The Stovebolt Site Forums The Shop Area Paint and Body Shop "Basic" questions

MartinSR, I just re-read your "Bondo" and "Rattle Can" basics and have a couple of questions.

1. You mentioned that cutting the original filler is typcially done with 36 or 40 grit. You stated that you had to learn to use 80 at one particular shop because that is all they had. Doesn't / wouldn't the very abrasive grits mar the adjacent surface and/or leave deep gouges in the paint? Or, should the skim coat cover the entire are that has been sanded/scuffed? Is the rougher grit merely to save time and form the material quicker?

I ask as I have recently attaced the hood of an old jeep that met the windshield one too many times and needed some attention. I pounded the dents out and sanded down the paint and old body filler to bare metal. Then, applied a coat of filler, sanded, and applied a second coat (I wasn't brave enough to try the one coat, sand, and skim technique you recommend) of filler, sanded, then the final skim and blocking. It appears to be very nice. Although, it now appears that my skim coat does not cover enough as you recommed an overage of about 3".

2. How do you handle complex body contours and shapes such as creases? Specifically, how do you form and fix an internal crease such as around a wheel well? I am not sure how to explain this in greater detail.

3. Should bondo be applied only to bare metal? Or is it OK to go over paint?

4. After the skim coat (remember, I'm not a professional) should I prime and block again to verify that the panel has been properly repaired prior going to final paint?

5. When applying paint with a spray can, should I apply more coats of primer in order to build the millage? You indicate that the standard thickness out of a can is about 0.5 mil. How many coats out of a can should I apply to obtain a satisfactory prime level?

1. Yes they would mare the surounding area. That is why you need to strip the paint and primer well away from where the filler work is. Leave at least five or six inches past where the filler will be bare metal. By the way, they don't always end like they begin. Very often, you find a need to strip more paint off. The skim coat should simply cover all of the previous coats.

2. Man, that is a tough one and would take an entire "Basics of Basics" to explain. In a nut shell you need to work a small area at a time. You sort of work many small area independly while looking at the big picture at all times.

3. Plastic filler should only go over bare metal or properly applied epoxy primer. Polyester putties can be applied over sanded paint with no ill effects.

4. I remember doing that when I first started. To tell you the truth, it adds a LOT of work. Better yet, just guide coat it with a very light mist of black lac paint in a rattle can. There are rattle cans labeled for Guide coat now a days, get one. You can see exactly what it will look like by blocking it (and hand sanding around those wheel wells and such). The guide coat will sand off very fast and leave the bondo. You will get a hang of it pretty fast. By the way, using masking tape to guide you on straight lines (for that matter I use it on curved lines too) is a big help while sanding.

5. Yes, more coats are needed. How many, only you can know. It really depends on how much surfacing your work needs.

I appreciate the help. I'll keep these in mind as I muddle along and teach myself the "basics" with a little help from those here...

Another question... Is glazing compound (the red stuff) susceptable to thinner? I finished some areas while still working on others, when I wiped the entire piece off with a rag wetted with thinner to remove the dust/dirt/etc... and it appeared to cut the finished glazed spots. Is this a no no?

My experience with glazing compound has not been good. Probably because I didn't get a good coat of sealer on it before top coating. It caused bubbling under the paint on the hood of my 49. Next time . . . not glazing compound, use a fast filling primer and then once everything is smooth, seal it good, then top coat it.