Painting cars has changed since the early days of automotive production. In the ’20s paint was about one step away from varnish and was applied with a brush or flooded as it was on Model Ts (Ford applied paint at the top of the body with something akin to a wide sprinkler head, it literally ran down the sides like one continuous run and was captured at the bottom in trays to be reused). It wasn’t until 1924 that Oakland automobiles became the first to be painted with a spray gun, thanks to a dentist named Dr. Allen DeVilbiss. In 1888 he created an atomizer to spray medicine into patients’ throats. The doctor’s son, Thomas, expanded on the idea and created what is acknowledged as the first spray gun for paint.
During the ’30s, paints improved and alkyd enamel and nitrocellulose lacquer were commonly used. Enamel was tough, but it oxidized rapidly and became dull. Lacquer had more gloss but was susceptible to chipping. In some cases both finishes could be found on the same car—enamel covered the fenders and frame for durability and lacquer was on the bodies for greater gloss. Through the ’50s nitrocellulose lacquers remained a favorite of custom painters and continued to be used on some passenger cars until acrylic lacquers were introduced. Another improvement in automotive paints came in the early ’60s with the introduction of durable acrylic enamels.
While acrylic enamel and acrylic lacquer were popular, there were significant differences between them. Enamel was tougher, but was far more difficult to apply. It was not possible to color-sand and polish enamel, so what came out of the paint booth was what you lived with. Lacquer was certainly easier to work with but it required polishing, which took time but the results were worth the effort. As a result of these characteristics most repair shops chose enamel, while custom painters continued to use lacquer.
An interesting development came with the advent of hardeners for acrylic enamel. Appearing to have the best attributes of both lacquer and enamel, many painters believe that if a little hardener was good, a bunch would be great. The end result was often crazing and paint that came off in chunks.
Another gigantic improvement in the appearance and durability of automotive paints came in the late ’70s with the introduction of two-stage, or basecoat/clearcoat finishes. At first expense was an issue, but it didn’t take long for automobile manufacturers and repair shops to recognize the benefits of these better-looking, higher gloss, more durable finishes.
While paints continued to improve they also became more toxic. Better personal protection gear was needed, improved booths and the federal government got more involved because of something called Volatile Organic Compounds (VOC). VOCs are unstable, carbon-containing compounds that are released when solvent-based paints are sprayed and as they dry. When VOCs enter the air, they react with other elements to produce ozone, which causes air pollution and a host of health issues. One method of reducing VOCs was with the introduction of High Volume Low Pressure, or an HVLP spray gun. More material makes it to the surface and less is lost to the atmosphere during application. Of course the real change came with how materials are formulated.
VOC emissions are established by pounds per gallon of material. And while there are federal regulations that apply, VOC limits vary from state to state. California’s South Coast Air Management District has strict guidelines and some of the products available to the rest of the country are not sold there.
When deciding what paint products to use, the number of choices can be confusing. To make sense of it all we turned to the pros at PPG.
PPG has a long history in the paint business, going back 1928 when it purchased Ditzler Inc.—the leading OEM supplier for automobiles at the time. Today, PPG offers products for industrial applications, fleet owners, body shops, as well as specialty and custom painters. PPG’s brands include the Global Refinish System, Deltron, Nexa Autocolor 2K, Delfleet Evolution, Envirobase High Performance, the Vibrance Collection, and Commercial Performance Coatings.
To produce a quality paintjob a variety of products are required. Here is a look at the common materials used:
The function of any primer is to provide a surface for paint to adhere to. Primers by nature are thin and do little to fill imperfections. There is no advantage to heavy coats of primer; in fact it should be avoided.
These products are a foundation for the paint, plus they fill imperfections. Multiple coats of primer-surfacer will build a thick film quickly and allow for block sanding to get rid of surface irregularities and provide a superstraight base for the topcoat. Always keep this in mind—if the car is not straight in primer, it won’t get any better with paint. That’s the reason bodies are often block-sanded several times.
Contemporary primer-surfacers, such as those available from PPG, are catalyzed, which eliminates shrinkage and the sand scratches that used to result from the solvent evaporating from lacquer-based products. Additionally, primer-surfacers provide excellent corrosion resistance and a chip-resistance base for color coats.
These products are intended to keep the solvents in the topcoat materials from penetrating what’s underneath, as well as preventing undercoats from bleeding through. If you’ve ever shot lacquer over enamel and watched the surface wrinkle like a prune, you understand the need for a sealer.
PPG’s epoxy sealers are unique in that they serve a dual function, acting as both a primer and a sealer, in some instances they will also take one step out of the finishing procedure.
Again, primer-sealers are not designed to fill imperfections, so heavy, multiple coats are a waste of material. One light coat is all that’s necessary.