Fortunately, the Netherlands has overcome the initial shock and enthusiasts are buying classics again. A new enthusiast asked if he could get his classic convertible through the car wash.
We say: don't. Certainly not when the convertible top has a plastic rear window. The hood itself is not fond of this kind of modernity either.
Wash the hood, out of the sun, with a mild soap, green soap is fine, and lots of water. Rinse the hood explicitly, but not with the high pressure cleaner.
Then let the hood dry. Never fold a wet convertible top. This results in fungi and mushrooms.
Green soap is very bad. This is an organic (non-synthetic) soap which means that you can get mold in your hood. The best thing is just lukewarm water, possibly with a little (synthetic) washing-up liquid.