By Carl Wilson
Note: this story is Part 1 of a six-part series.
Few things are more frustrating to a painter, body man and shop – or detrimental to cycle time and margins – than a redo, a comeback or an OMT (one more time). Whatever you call it, efficiency and profitability suffer when we make mistakes. Yet we all make mistakes because we’re all imperfect humans. And while no one “bats a thousand,” we can often pitch “no hitters.”
There is nothing faster and more profitable than accuracy – doing the job one time. In fact, there are few things more unprofitable than doing it a second time. I’m certain we can all agree that doing it a third time is one of them.
In this article, let’s consider those pinholes that “show up” after the painting is done and the sand scratches that weren’t there before. Where did they come from?
Pinholes are caused by air entrapment within the plastic body filler and are exposed during the sanding operation of the filler by the body man. Yes, we painters all know that pinholes come from the body man. And there are plenty of resources available to the body man that deal with the cause and prevention of pinholes. Our purpose here is dealing with them once we have the job in the paint shop.
Sand scratches are too coarse a scratch pattern in the filler, or an improperly feathered paint edge surrounding a repair that has been primed over. The primer-surfacer appears to initially fill the scratch, but the problem is that the primer-filled scratch behaves differently than the surrounding body filler and eventually telegraphs its presence to the surface. Think of it like an expansion joint in concrete.
Sand scratch issues must ultimately be dealt with by the body man to ensure they aren’t ongoing problems. The grits of sandpaper (40, 80, 120, 180, 220, etc.) must be worked through by the body man, with a final grit scratch of 220 or 240. So, 220 or 240, which is it? It’s 220 if the scratch pattern is left by a random orbital; 240 if the scratch pattern is left by straight line hand sanding. A random orbital scratch is always less aggressive than a straight line scratch of the same grit.