Blast Off

Plastic Media Blasting (PMB)

Bob Ryder Mar 24, 2005 0 Comment(s)

We have all heard the cliche "beauty is only skin deep." Well, that might be true in regards to prom queens and bikini contests, but not when relating to custom cars! The true beauty of a custom begins underneath its skin (paint). What makes a flawless paint surface is the attention given to the undersurface preparation. A car's body surface, whether steel, aluminum, or fiberglass, magnifies its imperfections after paint has been applied, buffed, and polished.

Whenever restoring or building a car, the most impressionable segment of its cool identity is its revived, straight, and smoothed body complexion magnified with layers of flawless paint and even more coats of clear. It's not just the color of the paint, but the entire presentation process that make the final coats of clear appear to be liquid glass.

Most custom projects are purchased with their body components (main body, doors, fenders, hood, and trunk) in somewhat rough condition. The present paint may show signs of oxidation, peeling, chipping, spider webbing, and/or a case of surface rust (unless you bought a real relic, which will most likely be all rust!). Depending on the age of the vehicle, it could be wearing numerous coats of paint, and most likely won't have the best of paint jobs, either. You could scuff the surface with an abrasive pad and invest in another cheap paint job, but some of the new paints perform questionably when applied directly over old paint. If you are going to put effort into building a respectable car, take the body down to the bare-metal surface and start fresh.

The most practical means of paint removal and original bare surface exposure is plastic media blasting (PMB). This is the process of rapid, economical, and environmentally safe removal of coatings and paint from almost any surface without introducing toxic acid dipping, chemical strippers, sandblasting, or hand/mechanical abrasive methods.

Plastic media blasting is similar to sandblasting, but instead of using hard, abrasive silica sand, much softer reusable matter with plastic particles is used at a lower pressure (14-40 psi compared to 60-100 psi). The heavier pressure can cause material surface damage, heat warping, pitting, and stretching. At these lower air pressures, the plastic media is able to remove the coatings or paint without causing damage to the underlying surface, including materials like aluminum, fiberglass, and even plastics. There are five major types of media used: polyester, urea, melamine, acrylic, and clear-cut.

When working with a timeless vehicle, it's always best to remove the decades of paint, oxidation, and surface rust. Getting down to the original surface will make things go a lot smoother in more ways than one--plus, it may tell you a few things about your car you never suspected (like well-hidden cancer rust or excess body filler). Surface preparation is the most important step to achieving a super high-quality paint job. To experience the pigment removal sequence, we hooked up with Darrell Holstad, owner of Media Resurfacing Systems in Huntington Beach, California. Holstad has been involved in custom automotive "expression" and media blasting for some 30 years now, and knows a thing or two about proper preparation. We will be following right behind him as he removes the original paint from a "low-fin/cat-eye" '59 Chevy Bel Air.

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This is how we found project "Cat Eyes," complete with all the hard-to-find stainless body moldings and trim intact.

The emblems, moldings, trim, turn indicators, headlights/buckets, bezels, and fender "rockets" had to be removed (and labeled!) before the '59 was trailered over to MRS.

Plastic media is available in five different types and many different sizes to meet the requirements of specific body finishes and substrates. The individual particles are irregular in configuration with granular surfaces that incorporate sharp, angular edges. During use, an effective cutting, shearing, and lifting action results.

Before activating the PMB system, Darrell inspects all 16 massive air filters...

...in the gigantic Torit down-flow air-filtration container.

The windshield and rear window were carefully removed before we rolled the '59 into the spray booth. Due to the fact that the two rear side windows don't retract all the way into the quarter-panel, Darrell covered them with a thick urethane sheet to eliminate any etching that might be caused by the blasting.

Darrel slips into his protective OSHA-approved blasting suit with a fresh-air-circulated helmet. Steel-toe boots are worn as a precautionary measure, as well.

With the air pressure set at 30 psi, Darrell begins the media blasting procedure starting at the rear.

After media blasting the paint away, we discovered some minor bodywork done with a dent puller and some minimal body filler (we got off easy--way worse has been discovered "after the blast!").

Moving to the front, Darrell begins blasting the hood starting from the outside and working his way toward the center, checking the surface temperature with his bare hand as he goes.

After the hood was completely blasted, the interior attracted the attention of the media blasting nozzle!

The original paint was also removed from the firewall. Eventually, the main body and firewall will be the same color--Viper Red!

Finally, the two front fenders were blasted to bare metal. After blasting is complete, it's wise to coat all exposed metal with a good etching primer. If the body is to sit for any extended length of time, a good sealer is recommended, as well, to prevent any further deterioration of the surface. While bare metal can actually sit exposed and not immediately begin to rust, chances are the car will be moved, and the acid from your very hands will initiate the rusting process faster than you think!

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