Q. There are splashes of concrete on the rear wheelarch and passenger door of my Mercedes A 140. I’ve taken it to a hand car-wash company and I’ve tried to remove the splashes myself using white vinegar, but to no avail. Is there a way to remove it without grinding it off?
A. It may be possible but it will require time and patience to do so without damaging the paintwork. You’re on the right lines with white vinegar, which should be mixed with an equal amount of water and put in a spray bottle for convenient application. However, simply spritzing the solution on and hoping for the best is not enough.
Before you start, block off the surrounding area with masking tape or paper to prevent accidental damage to unblemished paintwork as you work. Then thoroughly soak the concrete patches with the solution. It can help if you hold a damp cloth over the offending area, respraying it every minute or so and allowing each application to soak in.
When you are satisfied that the liquid has penetrated, gently poke at the concrete — through the cloth — with a plastic or wooden kitchen spatula. With luck you’ll see a few bits of loose concrete appear on the cloth. Remove this carefully, apply more mixture and press the cloth onto the concrete again. The idea is to lift off thin layers of concrete a little at a time. Avoid rubbing, as this could damage the surrounding paintwork.
When you’ve got as far as the last few fine grains, use a clay bar to remove them. This is a soap-bar-shaped block of putty-like material that helps lift off fine particles of debris. Try Bilt-Hamber Auto-Clay (£11.95 from theultimatefinish.co.uk), which can be softened with water to make it more pliable. Wetting the area can help with this too, though some types of bar come with their own lubricant.
Once all traces of the concrete have disappeared, apply a high-quality bodywork wax such as Autoglym’s HD Wax (£44.99, halfords.com).
Dave Pollard has written several Haynes manuals and has tested just about every car-related accessory – read more from Dave here.
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