Block Sanding Your Mopar to Perfect Smoothness

Hyper-Polished Paint Requires a Perfectly Flat Surface—Here’s How to Get It

You’ve probably heard this a thousand times. Nonetheless, if you’ve been around the block more than a couple times, you already know the ultimate quality of any paint job is only as good as the bodywork underneath it.

But it’s not just about removing any obvious flaws. The reason a mirror reflects back a perfect image is because it’s completely flat. Any distortion in the mirror’s surface will equally distort the reflection. There are few places on a car that can be called flat, but with the optically polished paint that top-line shops like Muscle Car Restorations (MCR) produces, any deviation in the surface’s form will clearly be seen in whatever that surface is reflecting.

It’s much like how paintless dent repair works. A paintless dent repair technician uses the distorted reflection seen in the paint surface to guide the dent removal. When the reflection is perfect, the dent is gone. Of course, we’re not talking about dents here. The sort of panel distortions usually seen are typically much larger than a dent and much more subtle.

The solution to achieving flawless panels is to skim coat as needed and block-sand the entire car after it has been primed. No, Mopar never did this at the factory. The time and costs involved would have been totally prohibitive. Mopar also didn’t produce the level of gloss in its paint that is routinely achieved with the paint products of today.

And, of course, Mopar wasn’t working with nearly 50-year-old sheetmetal. Like it or not, even accident-free original panels aren’t going to be perfectly smooth anymore. New replacement panels today are mostly excellent, but all aftermarket and N.O.S. body panels have to be checked for minor imperfections, such as waves and leftover die marks from the manufacturing process.

These slight imperfections are not usually noticeable on a typical factory orange peel finish, but will become very noticeable on a high-end cut and buffed paint surface. Eliminating these factory defects and smoothing any patched or spliced areas requires advanced metal-finishing techniques, such as paintless dent repair and skim-coated body fillers.

It would be good to define what we mean by skim coating. First of all, it is not slathering on a bunch of filler to cover up bad metalwork. It is, rather, an ultra-thin pre-primer coat designed to provide a very smooth base for the show-quality paint that will follow. It’s the kind of basecoat that makes it possible to look down the side of a mirror like a polished panel and not see even the slightest hint of a wrinkle in the finish.

A good example of both of these situations is this 1970 ’Cuda. The sheetmetal was in much-better-than-average condition than most that MCR sees, and so much of the exterior metal was saved, with the major exceptions being the rear quarters, which are new Auto Metal Direct panels. Both the original metal and the new panels are proofed with block sanding and guidecoats to be certain they are ready for mirror-like finishes.

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