Lancelot's Unwelcome Hitchhiker

This week on Car Talk, Tom and Ray heard from Lancelot (no, not THAT Lancelot), out in California. Recently returned from the humungous and somewhat eccentric Burning Man Festival, Lance discovered that he returned home with an unanticipated hitchhiker: a mysterious alkali residue, courtesy of hours of driving through the salt flats.

You can Lancelot's call with Tom and Ray -- including scintillating details of Burning Man -- right here.

Lancelot's problem? The stuff won't wash off. Tom and Ray's suggestion was to find a neutralizing agent, like white vinegar. Head over to the most inconspicuous part of the vehicle, and try a test on a small section of the car's body.

But, our humble hosts -- and certainly Lance -- want to hear from you, too. Got any suggestions for removing pesky salt stains from the side of your ride? Share your suggestions right here. Thanks!

I’m concerned about your solution to use a mild acid like vinegar (acetic acid). The problem is that to neutralize an alkaline material with an acid, you have to mix just the right amount of each. If you use too much vinegar, it should neutralize the alkaline residue, but would leave an acidic residue from the excess vinegar, and that’s likely just as corrosive as the alkaline residue.

I would try just rinsing well with water.

Wikipedia says that the alkli at Black Rock Desert in Nevada, where Burning Man is held, is mostly gypsum, which is calcium sulfate, which will have a pH between 7 and 10 depending on the amount of water absorbed by the crystals. Other common salts in alkali deserts are sodium carbonate, calcium carbonate, and sodium borate, all of which are basic or alkali. They also have low solubility in water.

Anywhere in the Northeast US, car owners encounter acid rain, due to the area being downwind of Ohio valley coal-burning powerplants that put acidic pollution in the air. One of the main arguments for using special car wash soap rather than dishwashing liquid is that car wash soap is pH balanced to neutralize acid rain (i.e. slightly basic).

So I think car wash soap would not be very effective on alkali salts. I might try diluted vinegar to remove the salts, followed by a hand washing with a car wash detergent that advertises itself as pH balanced to prevent acid rain damage, to neutralize the vinegar.

I had the same problem after visiting a friend on a ranch in drought-stricken central Texas. And I tuned into Car Talk this past week at the precise moment that this question was being asked. First, I used straight vinegar, and it took it off in layers and was especially effective on the glass. Followed closely, of course, with a mild soapy wash. I’d been visiting this friend on and off for a couple of years and didn’t realize what was going on. I was cursing Toyota, thinking the paint job was peeling and no good. It was the caliche. What really turned the trick was 3 coats of paste wax. With the second coat I could tell it was moving the discoloration around, and on the third coat I experimented with small areas and removed all the built up caliche. I don’t know if the vinegar is essential. It probably loosens it up. But the paste wax – and a LOT of elbow grease – got it off.

Actually, waxing the car is not a bad idea… I just would have used one coat of a cleaner was, not 3 coats of paste wax. Or one of the clay bar products, followed by one coat of paste wax.

In that area it is either Gypsum, Aragonite, or a mixture of both. Diluting a little vinegar in water and washing your car with it should take it off. I would follow with a thorough rinse afterwards to make sure you don’t leave a damaging acidic residue on the car.

Lance-alot was incorrect. Burning Man exceeded its sold-out and
BLM Permit-limited capacity of 50K by 4K.
They are looking to get Bigger! a “Woodstock for art”? That only happened twice, this is an excess that is unsustainable-it went on during Katrina and uses up warehouse loads of lumber. Burners have a run on supermarkets and Wal-Mart, like locusts.

Gypsum “salts” (not like the Utah desert) are slowly soluble in water, if vinegar is used it should be dilute and followed by baking soda to neutralize.
Gypsum flocculates (clumps); I suggest the pre-soak solution at the car wash,
with a biodegradable soap or dilute sulfonic acid, followed by the
’no-spot’ rinse. This is (in theory) deionized water.
Consult a soil chemistry text.
Burners are proud of their “dust” and leave it on for days,
at least Reno is saved some water by this.

Unfortunately, it sounds like Lancelot has already attempted to wash the car. Vinegar is great for neutralizing alkali dust on your feet (where it may eventually lead to mild burns), but isn’t going to do much to get the dust off your car.

The trick is to brush as much as you can off with dry rags (vacuuming as you go) before you get it wet. Once playa dust gets wet it turns into fine mud and seeps into all the little cracks and surface irregularities in the interior panels. Once it’s gotten wet, I’d recommend getting a brush with fairly stiff bristles (as stiff as you can get without risking damage to the interior) and really scrubbing it. Soaps/acids/waxes might help some, but physically brushing it off will go a lot further than cleaning chemicals.

On the exterior, it’s not as big a deal since the painted surface is pretty smooth. It’s still better to brush it before getting it wet, but repeated washing should get it off the exterior.

Burning Man has a link for everything. Here is what they say about taking care of your car after “the burn” which, BTW, was 50,000 this year! From the website:


If you drove your car to the playa, wash it as soon as you can after returning home, because the alkaline dust can corrode your electronics, and do damage to your upholstery, plastics, etc. Before you do anything, get an air compressor (or go to the air station at your local gas station) to blow all the dust off your engine. (Unless you really know what you’re doing, don’t spray water on your engine, as it can damage your sensitive electrical components.) Then, put on a pair of goggles, open all the windows, and turn your AC fan on high. Then switch your temperature control from cold to hot on ALL your different vent options, including both recirculating the air and not. This will start to get all the dust out of your vents.

Then wash your car with a splash of white vinegar in the soapy water. Vaccuum the hell out of it with the strongest vaccuum you can find, and then use Armor All on your plastic and leather parts, as it cuts the alkaline playa dust really well.

So you can do all this, or (be lazy like me and) take it to a professional car wash place. In San Francisco, they recognize playafied cars, and take extra steps – and charge you for them – to wash your car thoroughly, usually running it through the machine twice, and applying extra elbow grease to your playafied bits. It’s worth the money.

<and, there are discussions/forum on their site, too>

Hope you enjoyed your first burn!