How does buffing a scratch out on a car work?
In: Engineering
Cars are painted in 3 primary layers. From bottom to top they are:
1. **Paint Primer** – this layer is a specific blend of paint that adheres well to the bare metal of the vehicle as well as other paint. It also better protects the vehicle than regular paint alone. It doesn’t color very well and is layed on pretty thick. It is usually a flat matte, gray color.
2. **Cosmetic/Colored paint** – this is the actual layer that you see. It’s comes in all different shades and styles. It’s actually the thinnest coat on the vehicle.
3. **Clear Coat** – this is not really paint at all, but actually more like a resin. It’s applied about 2-3 times as thick as the cosmetic coat, and is see-through (hence the name ‘clear coat’).
After the clear coat is dry it is buffed – this smooths out any imperfections. Essentially, buffing melts the clear coat in a localized area and smooths it out, so when it cools it is more evenly distributed and gives a nice shine finish to the car.
Since the clear coat is so thick, most scratches will not penetrate all the way through it (i.e. down to the cosmetic layer). You can buff the area with the scratch and it will once again melt/smooth out the clear coat in that area.
If a scratch goes all the way down to the cosmetic/primer layer, however, you’ll likely have to have that area ‘touched up’ with new paint and clear coat. Buffing alone won’t do anything.
Buffing essentially sands the surface of the paint with progressively finer and finer grits. What starts as a hazy, scratchy mess becomes finer and finer scratches until those scratches are smaller than can be resolved by the human eye.
At that point it looks smooth.
Imagine if there was a dich in your lawn, and instead of filling it in you dug the rest of the lawn down so it was as low as the dich.
Buffing is basically that, but on a much smaller scale.
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