After painting an automobile with a pigmented undercoat, you can give the finished product added depth with one or more coats of clear-coat, an un-pigmented lacquer, enamel or urethane. Beyond improving appearance, lacquer and enamel clear-coats protect the underlying pigmented paint layers. You can describe the chemical differences between them in a few sentences. Describing the social differences in their use, and how one, although technically superior, never completely replaced the other provides a fascinating glimpse into California car culture, where clear-coats began.
The Heyday of the Kustom Kar
The heyday of custom cars (frequently spelt Kustom Kars by enthusiasts), extended from the early fifties through the seventies. "Stock" American cars ("Detroit iron") morphed into gleaming low-slung objects of young American male desire. "Clear coat," the transparent outer layers of a custom paint job, almost always lacquer, did protect the signature metallic gleam of the underlying paint and also provided visual depth, but, equally important, it provided what sociologists call a "signifier:" an apparently inconsequential, even meaningless "something" that powerfully stands for something else. In this case having a multilayer lacquer clear-coated finish on your automobile signified you belonged to the cult of the Kalifornia Kustom Kar.
Customising cars occurred everywhere, but the most revered practitioners all came from California or migrated there to become (briefly) immortal: George Barris, who possibly originated the Kustom spelling, Carl Casper, Ed (Big Daddy) Roth, Tommy (the Greek) Hrones and Norm Grabowski, who created the car Kookie drove on "77 Sunset Strip." For all these customising pioneers, the intensive labour required to spray the many layers required for a lacquer paint job became an important aspect of value: Hot Rod Magazine's monthly featured car article almost always described the painting process and commented approvingly when the builder used as many as 50 layers of clear-coat, each layer hand sanded with increasingly fine sandpapers. In this sense, lacquer provided the perfect medium. The more layers you added, the richer and deeper the finish became, and the many hours of painting and sanding this required demonstrated how much you cared about your car.
The Kandy-Kolored Tangerine-Flake Streamline Baby
Tom Wolfe's 1963 pop-culture narrative, "The Kandy-Kolored Tangerine-Flake Streamline Baby," popularised the phrase about a decade after the early customizers popularised the painting technique. They mixed almost microscopically small metal chips, often aluminium anodised (an electrolytic process) a bright orange ("tangerine flake") or red ("candy-apple flake"), into nitrocellulose lacquer paint. These fast-drying organic lacquers came from various natural materials, like cotton, with cellular structures. Since the anodised flakes oxidised easily, over-coating the metallic paint with more layers of protective clear-coat provided an attractive solution that soon became a near-cult.
Automotive paint had never looked like this before. When sunlight bounced off the metal flakes the finish nearly danced. Unfortunately, "a lacquer paint job was somewhat self-destructing. That is, after a few years it would get so hard that it would begin to crack and chip." The more layers you added the more beautiful and fragile it became. Many of Barris' most flamboyant creations really did become museum pieces--the paint became so brittle you couldn't drive the cars without cracking and crazing the finish. Customizers began looking for a durable substitute. They never found one they accepted. Authentic restorations today still require lacquer, and, ideally, the natural nitrocellulose lacquer rather than the synthetic acrylic lacquer substitute.
In most commercial automotive applications (as distinguished from custom car applications), enamels gradually replaced lacquers. Since pigmented enamels also oxidise unless protected, clear-coat enamels then replaced organic nitrocellose clear-coat lacquers. Automotive enamels come from alkyd resins: synthetic compounds derived from dicarbolic acids. Unlike lacquers, enamels have a natural shine. They require no sanding, polishing or buffing, and they provide far greater durability. Most contemporary higher-end commercial automobiles (as of Spring, 2010) have a two or three layer enamel paint-job with an outer layer of enamel clear-coat. Car enthusiasts rarely use enamels, either pigmented or clear-coat.