Q.: Someone threw an egg at my car while I was shopping. It splattered on the hood and windshield and some of the egg ran down into the holes beneath the wipers at the bottom of the windshield. It was a very hot summer day, and it took me about two hours before I got home to get it all washed off.

I have heard that eggs are very hard on car paint and “eat” it, and that it might take some time for the damage to show. Is this true? Is there anything I can do to avoid future damage? The car is about 10 years old, and the paint looks very good all around.

Also, is there any damage from some raw egg running into what I think are vent holes at the bottom of the windshield and the back of the hood? Hopefully my washing water cleaned it out. Where does that water go down those holes? In winter, am I going to smell rotten eggs when I turn on the heater?

A.: Eggs are very tough on vehicle paint as they contain sulfur, a component of two amino acids. Once applied to paint, it can take only a short time when baked by the sun to etch or craze a vehicle’s clear coat finish. It sounds like you were fortunate to avoid noticeable damage, perhaps due to a good coat of wax and prompt action.

Removing dried egg can be difficult without causing paint damage. Home remedies include soaking a soft towel in a solution of half white distilled vinegar and half lukewarm water or Vaseline Intensive Care Lotion and covering the affected area for a few minutes prior to gently working at the deposits.

Egg down the ventilation intake won’t damage anything, but can lead to some foul odors later. It sounds again like your flushing of this area with water was successful. The air intake typically drains either under the vehicle or outside-firewall, so it’s OK to flush it with a medium rate or less with the garden hose. I believe if you haven’t seen any paint damage after your cleanup or haven’t noticed any ventilation odors, you have nothing to worry about.

Speaking of sulfur, I learned from a reader that my advice to clean a keyless entry fob’s battery terminals with a pencil eraser was OK if it’s a white eraser, but not a red one. It seems pink- and red-colored erasers contain sulfur and rubbing it on silver contacts can form silver sulfide, which is a nonconductor. This fix would last a few months at best.

Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose. E-mail questions to under-the-hood@earthlink.net.