The use of painter’s tape is an important part of the polishing process. I will explain all of the reasons why you would use tape or when you would choose to avoid using this kind of product.
Why do you tape a car?
The most common reason is to protect trim and weather-sealing from mechanical or cosmetic damage while polishing. Taping helps protect from staining of these areas from the polish residue (that can be challenging to remove) or lifting of these parts from the force of the polisher.
The other reason for using tape is to keep compound dust residue out of the cracks, hard to clean spaces between car panels. This polishing dust can get caught in the cracks or even stain the trim. It is not uncommon for me to tape a car in the first (more aggressive) polishing step and not tape in the second (nonstaining and nondusting) polishing step.
There is another reason why you tape a car; protecting sensitive painted areas.
There are areas of the car that may need to be protected from aggressive polishing or wet sanding. The edges of car panels are notoriously thinner, likely because of how paint is applied to a vehicle. Also over time paint will thin at raised body lines. The difference is very subtle but maybe enough for someone to mistakenly polish through the clear in these areas. It is not uncommon for me to find paint missing in these areas when I am inspecting an even newer car.
If you hear the term edgework, it is in reference to the act of precisely polishing small areas as well as concave and convex curves. The dialogue is often in reference to the challenge of doing a thorough job polishing a curvy car. But as you can see here it is also about safely polishing these surfaces.
You also want to use a high-quality painter’s tape, made for detailing. The use of the wrong tape or a cheap alternative can lead to some problems. These problems include very poor adhesion, extreme difficulty in removing the tape residue, and a higher likelihood of damage to the paint upon removal.
3M Precision Tape is one of my favorite tape products to use.
There are some situations when I will not use tape at all. The trim or weather sealing appears fragile or visibly damaged and the car is outside in extreme heat. Consequentially I will be concerned about melted tape residue. These are situations I will polish with extreme caution.