Sanding Basics - Papers
Sanding is extremely important for obtaining a blemish-free finish. Here are some basic facts about the types of sand paper and how to use them.
The first step is shaping the body filler to the correct shape and contour. The second step is to make all surfaces true and to get rid of all deep gouges left after the first step. After that, the body worker uses medium then fine grade of sand paper to remove all of the marks left by the previous operations.
If you have access to sanding equipment used in professional body shops, it is important not to cause deep scratches or surface ripples by pressing too hard.
You can sand by with using wet-sanding techniques or dry sanding. Tip: put a little soap in the bucket you use for wet sanding. This will prevent the water from running off of the panel you are working on and helps slow down clogging up of the sand paper. Use plenty of clean water. Remember to be careful not to pick up any grit from the bucket of water from which you are working and wash the sand paper in clean water should you accidentally drop it on the floor. Also, change water between grades of sand paper.
Dry sanding involves using "open coat" sand paper, some of which incorporate a dry powder lubricant. Open coat sand paper produces a finer surface than wet sand paper.
Open coat sanding is a better procedure than wet sanding for a number of reasons. The water can get behind masked-off areas only to come out when you use compressed air. The water can also cause humidity blisters and rust if the surface is not allowed to dry thoroughly. And using water takes extra time simply because you have to wait for it to dry.
Remember to wash away all traces of sanding from the body surface after you are done, sponging it with clean water. The stearate lubricating powder in some open coat papers if left on, can prevent the color coats from adhering. Wet sanding can leave a paint residue; and if you allow it to dry on the body part, it forms an alkaline remainder that is difficult to remove.