Surface Science: Car Scratches

Car Scratches in White Paint

As any driver knows, surface scratches plague the visual aesthetics of a car’s paint job. They make a paint finish look dull and neglected, and in some cases can cause the need for repainting. What most everyday drivers don’t know is that there is a science behind scratches, and removing them isn’t as easy as a simple wax or machine buff makes it look. Many people fall victim to thinking their paint is in pristine condition simply because it’s been recently detailed, only to wind up disappointed a few months later over their car’s newly visible scratches. It’s important to understand that not every scratch can be removed, but all scratches can be made less apparent to the human eye.

WHAT IS CLEAR COAT

Clear coat refers to the clear top layer of paint that is applied over a colored base coat, and is found on most modern cars. Clear coat increases the paint’s durability, gloss and resistance to harmful environmental effects such as UV rays; similar to a more permanent wax. Typically – and it varies by manufacturer – clear coats are 1.5 to 2 mils in depth (50 – 60 microns). To give you an idea of how thin this really is, 1 mil is 1/1,000th of an inch. As you polish, you’re taking off and removing microscopic amounts of this clear coat, and according to some manufacturers, there are limitations to the amount you should be removing. Here’s what the American companies say is the most you shouldever remove from your car’s clear coat:

  • Chrysler: .5 mils (12-13 microns)
  • Ford: .3 mils (7-8 microns)
  • GM: .5 mils (12-13 microns)

To make this concept easier, the basic idea here is that the more you remove, the less effective the clear coat is. That means every time you polish, you’re compromising the clear coat’s ability to protect the colored paint layer, rendering it more vulnerable to scratches, fading, and discoloration. To help combat this problem, some suggest preservation (filling) over correction (cutting) because it’s the best and only way to keep the clear coat as close to factory thickness as possible without repainting. Before removing or remedying a surface scratch, you must understand what type of scratch it is.

IDENTIFYING A SCRATCH

The basis of scratch science begins with depth. The depth of a scratch will determine whether it can be simply buffed out or has to be painfully repainted. If you were to examine a scratch as part of a cross section, you would notice the surface’s different layers: most commonly metal, primer, color, and clear coat (Figure 1). There are many different types of scratches and identifying their differences is the first step back to a lustrous finish.

  • 1A~1B ScratchesLevel 1A: A minor clear coat scratch is the easiest to take care of and is the most common type of scratch. These are left by almost anything coming into contact with an unprotected surface, even a dirty towel. These are harder to see simply because they’re not too deep, and are easily fixed without causing major harm to the clear coat (ie. hand polishing or light buffing).
  • Level 1B: The deeper side of clear coat scratches aren’t as easily taken care of, but can be effectively removed or reduced by proper machine polishing and rounding. 1B scratches are most commonly related to swirl marks and are caused by automatic car washes, poor technique, dirty applicators, or neglect. These are noticeably deeper than 1A scratches, but haven’t hit the paint.

Level 2 Scratch

  • Level 2: If you’ve noticed a scratch and you can’t see another color behind the pigment of your car, you can be sure you haven’t hit primer or metal. In this case, say the scratch has gone through the clear coat and into the paint itself; the color is still good, so touch up paint will not be necessary.  These are similar to clear coat scratches, other than the fact that you’ve actually taken a bit out of the paint. Since you’ve pierced the paint layer, level 2 scratches cannot be fully removed, but can be polished down to an almost unnoticeable level.
  • Level 3: If a scratch is into the primer, but not the metal, you’re still not going to be able to get it out, but you will be able to make it a lot less visible. At this depth you’ll usually see white or an off-white (even grey) color beneath the paint, signifying that you’re at the primer level. Although you shouldn’t have to worry about rusting at this depth, you should still take action. In this case, use touch up paint on the scratch as soon as possible.
  • Level 4: Level 4 ScratchIf the scratch has hit the metal, you’re going to have to repaint or use touch up paint.At this depth you’ll see a silver color when examining the scratch, and, if left untreated, the surface will slowlytransition to a rust.Neither waxes, glazes, or polishes will be able to fix a scratch that has punctured the metal, no matter what any “magic” product promises. If this situation has occurred, clean out the scratch immediately and grab some touch up paint as soon as 
    possible.

 

SCRATCH SOLUTIONS

Unfortunately, the world of automobile enthusiasts has deemed machine buffing the ultimate answer to any problem regarding paint. With no offense to the community, this is absolutely wrong if you’re interested in preserving the health, beauty, and longevity of your finish – think vintage cars with original paint. If you’re more of the 3-year lease type and your car has a predetermined lifespan, by all means polish away, but it’s important to realize that proper care can prevent the need to dig into your car’s clear coat in the first place. Also, if you’re set on machine buffing, remember that each time you take a machine to the surface, you will either be removing some clear coat or subjecting your paint to swirl marks.

Preservation begins with a mindset. Truly caring for your car’s paintwork is keeping it properly protected throughout the years, and this proves to be rewarding. As stated earlier, the less of clear coat you remove, the better job you’re doing at protecting the paint. The basis of preservation rests on filling rather than cutting, and keeping the largest amount of factory clear coat on the car as possible. This doesn’t mean that polishes and glazes are to be avoided, but rather the types of products need to be understood. Smoothing polishes and fine polishes are gentle on clear coats, and when used with a finishing glaze, help to fill and slightly round the edges of the scratch – making them less noticeable. Preservation successfully minimizes the appearance of all scratches, even level 4, by limiting the amount of light reflection within a scratch. The rougher and deeper a scratch is, the more light reflects inside the scratch, making it increasingly visible to the human eye (Figure 2). Although hand polishing will do just fine, preservation doesn’t necessarily mean no machines, but rather than a high speed or rotary model, an orbital buffer is preferred for this process.

Correction is the more aggressive polishing technique and is usually referred to as common practice within the detailing community. Also recognized as high speed buffing, cutting, machine polishing or fixing, correction utilizes more abrasive technology to remove clear coat scratches (1A). The amount of clear coat removed will vary depending on how deep the scratches are that you’re trying to get out, but always remember that the more you buff, less and less clear coat is left to protect the painted layer. By cutting, this process will successfully remove level 1A scratches and some 1B scratches from the paint. Although deeper scratches (level 2-4) can only be shortened and rounded, this process minimizes their visibility by allowing light a direct path of reflection. For paintwork correction processes, leveling compounds are used and utilized in stages – usually a more abrasive compound followed by a slightly less abrasive product, and finished with a glaze before waxing. Similarly to the preservation process, the finishing glaze is used to further smooth and fill any last imperfections after leveling compounds have been used – this helps to provide an even surface for wax application and minimizes the appearance of any deeper scratches that may not have been removed by the compound.

RECAP

For at-home and professional detailers alike, the importance of understanding and identifying (Level 1A, 1B, 2, 3, 4) surface scratches should never be understated. In the detailing world, paintwork correction and paintwork preservation are both techniques and mindsets that can be incorporated into any buffing procedure. For example, correction techniques may be used on some deeper areas, while preservation is used on the rest of the car. Combining the two comes with expertise, time and practice, but can prove rewarding at the end of the day. Becoming knowledgeable on the sciences behind clear coats, scratch depth, and polishing procedures will lead to smarter car care and, most importantly, a better looking car.

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  • Steve Miller

    Hi Dr, How do I get a light scratch out from my Veloster Matte paint. Only have had for 2 weeks and left next to 2 other good cars for 20 mins only to come back to find a scratch on rear. Please tell me how i would get this out. Thx

    • http://www.drbeasleys.com/ Dr. Beasley’s

      Hi Steve,

      I saw your email just as I was reading your comment. Because this is a growing question often asked by matte car owners, I thought I’d answer here to hopefully help out others with a similar concern.

      First off, congrats on your new Veloster! I’m happy you found us at Car Care Products Australia.

      As for the scratch in your matte paint, the short answer is purchasing matte touchup paint directly from Hyundai. Often times this can be found at a dealership, but for the Young Gun finish this may require special connection to the factory or even PPG (the paint manufacturer)… your dealer should be able to assist you.

      A longer explanation is required for why you cannot polish to remove scratches in matte paint, but I’ll simplify. In short, polishing matte paint wold smooth imperfections in the clear coat that make matte paint non-reflective, and begin to gradually increase the paint’s gloss. This irreversible damage to the factory matte finish, caused by polishing, can only be fixed by repainting the panel. This may sound a little harsh, but that doesn’t mean you can’t make your car’s scratch less visible…

      We have found some success making minor scratches less visible by using Matte Paint Cleanser followed by an application of Matte Paint Sealant. While this wont “fix” the scratch, it may make it less apparent depending on the depth of the scratch and how it was caused. We are constantly testing alternatives to this theory, so it’s in your best interest to stay tuned on our blog in the event that we announce a new product to solve this growing problem.

      In the meantime, please keep in touch and let me know if there’s anything I can help with. I’d love to see a photo or two of your car—especially the problem area—as this may help me better address your question.

      Best,

      James

      • Steve

        Big Thanks for getting back to me & the Info. I’ve ordered the Dr Beasley products so I’ll give it a go. I’m sure it will help to make it a little less visible. Cheers, Steve

  • http://www.facebook.com/SHERRIDOINGWAYBIGFRANKLIN Sherri Franklin

    Do scratches from bushes leave rust scratches in one day?

    • http://www.drbeasleys.com/ Dr. Beasley’s

      They should not. Could be some minor oxidation. Do you have a photograph?

  • Liz

    Hello! I am sure this thread is not active but i came across this when i was researching my problem, i have a glossy finish on my side mirror, however i bumped it against another car’s side mirror now there seem to be a coin sized portion that became matte, i have never experienced this before, so was wondering if that portion can be buffed out?

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  • Jay

    How can i touch up or fix a surface scratch on a plastic bumper its not deep.

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