Exfoliate your car to extend the life of its finish? Tom and Ray demystify claying

Dear Tom and Ray:

So I'm thinking of getting my car detailed, and an associate gives me a referral. While perusing the service sheet, under "Options" is listed "Claying, add $30-$40." I'm thinking, "Holy spa treatment, Batman!" The other side of the service sheet explains the process: "Why clay your car? Claying your car produces dramatic results. Using a lubricant spray, clay is slid alongside your paint. It picks up microscopic pollutants, which a car wash cannot remove. The result is stunning! Your paint looks cleaner and feels much smoother to the touch. With a coat of wax, your car will look the best it ever has." So my multipart question to you: Have you ever heard of this; what do you think; is this for real?
-- Claudia

Ray: Do they lay slices of soothing cucumber over your headlights, too, Claudia?

Tom: Believe it or not, this is for real, Claudia. We'd never heard of it. But we checked with our pals in the bodyshop underworld, and they say it's a procedure that's been accepted for a long time. It works sort of like Silly Putty works when you press it against a newspaper. Small particles stick to the clay, and then are pulled off the car's finish.

Ray: Apparently it's one of the methods used to remove rail dust from cars. Sometimes new cars that are transported by train get covered in a fine coating of metal dust that's created by the interaction between the train wheels and the tracks. And removing the dust by traditional methods can scratch the surface.

Tom: Claying is also said to remove acid-rain stains. And ring around the collar.

Ray: Is claying necessary? Of course not. It would be the kind of thing that someone who is very particular about her car's appearance would do. And if you're keeping a car forever, I suppose it might very well prolong the life of the finish.

Tom: Hey, while they're claying the car, do you think they could reshape it? Maybe they can clay my '78 Fiat and make it look like a Ferrari.

Ray: You'd be lucky if they could reshape it and make it look like a car again.

(Car Talk is a nationally syndicated column by automotive experts (and brothers) Tom and Ray Magliozzi. Write to them at the Car Talk Web site.)