Auto Know: The art of the car wash

From grade-schoolers raising a buck for the band, to Butch in the driveway with a hose and a sponge, the art of the car wash has been around for as long as ... well, as long as the car.

Some folks are meticulous about keeping their cars clean. Others wait for the next rainstorm to do the job.

But for those of who question Mother Nature’s detailing ability, what’s the best method for keeping a vehicle clean?

Does the TLC of a hand wash in the driveway outweigh the convenience and ease of the automatic/drive-thru wash? Not a chance, at least according to a 2007 study from the University of Texas at Arlington.

“The results are depressing, at least to the car owner who, up to now, has firmly believed in hand washing,” the study findings were summarized in part. “...Under the microscope, the paintwork (after hand washing) looked like a cratered landscape. The paintwork was deeply scored and scratched — the result of dirt and trapped sand particles.”

The two cars used in the study were each washed 25 times — estimated to be a year’s worth of car washes — one by hand, and the other by machine. After which the paint “scars” were examined by microscope on both vehicles.

“By comparison, the surfaces of the test vehicle washed with automatic car washing equipment appeared different,” the summary reported. “It was remarkably smooth, the result of evenly moving and rotating cloth pads and curtains.”

The study also suggested that the garden hose used by do-it-yourselfers in the driveway is unable to supply enough water or pressure to safely remove dirt without injuring the vehicle’s finish.

How often a car needs to be washed is a personal preference. But if birds, bugs or trees find your vehicle, it’s time for a good wash.

Experts say if left unattended — especially in the hot sun — acids in bird poop, bug guts and tree sap can cause paint to fade and do serious damage to the finish. And that was our call to action to test out a couple of theories ... on a $160,000 Audi R8.

Photo Gallery

  • Wheelbase Media

    A not-quite-white Audi R8 seems like the perfect way to test out a couple of wash methods.

  • Wheelbase Media

    Since the automatic car wash can’t see that it didn’t get all the bugs off, it sometimes doesn’t get all the bugs off. Hand power wins over tech.

  • Wheelbase Media

    Pretty much any physical contact with the paint surface can cause scratches, but when drying it helps to start with a clean towel. Unless it’s spitting out fire or gravel, the air dryer at the automatic car wash wins this round.

  • Wheelbase Media

    After two passes with the soap, the auto wash spits this stuff all over the car. Whatever it is — apparently wax — it smells great. And you never have to get out of your car. Two more checkmarks for the auto wash.

Hey what's in that goop?

While the University of Texas study indicates automatic/drive-thru car washes are the safest, thoughts of vehicle damage and the great unknown of what the heck is coming out of those spray nozzles makes every car owner squeamish at the wash entrance.

Sure, the colorful foam that looks like regurgitated cotton candy smells curiously nice when applied to your vehicle — usually like lemons or medicinal bubble gum — but what is it?

That “soap” is just a mix of Sodium Dodecylbenzenesulfonate, Neodol, a surfactant, a little added scent, and water ... all of which sounds like a mad-chemist’s evil cocktail, but is actually benign when mixed properly.

The first mouthful — Sodium Dodecylbenzenesulfonate — is a common ingredient in laundry detergent that helps to loosen the dirt when mixed with water. Neodol is widely used in common surface cleaners, and helps give the car a waxy protective finish. And the surfactant helps the water work peacefully with the detergent in the cleaning process.

The familiar conveyor-type car wash operates on an intricate system of lasers, mitter curtains, computers, scrubbers, nozzles, hydraulics, brushes and dryers, which is a design that has been around since the late 1930s and has been evolving ever since.

For the novice, mitter curtains are the long, soft, stationary strips of cloth that hang near the entrance of the wash tunnel. Scrubbers are the large, rotating cylinders with hundreds of small cloth strips attached to them. These rotate and a high rate of speed, up to 500 revolutions per minute, and would feel like a whip if you decided to roll down the window for a touch.

Older automatic washes typically built before 1980 used brushes made with soft nylon, but which often left “brush marks” on the vehicle’s paint. Newer washers built in the last 25 years mainly used cloth with a slight pendulum action to wash the vehicle. The cloth is less harmful to vehicle paint, provided it is frequently flushed with water to remove any grit from previous washes.

The more recent touchless wash systems use high water pressure to clean the vehicle instead of brushes, minimizing the chance of surface damage and lowering liability costs for car wash proprietors. The nozzles of each jet are arranged like a pinwheel and the incredible force of the water — up to 1,000 lbs per square inch — rapidly spins these wheels to create a circular pattern and the necessary scrubbing action.

These newer high-pressure washes can use 1,200-1,500 litres of water per car, or the equivalent of 60-75 of those 20-litre pails you might use at home. To conserve water and reload for the next wash, these systems usually have a pressure tank situated nearby to recapture and recycle the water through a filtration process.

Once the car is washed, a protective wax is often applied (it’s usually optional) that is different from over-the-counter wax brands because it is formulated to also work on glass, chrome and rubber, though it does not provide the same level of protection or help to cover up/repair tiny scratches as standard wax does. Old habits die hard, and the results of one study might not persuade Butch or the other driveway do-it-yourselfers from changing their ways. In our little experiment, the touchless car wash performed surprisingly well, but left brake dust on the wheels and a few bugs in the grille.

But one thing is clear: given the choice between potential hazards from birds, bugs and trees, or those from either type of car wash, always choose the latter.

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