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Reparing scratches

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  • Reparing scratches

    I know this is not exactly an HSM question but I'm continually astounded my the breath and the depth of knowledge that the members have on various topics.

    As you can see from the picture, I have a scratch on my car.

    How do I best repair this? More often than not, any touchup paint that I've seen looks worst after than before. If I get a matching paint, how do I best apply it and get it flush with the rest of the paint? Also, is buffing or polishing in order?

    Thanks for any advice.


  • #2
    We are looking at the grey primer under the paint in your picture, right?

    I have successfully repaired tons of scratches, and the technique depends on how perfect you want it to look. If you don't mind it being perceptible upon close examination, you can get away with using touch-up paint and a brush. I will post how I handle them this evening, as I am short on time right now.


    • #3
      You can steal some touch up paint from under the hood of your car with a paint brush and something that will dissolve the paint. Denatured alcohol on an artist's paint brush may work. Then just apply the paint you removed over to the scratched area after cleaning it thoroughly.


      • #4
        Try your touch-up paint 1st in a door jamb or someplace that's not seen easily to test the color match. If it's good, use a fine tipped artist's camel hair brush and a capful of lacquer thinner. Get one of those flip-up binocular magnifiers and a strong light so you can REALLY see what you're touching up. Dip the brush in the paint, then the thinner and carefully flow the paint into the scratch. Build up the thickness in several coats. You'll be surprised what a nice job you can do when you can see the scratch properly and the paint is thin enough to flow in nicely.

        "Accuracy is the sum total of your compensating mistakes."

        "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton


        • #5
          Thinning the paint will make it lighter. If this is an outdoor car where the paint has maybe faded, you can thin the touchup paint a little. We're talking drops here. Also, there's little chance of making a fix that won't show unless you blend it into the panel. You can't do that with a brush! If you just want to cover the primer and get it close, I need a little more info.

          1. What year/make is the vehicle?
          2. Is this original paint?


          • #6
            I drew a depiction of how to fix a scratch. This assumes your car has a clear coat over the paint. Most do nowdays.

            Here's what you'll need:
            Color touch-up paint.
            Clear touch-up paint.
            Wet & Dry Sandpaper (1000-1200)
            Bucket of water.
            3M squeege or small flat sanding block.

            1. Shows what a scratch looks like from the side. From bottom to top; Panel, Primer, Color Coat, Clear Coat. Wash the area with soap and water--ammonia soap works best. Let this dry. Make sure there's not dust or lint.

            2. Apply your color touch-up paint. Don't worry too much about "staying in the lines". You'll need to apply at least two coats. Wait about 10 minutes between coats. Let the paint dry about two hours.

            3. Use your block/squeege as a backer and lightly wet sand over the scratch. Use lots of water. Don't over sand in one spot. Take long strokes parallel to the scratch then lightly perpendicular. All you want to do is level the color you just put on. Rinse the area well and let dry. The sanded area will look foggy over the color and the original clear.

            4. Apply your clear coat touch-up. This may take two or more coats. This is the same as the color--don't worry about a perfect coat. Let the clear set about 15 minutes before applying the next coat. Let this dry overnight or a minimum of eight hours.

            5. Same sanding procedure as #3. The clear coat will be a little harder to sand but don't over work the area. Dry the area and look at the edges of the clear you put on. There should NOT be any shinny (dark) edges. If there are, it means the clear is still above the original clear. Keep sanding. Lightly! If you don't get it even, it WILL show when you buff it out.

            All that's left is to compound and polish the sanded area. I use 3M Heavy Duty compound. It's good for clear coat but watch that you don't burn through. It's easy to go right through the car's clear coat if you're not careful. Keep the buffer moving! All you want to do is level the sanding scratches and blend into the rest of the panel. Wait at least a few weeks before you use any polish that contains petroleum distillates. These will soften fresh paint and extend the curing time. (By Months!) I use soap-based compound and polish.


            • #7
              I usually do basically what Ken suggests, with only minor exceptions. If you have an artist type in the family with good eyes, consider letting them apply the paint.

              Usually, where a scratch starts or ends, there is a good bit of damage that is only on the surface. This area can simply be buffed or sanded out, so only apply paint where the scratch goes down to the primer.
              Make sure there is no wax in the scratch, use a toothbrush to clean the edges if necessary. Touch-up paint usually dries pretty quickly (stay out of the direct sun), so keep moving, and finish with a long smooth stroke if possible (sort of a 'dab it in there' - then make it smooth kind of thing). If you get this part wrong with metallic paint, it will be easier to see the repair.
              I find it easier to get good results if I keep the paint 'in-between the lines'. Be sure to fill (or rather, overfill) the whole scratch with the paint.
              A small block of wood (aprox. 3/4"x1 1/4") makes a great sanding block for this application. Let the paint dry thoroughly before sanding. Try to sand ONLY the scratch for as long as possible, as it is fairly easy to sand through the finish – at least until you get used to the process.
              Applying the clear coat can be considered optional. I have ignored this step with no discernable negative consequences, even with DBU paint.
              I use a finer compound than Ken does, usually 3M imperial Microfinish, but most anything will probably work fine.

              This process is faster and easier to do than it sounds. And remember, even a half way decent job will be imperceptible to anyone but yourself.


              • #8
                Thanks for all the tips. With all the good advice, I now have the confidence to try it, although I'll practice it on other painted sheet metal before attempting on my car.

                My car is year 2000, Saab 93 convertible (answer to mid-life crisis). The colour of the paint is metallic dark greeen, and it's original paint.

                My other question is, is buffing and polishing, both of which I believe involve very fine abrasive, worth doing? Am I removing more of the clear coat for sake of the looks, or would it actually help?

                Thanks again.



                • #9
                  You will have to buff out the sanding scratches around your repair. But in general, you usually only have to buff a whole car if there is oxidation of the finish (and yes, the buffing/polishing compounds are abrasive). This shouldn't be too much of a problem on a 2000 model vehicle if you ever wax it. You can certainly buff it out to a nicer finish and really make it shine, but then you will have to wash and wax it all the time to see the fruits of your labor!