I fixed a couple of dents in my truck. The dent repair went well but i had some problems with painting the repairs. First step was two to three coats of high build Duplicolor primer, then sanded with 400 grit. I then used a color code correct paint that a body supply store mixed and put in a rattle can. It was Sherman Williams paint. The base coat went on smooth and shiny. I didn't sand the base coat prior to clearing as all the info i read was split on whether it was necessary or not. I then sprayed on a Duplicoolor clear coat. That's when my troubles started. The clear turned a very dull matte. I let it dry about 36 hrs then wet sanded with 1500 and 2000 grit followed by buffing using a 7 inch polishing machine with a wool pad. The clear never did shine and continued polishing only resulted in removing the clear coat.
I guess I'll have to sand the area down and respray the base and clear, but how do I avoid this problem with the clear happening again.
Recommendations for a spray can clear?
Also how do you prevent/remove/blend overstay?
I'm hoping the smart members of classic olds can help me. It seems the more I Google the more confussed I get!

 

You have to understand, spray can paint is almost always lower quality, and to be able to go into the can, and spray out that tiny nozzle, very thin. Most auto touch up paints are also lacquer based. This doesn't mean poor quality, but lacquer is reduced a LOT, and is very thin. It can be 2 to 3 parts thinner to one part paint. All that thinner evaporates as it dries. It is also prone to blushing, or clouding up when it's humid out.
Most likely, your clear is too thin a film, and even spraying lacquer with a gun, you need 5-10 coats of it, let it dry for a week, then carefully sand and buff to get a good shine. If it did blush, buffing won't help, though. You must sand it, and spray more when it's dry out.

 

Thanks for the info Chopolds. That could have been the problem alright as it was fairly humid. Also my garage was only about 60*, was too cool?

 

Unlike modern catalyzed materials, lacquer is not as fussy about temperature. Catalyzed paints won't fully cure if under 60-65*. Lacquer is air dry, so as long as there's some air flow, and the temps aren't too low, it will dry. The problem occurs, when doing your coats. Lacquer needs to flash off enough thinner between coats to dry properly. If it's cold, wait time between coats would have to be pretty long. If you put coats on too quickly, in any temperature, you will get "solvent pop". Where the solvents migrate together, when trapped under the top coat, and eventually rise to the surface, even days later, and leave bubbles, or pop and leave holes. "Back in the day" they used to sell proper lacquer thinners formulated for different temperature ranges, i.e., slow dry for higher temps, fast evap. for low temps. You can't do this with spray cans, or today's pre-mixed lacquers that are sold.

 

When I spray to the edge of what is sanded I always end up with overspray on the original paint. How do I fix this?

 

I'm not a fan, or user of spray can stuff much, so I'm not an expert. With "real" paint you can over reduce it to cut down on overspray at the edges, or do a 'blend' with a little bit of clear and lots of reducer. You have a lot more control over your spray pattern and laydown with real spray guns, too. Even just a slow dry reducer to melt the overspray onto the surface, will eliminate that dry overspray. Maybe there is a blending agent in spray cans? You'd have to be SURE it will work with your paint system, though.

 

I wish I had a spray gun, but I don't and for this small job I thought rattle cans would suffice. I have a 2K clear and an aaerosol blending solvent both by Spray Max so hopefully that does the trick. So if I spray the new clear on to he unsanded original and use the blending solvent should that work?

 

No. The proper way is to sand the area where the blending is to take place. Use a very fine grit, something that will be taken out by buffing, later. 1000 grit or finer. Be sure to go beyond where you intend to blend. The new clear will not stick to unsanded clear.
At that point, spray your color, feathering it out in case of slight mismatch. Then cover your color with clear. 2-3 coats (with a spray gun, probably need a few more with cans) Now the blending starts. Put a light coat of blender at the edge of the color/clear boundary. Don't wait too long, put another coat of clear on, this time extending an inch or so onto the blend area. Hit the blend area with another light coat of blender. Let dry a bit, and do the same, going a bit farther out. Maybe even a third time. Always soften the "new" area to get clear with blender, and after clearcoating, be sure to put more blender on to melt it it. You only have to do this on the area that is getting it's first coat of clear. But be sure to extend the blender a bit onto the last edge, and beyond where you cleared, to melt it all together.
Don't put too much blender on at any point, it can melt and drip the clear, remelt the basecoat and cause metallic float, or even attack the paint edges and wrinkle them.

 

Thanks Chop, that's basically what I did although with rattle cans it is hard to not get the clear beyond the sanded area. The blender worked great on the clear, except where I over applied it an caused a run. Very impressed with that Spray Max 2k clear coat. A beautiful shiny, hard finish and hides sanding marks well.