WHAT IS A SCRATCH?
In order to understand scratch repair, we must first understand the nature of a scratch itself. Obviously scratches come in all sorts of shapes and sizes, but at an elementary level, a scratch is nothing more than some type of abrasion in the paint. Scratches basically come in two categories: Surface Scratches, and Deep Scratches.
To help you visualize this I have attached a simple graph below:
You can see here that not all scratches are created equal, and because of that, automobile paint scratch repair is a very loaded subject. In an effort to keep things simple I am only going to touch on the most basic points, and answer some commonly asked questions.
Scratches that are relatively easy to fix are called, surface scratches. This means that the scratches are above the clear coat, and therefore can be removed pretty easily through some regular polishing. In order to see if the specific scratch or scratches on your own vehicle are above or below the clear coat, you need to preform the "fingernail test." This is exactly what it sounds like, gently drag your fingernail against the grain of the scratch, and see if your nail catches on it. If so, that scratch, or at least that specific part of that scratch is below the clear coat and will need to be removed through wet sanding and polishing (to learn more about wet sanding, visit the wet sanding part of the information page).
Repairing deep scratches is a little more complicated than surface scratches. In order to fix a deep scratch it will require wet sanding at some level, and then a polish to follow. This is because the scratch itself is through the clear coat, therefore in order to fix it, the clear coat must be sanded down to the level of the scratches depth, which will remove the scratch, then polish will bring that part of the paint back to a glossy finish. When determining if a scratch is considered surface or deep, it is important to preform the fingernail test on all parts of the scratch because some parts of a single scratch may be shallower than other parts. In other words, the beginning of a scratch may be classified as a surface scratch (which can be polished out & won't wet sanding) because you don't catch a nail. The middle of the scratch may be where your fingernail catches and that's where you'd have a deep scratch (which will require wet sanding) As a rule, most scratches tend to get deeper in the middle rather than the beginning or end of the scratch.
CAR PAINT SCRATCH REPAIR
Scratch repair is never as simple as we would like it to be. It is important to understand that not all scratches can be fixed 100%. For example, if a scratch has cut through the clear coat and into the paint, no amount of wet sanding or polishing will bring it to perfection, however if it cannot be fixed, it can be improved. This is something I tell all of my customers before I ever start the scratch repair process. I cannot promise it will be restored to perfection, but I can promise that from normal viewing distances, you'll never be able to tell a scratch was ever there. It's also important to understand that a vehicle only has so much clear coat. At some level, most customers will have to accept that there will be a certain amount of scratching or defects on their vehicle if it's a daily driver. As a rule, I will only wet sand a certain amount of the clear coat before I stop, because the clear coat protects the paint from the sun, I do not want to take a large amount of it off.
RETAIL SCRATCH REMOVAL PRODUCTS
As a rule, most of you will be very underwhelmed with the results you'll get from some of the retail scratch removal products. A retail scratch removal product is reserved for the most minor of minor scratches that exist. They normally do not contain any abrasives, and therefore are not even considered "true" polishing products. They simply contain chemical cleaners in them that can remove extremely, extremely light surface scratches. Most of you are dealing with scratches that are too deep to even be affected by the retail products. I don't dislike the retail products, and they have there place, but just understand that unless the scratch you have in mind in extremely minor, you may be disappointed. Here are some examples of the products I am talking about: