Paint 101: What You Need to Know
There are two kinds of car owners in the world. One thinks the greatest advance in automobile history was and always will be John DeLorean's paintless stainless-steel exterior on the DeLorean DMC-12. The other is people who lovingly coo Bread's "Baby I'm-A Want You" (or maybe 2Pac's "I Ain't Mad at Cha") while hand-buffing their ride's multilayer clear-coated finish.
For all the attention lavished on car paint, almost no one knows what this essential material is even made of.
First, some basics.
There are two primary types of car paint — water-based and solvent-based paints. Both use a liquid that holds the pigment in suspension so it can be sprayed. In both cases, the liquid evaporates, leaving the pigment behind. Pigments are ultra-fine or nano-scale natural and man-made particles that are a paint's color.
Solvent paints use a resin to hold the pigment in suspension and to help the pigment stick to the car body. A solvent is added to dilute the resin and pigments so they can be sprayed.
Water-based paints, on the other hand, use additives like binding agents, but use few or no solvents. Water dilutes the pigment and carries it to the car body.
Solvents have been a part of car paints going back to Gottlieb Daimler and Karl (Carl) Benz, making coats ever faster to apply and more durable. They also have been fouling the environment and sickening people due to exposure for just as long.
Water-based (sometimes called latex) paint is a relative newcomer to car fenders. It wasn't until the Clean Air Act amendments of 1990 that paint-makers began adding water-borne paints to their product lineups, and even then, it was in response to clean-air initiatives to cut volatile organic compound emissions.
On the surface, water-based car paint seems counterintuitive. Ordinarily, fine particles sprayed onto a car with water are called mud, and dried mud readily comes off the car with more water.
Water-based paint uses special particles that are like tiny meatballs, albeit meatballs coated with Velcro, that are held apart by water. As the water evaporates, the meatballs bump together and hook onto each other to form a layer of paint.
The binders or polymers in solvent paint are more like microscopic strands of angel hair pasta. As the solvent evaporates the polymers lace together, locking onto each other and the car body, sort of the way noodles glue themselves to plates left unwashed after an otherwise enjoyable dinner party.
In fact, once dry, the two types of paints compare favorably.
Both are equally durable, although that is the focus of online debates. Major U.S. paint-makers, including DuPont, tout their water-based auto paints, citing a number of factors, but they avoid durability claims.
It costs about the same to paint a car with either one. On a per-unit basis, water-borne paint can cost slightly more, but it can go as much as 50 percent further than solvent-based paint. That's a savings not only of materials but also of time, as painting each car is faster, according to DuPont, maker of Standohyd waterborne base coat.
Water-based paint can be more finicky when it comes to drying, requiring a greater degree of climate control than its competitor does. Guns used for solvent-based paints, common tools in the industry, can't be used to apply water-borne paint. But cleaning water-borne paint guns requires only warm, soapy water rather than the solvents needed for solvent-based paints.
Environmentalists (who nonetheless also want a spiffy car) can feel good about water-based paint on their vehicles. As water shortages become more frequent, water-based paint may be viewed differently. The specific act of coating a car with solvent-based paint — excluding the production of the paint and the viability of recycling paint waste — can be done cleanly, but for an ever-steeper price.
The deciding factor when choosing how to finish your car is largely personal taste (and influenced by the fact that no one's making DeLoreans anymore).