
I'm not sure. How would I tell? I'm pretty sure it's 20 year-old original paint, that didn't receive much care.

No need for you to sand for a shine and no need to. I say if you sand your paint you'll break through the clear quicker than a HO BO on a ham sandwich.

If the surface is longtime dirty then you need to wash it first to get at the paint. I use BLECH-WHITE tire clearner you can use Dawn for dishes. So, clean it well then move on to buffing with the product you have.

Henry

Len
08-17-2012, 10:58 AM
No need for you to sand for a shine and no need to. I say if you sand your paint you'll break through the clear quicker than a HO BO on a ham sandwich.

If the surface is longtime dirty then you need to wash it first to get at the paint. I use BLECH-WHITE tire clearner you can use Dawn for dishes. So, clean it well then move on to buffing with the product you have.

Henry

Dirt and dullness doesn't seem to be the problem. It appears that the paint is checked and only washing and buffing is probably going to do little to correct it. I'd recommend sanding and buffing a test area to see if it helps and if it doesn't then you're going to need a paint job to correct the problem.

idickers
08-18-2012, 01:03 PM
Thanks for all the helpful suggestions. Unfortunately, it looks like the paint is well and truly trashed. I tried New Finish with a wool pad on the rotary polisher, followed by an orange pad on the random orbital, but didn't get rid of any scratches. I sanded with 1500 wet, and got a dull haze, and repeated the wool pad/orange pad, but still had scratches below the surface.

I learned a lot, and am no longer afraid of the rotary polisher :D, but it looks like for this car we need to save up our lunch money for a paint job.

Len
08-18-2012, 02:20 PM
Thanks for all the helpful suggestions. Unfortunately, it looks like the paint is well and truly trashed. I tried New Finish with a wool pad on the rotary polisher, followed by an orange pad on the random orbital, but didn't get rid of any scratches. I sanded with 1500 wet, and got a dull haze, and repeated the wool pad/orange pad, but still had scratches below the surface.

I learned a lot, and am no longer afraid of the rotary polisher :D, but it looks like for this car we need to save up our lunch money for a paint job.

That's what I was afraid of, the paint is cracked and the cracks go all the way through the clear so sanding and polishing usually won't correct the problem. The best method to correct the problem is to remove the paint and apply new paint. You may get away without stripping by prepping, priming and painting on top of the existing finish but those hidden cracks could come back to haunt you.

s class
08-18-2012, 03:04 PM
What causes this kind of paint damage - sun?, lack of waxing?, what?

Len
08-18-2012, 03:09 PM
What causes this kind of paint damage - sun?, lack of waxing?, what?

I'm not sure about ALL products but some clear tends to tighten and get brittle as it ages causing this type of problem. This is one of my main reasons for purchasing high-end clear for most of my work. They all look the same coming out of the gun, it's the aging process (and a few other things) that separates cheap from good paint products.