If you see water beading up, your car's waxed finish is fine.

Dear Car Talk | Jan 01, 2002
Dear Tom and Ray:
RAY: The other day, my brother went into a place that advertised waxing. But he fled in horror after they asked him what kind of bathing suit he was planning to wear and if he wanted his back done, too.
TOM: You're in good shape, Wally. If you can see water beading on the hood, then you've got wax on the car. And you're right that it will help maintain your car's appearance.
RAY: Generally speaking, the spray-on waxes you get at the car wash don't last as long as the better waxes that you apply by hand. But in your case, since you get your car done once a month or more, that shouldn't be an issue.
TOM: Just watch for the beading water. As long as you see those nice, large beads, you're all set.
RAY: And don't be so pessimistic about the future, Wally. I have a feeling you're going to be looking at those 2015 Cadillacs.
RAY: The other day, my brother went into a place that advertised waxing. But he fled in horror after they asked him what kind of bathing suit he was planning to wear and if he wanted his back done, too.
TOM: You're in good shape, Wally. If you can see water beading on the hood, then you've got wax on the car. And you're right that it will help maintain your car's appearance.
RAY: Generally speaking, the spray-on waxes you get at the car wash don't last as long as the better waxes that you apply by hand. But in your case, since you get your car done once a month or more, that shouldn't be an issue.
TOM: Just watch for the beading water. As long as you see those nice, large beads, you're all set.
RAY: And don't be so pessimistic about the future, Wally. I have a feeling you're going to be looking at those 2015 Cadillacs.
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