The Art of Sanding Primer

i just watched on trucks where they wet sanded primer. they did use 400 grit, but used a spray bottle and not a water hose. all you need is enough to get the area alittle wet before you start on it. i have yet to do it, but it looked pretty easy and very time consuming...should get you away from the wife for a few hours...0=)

 

Way to go dan

 

cool beans. i am moving to florida in a couple of months maybe i can jot down and get some painting tips..0=)

 

I agree, wet sanding is the way to get the surface smoother than a baby's butt. A couple of observations:

1) I use something to back up the sandpaper. A block of wood or a hard sponge for flat surfaces and outside curves, a piece of radiator hose or heater hose for inside curves, etc. Using just my fingers generally gives an uneven surface result.

2) When wet sanding, I use silicon carbide sandpaper (wet or dry paper, available at your flaps or any automotive paint store) It will not come apart when wet.

3) 400 grit (U.S.) is probably the coarsest grit I would use for wet sanding. The larger the number, the finer the grit. Most places are now going to the European, or "P" designation. Up to 180 grit the "P" grades and the U.S. grades are the same. (e.g. 100 grti is the same coarseness as P100) After that, the P grades become coarser than the U.S. grades. For example, to get 400 grit U.S. in a "P" grade, you would have to get P800.

4) Be very careful when sanding sharp ridges. Its very east to cut through the primer to the metal.

Just my $.02 worth.

tommy b

 

8)

 

Are you done yet? :toetap: :toetap: :toetap:

 

Dan, tell us what equipment you are using. Type of gun, paint etc.
Thanks.

 

Looks like you are done with the sanding, but I will post any way. I always end up doing a lot of paint and body work here and there. For the most part on primer, I always use 400 wet using a spray bottle to keep the paper clean and always by hand on the final primer coat. Most times, I take a paint stick and break it to around 8" long to wrap the sandpaper around. Also, try to sand at an angle on the larger surfaces instead of any straight lines and never go in circles with it. Just my .02 from what I have learned from some body men around here.

 

A good way to find low areas in your primer is to fog on a light coat of rattle can lacquer primer of a contrasting color If you have a light colored primer and you use black lacquer for the "guide coat" you will have black spots all over. When you wet sand with a block or paint stick, the first thing to go will be the spots. If you come across a low area, the spots will remain until you sand down to them. The trick is to get rid of all the black spots without sanding through to the metal in adjacent areas. Otherwise, you have to apply another coat of primer to the area, guide coat it again, and resand. In the attached pic you can see my Ford with the guide coat on, ready to be sanded. Hope this helps.

tommy b

 

Nice old Ford. I usually put a little dish washing soap in my water spray bottle. It helps reduce the clogging of the sand paper and, in the finer grits, keeps the paper from sticking to the surface.

 

I was going to mention the guide coat, but I couldn't figure out a good way to explain it without causing someone to completely paint the whole vehicle. The pic you have should say it all on how to spray the guide coat.