I am ready to shoot black PPG basecoat on my 69 shark. If it doesn't layout perfectly flat, can it be sanded be fore the clear? If so what techinique is recomended - wet sand with 600? Thanks again for any help you can provide.

 

Several years ago, my boys and I shot base coat/clear and I sanded before the clear. Make sure you have enough base to sand. I used wet 600 and 1200 grit. Sanded to where it had a shine (I buffed). Results were great. Remember, depending on the serface, use a long flat sanding block. Don't gouge if there is a run. If you screw yp the basecoat, just put more on before the clear.

p.s. You can sand the clear too using wet 1200 and then buff.

Good luck.

 

Also if there are any flakes in it you don't want to sand it!

Otherwise go fer it

 

YOUR NOT SUPPOSE TO SAND BASE COAT UNLESS YOUR GOING TO RECOAT THE BASE.
OTHER WISE YOU WILL SEE SCRATCHES IN THE CLEAR COAT YOU WILL NOT GET OUT BY RUBBING
NTQ

 

 

No, base coat is not supposed to be sanded without respraying. If you get a run or a sag you have to sand and then respray the base.

 

I think you have a time limit to spray the clear anyway, I recall its 24 hrs, but someone will probably correct me on this. Just spoke with a guy who used SINGLE STAGE, and he sanded it, then another single stage coat, sanded that, then clearcoated. He said it came out like a mirror. I didnt know you could clearcoat single stage....?????
Rob

 

Clearing a single stage really gives a deep look. I mix ppg concept at home, and I believe the tech sheets say it can be cleared, so it's nothing to be skeptical of.

 

The reason you don't sand the basecoat is because most manufacturers use a parifin (wax) additive. Sanding it smears it and the clear won't adhere to it properly. For an experiment, spray some on a spare panel, sand and see for yourself. Of course, if includes metal flake, it will ruin the lay-out of the metalic particles and you will see scratches in the clear. If you get a run in the base, or insect, etc. you can lightly wetsand that area, then spray a little base over it prior to clearing. I've gotten away with doing that.

That being said, some manufacturers don't use parafin in the basecoat. I believe it's Sikkens (at least they once didn't). So, at the time my buddy that used Sikkens would make a big deal of wetsanding the clear. Check with the PPG guys to make sure what they say.

Anyway, a little texture in the basecoat is normal and you won't see it once the clear is on. Initially you might see texture after you spray on the base, but let it sit for 15-20 minutes and it should flatten out after the solvents have flashed off. If you're getting too much texture in the base, you should double check your spray gun (nozzle/cap, technique, or mixing ratio). Once completed you can sand/buff the clear for a nice, flat show-car finish.

Mark G

 

So is there any reason NOT to clearcoat single stage, other than additional cost and time?? After ANY sanding, even 2000 grit, should the SS be shot again prior to CC?

Thanks.

 

I personally would not clearcoat a single stage w/o first talking to the mfgr paint rep. They used to caution against clearcoating single-stage paints, and at one time Martin Senour (Sherwin Williams) had an additive (basically parafin) one would add to enamel prior to spraying clearcoat over it. The issue was delamination of the clear. I heard some reasons why from painters but never really asked a paint rep. I know guys that have done it, but usually as low-dollar repairs on customer's cars, and who really knows how long it lasted?

I would encourage you to talk to the paint rep first. The cost of paint is so cheap compared to the effort and preparation hours you put into your car. Ultimately, I can't think of a good reason why anybody would go to all the effort and cost to prep and paint a corvette and save a few bucks at the end using single-stage enamel or cut corners instead of a decent B/C urethane system.

 

Mark,
I totally agree, but after speaking with a guy (in a bar) who had cleared over SS, and said the result was really gorgeous, I just thought I'd ask the question. I'm definitely not trying to save $$ or cut any corners! This has been a good discussion. I plan (when its time) to do PPG BC/CC.
Rob

 

I also agree... I had to sand a few paint drops out, (drops that poured out of the top of the gun) The base has to be perfect! If you look close at that sanded area, you can see a difference which will show a problem (it looks like it is scratched)... What I did, sand the spot or runs, spot with base and then base the whole car again. Came out great! Muddy

 

A trick that I read about and just recently used on my car is on the very last basecoat, instead of thinning 1:1 with thinner, thin the basecoat 1 part to 2 parts thinner. This will flatten out the bottom coats if they are rough and even out the metalic.

It worked great for me My basecoat came out with the texture of paper.

I did have some debris, a hair or two on a panel. I wet sanded the basecoat with 1500 and re-sprayed the last coat. You will have to re-spray after sanding since sanding disturbes the metallic layout.

 

spray that basecoat dry as hell and you should be ok and wont need to sand it.

 

Spraying the base too dry will make more dry overspray and more orange peel. On a metallic, spraying it too dry can make the flakes stand up.