Every summer, a haze of fine Saharan dust settles over South Florida and leaves a gritty film on cars that looks harmless and is not. Here is what the dust actually does to paint and glass, and the right way to wash it off.
Most years, somewhere between mid-June and early August, the sky over South Florida gets a little duller and the sunsets get a little more orange. That is Saharan dust, a layer of fine mineral particles that rides the trade winds across the Atlantic and settles over the state for days at a time. It is a normal part of the summer here, and most people only notice it because of the haze. Car owners notice it for a different reason. It leaves a fine, gritty film on paint, glass, and anything else left outside. That film looks like ordinary dust, but it does not behave like ordinary dust, and washing it off the way you would wash off pollen or road grime can do more harm than leaving it alone for a day. What Saharan Dust Actually Is The dust originates over the Sahara Desert and gets lifted miles into the atmosphere by strong winds, where it travels in what meteorologists call the Saharan Air Layer. Every few days during the season, a new plume crosses the Atlantic, and some of it settles over Florida. The season typically runs from around mid-June through August, with the heaviest outbreaks arriving from late June through early August, right before the dust tends to taper off as peak hurricane season approaches. Mineralogically, it is mostly fine silica and clay particles. They are light enough to stay suspended in the air for days, but hard enough to behave like very fine sandpaper once they land on a hard surface and get pushed around. Why It Is Harder on Paint Than Normal Road Film Ordinary road grime is a mix of organic residue, rubber dust, and softer particulate that a normal wash breaks down without much trouble. Saharan dust is mineral grit. If it gets touched dry, or wiped with a towel before it has been rinsed off, the particles roll under light pressure and leave fine scratches in the clear coat. On a dark color or any high-gloss finish, those marks show up later as a web of fine swirls once the sun hits the panel at a low angle. Glass takes the same damage. A quick dry wipe of the windshield during a dust week is one of the more common ways people end up with a permanent haze that a normal wash will not remove. How to Wash a Dust-Covered Car Without Making It Worse The order of operations matters more than the products. A few adjustments to a normal wash routine make the difference. Rinse before you touch anything. Use a hose or pressure washer to flood the surface and float as much grit off as possible before a mitt or towel ever makes contact. Skipping this step is where most of the scratching happens. Add a foam or soap pre-soak. Letting a foam cannon or a heavily soaped surface sit for a minute or two helps lift particles that the rinse alone did not carry away, so there is less for the wash mitt to drag across the paint. Wash with a soft mitt and plenty of lubrication, top to bottom. Use a clean, dust-free mitt, work one panel at a time, and rinse the mitt often. Do not reuse a mitt that has already picked up grit on a fresh panel. Dry with a clean microfiber towel, or let it air dry. Pat rather than drag, and use more than one towel if the first one starts to feel gritty. Clean the glass separately, with its own towel. Mixing a dust-covered towel between paint and glass just moves the