Paint Stripping Refined

Paint jobs have become one of the largest expenses of restoring a car. A quality total repaint, including jambs and all the areas necessary for a color change, starts at $5,000—and goes up from there. If you're making that kind of investment, you want the new paint to last for at least 10 years, if not more. To ensure a lasting paint job you need to strip the vehicle down to bare metal and apply the best paint/primer sealers available. The downfall of most paint jobs is the build-up of old paint, primer and body filler that is painted over. These old materials deteriorate with age and are sometimes incompatible with new paint materials. Deep cracks called "checking" and shrinkage around repaired areas are common problems.

Usual Methods
There are four basic ways to strip paint off your vehicle in preparation for a total repaint. The most obvious is to totally sand all of the paint off with dual-action sander with some fairly coarse sandpaper. Sanding is a time-consuming job that doesn't do a very good job of getting into the tight creases and crevices, so a lot of hand work is involved to get all of the paint off, not to mention the mess from the dust. The next two methods can be classified as chemical stripping. The most common process is to apply a strong aircraft-type liquid paint stripper with a paintbrush, let it soak, then scrape off with a putty knife. Anyone who's stripped a car this way knows why body shops charge upwards of $1,500 for the service. It's labor intensive, and makes quite a mess. Plan on using several applications of paint stripper and removing the final paint residue with coarse steel wool and rubber gloves. The second method of chemical stripping involves dipping the entire body into a commercial, chemical stripping tank. The downside to this method is that the vehicle must be totally disassembled to a bare body shell. A common problem with both forms of chemical stripping is that it is very difficult to get all of the chemicals out of the folded body seams. These chemicals have a way of surfacing after the paint job, causing blisters and peeling.

Fantastic Plastic
That brings us to plastic media blasting—not to be confused with sand blasting. Sand- or abrasive-blasting, while ideal for some automotive components, can literally ruin sheet metal. Due to the pressure and heat generated by most sand-blasting procedures, a car body can be warped beyond repair. Plastic media blasting will not warp sheetmetal because of the low air pressures used for blasting plastic; and, because of it's non-abrasive nature, will not remove any material from the steel sheetmetal—although it will erode the softer lead filler used to fill factory sheetmetal seams. Plastic media blasting will remove paint, undercoating, old plastic body filler and literally blow holes through heavily rusted panels. But that's a good thing because you need to clean out the rusted areas before you repair them, and all old plastic body filler material should be replaced with new filler before the repaint.

Gentle Blast
Why does plastic media blasting work so well? Scott at Speed Strip Deburring in Los Angeles, California explains it this way. "We use a catalyzed plastic that is ground up to the exact granular size our equipment requires. In the grinding process, these plastic granules become faceted similar to the shape of a Stealth F117 fighter. This plastic media has about 1/3 the density of sand and is non-abrasive to most metals and hard surfaces. In fact, we even blast Corvette fiberglass bodies. About the only body material that we don't blast is 0-tempered aluminum found on some exotic sports cars. Tempered aluminum components such as those made out of T6 clean up very well with plastic media." Scott is quick to point out that you won't find plastic media blasting facilities around every corner because it takes a special blasting booth and an extremely large air supply. However, these services are available in large cities or areas that have a large aircraft industrial base. Expect to pay $650 to strip the outside of an average-size car and $1,000 or more if you want the underside blasted as well. After blasting, the parts are ready for bodywork or primer. The time and effort you save more than offsets the costs of blasting with plastic media.