Does the single stage not hold up? Also is the clear hard to spray and how do you kep it from chipping as these new cars do my wife has a 93 mercury that looks bad from all the flaking of he clear and dont want it to happen to my truck....

 

Single stage isn't bad, but the life expectancy isn't that of a base clear. single stage will give the gloss when the color is sprayed. I recommend only spraying a solid color if using single stage. Not only are metallics and pearls a little harder to spray in a single stage, no buffing can be done to them without a clear on top. If a single stage metallic or pearl were wetsanded and buffed to get rid of some orange peel in the finish or dirt nibs, the metallic most likely would be ruined and blotchy. Don't let some auto manufacturers peeling clear scare you. A quality urethane clear if proper prep is done and mixed and applied correctly, and the tech sheet are followed, peeling shouldn't happen. Some things that could cause peeling to occur sooner are if the time window were exceded between base drying and applying the clear, wetsanding and buffing after cleared and cutting the clear to thin, or not applying enough coats of clear so there is not enough mil thickness (2-3 coats of clear should be good), spraying the base way to rough and dry so the clear doesn't bite into it. not sanding well enough when prepping, or sanding with way to fine of a grit. Possibly also if heavy coats were applied without enough time between and a fast reducer used, and solvents get trapped, but this more likely would cause the clear to solvent pop. The clear also has uv inhibitors in it which protect the color, meaning it is less likely to have the color fade. The base coat in a base clear system will dry fairly fast and isn't sprayed to achieve gloss and could be wetsanded in an hour or so say if you happened to get a small run or other boo boo, then more base sprayed on the area. Mistakes are easier to correct if using base clear. Spraying the clear wouldn't really be any different then spraying single stage, pretty much the same thing but there is no pigment in it. There will be a little more depth to a base clear paint job, cause of the clear coats on top of the color. These are some of the reasons mainly basecoat with a urethane clear is used today in most shops, other then places like maaco and production shops that scoot cars in and out the door. The single stage would cost less and not need the extra steps of spraying a clear to get gloss. Paint is going to chip is it is bombarded by rocks from a cement truck no matter if it is a base clear or single stage. It shouldn't chip real easy. Some brands may be a little more resistant to it though, and i can't really tell you one brand that would be better then another. Probably depends on how hard the clear cures when its finished crosslinking with the hardener.
Yeah. I am aware that enamel can be sprayed without a hardener, think I even said it earlier in this post, or maybe it was another one.
But I personally would never spray enamel without one, unless it was an enamel based basecoat possibly. Adding a hardener will make it more like a urethane and chemically crosslink to harden instead of relying on to air dry which could take dang near forever for it to truely harden through. Adding hardener will make the buffability better, give it better gloss, and durability.