You've all seen commercials and films where the entire street or parking lot appears wet and glossy. How is this done? I'm guessing that water evaporates too quickly to get the entire street evenly. Do they use some kind of glycerin or glycol? A really good example of this was in "X-Men, First Class" when they went to the third floor parking garage. The entire floor looked like it was coated with some kind of glossy liquid plastic.

There's no secret sauce here, just a water bowser and bit of backlighting. Simple really.

Water truck.

connect a hose to a tap (faucet).
hold free end of hose.
turn on tap (faucet).
wave around the hose when the water comes out.
repeat when evaporation occurs.

You've all seen commercials and films where the entire street or parking lot appears wet and glossy. How is this done? I'm guessing that water evaporates too quickly to get the entire street evenly. Do they use some kind of glycerin or glycol? A really good example of this was in "X-Men, First Class" when they went to the third floor parking garage. The entire floor looked like it was coated with some kind of glossy liquid plastic.

You can't use anything like glycerin. You will create a high risk for slips and falls.

The answer is to use a water truck that can wet the entire street down in a quick pass. When it starts to dry off enough you send them back for another pass. Depending on the weather you may have to wet it down every 15 minutes.

If its a small space you can do it with a garden hose. Otherwise you really need a water truck with a boom sprayer on the back.

Yup as said it's a simple as a water truck (or a friendly local fire truck for hire) and wet it before you do some takes, you also need to light the water so it shines.

This also goes for rain effects, the key is to back light the water so it shows up on screen.

Our fire brigade connected up a fire hydrant and supplied a fire hose for creating a rain effect on one production I worked on. It would work equally well for wetting down a reasonably sized area.

Thanks guys, but I thought it was something more complicated than that because all the scenes I've seen don't have puddles or dry spots. Everything is evenly and completely uniform in dampness, something I haven't been able to replicate when doing a large area with just water.

Its really no magic to it other than water. You would have crew sweep any puddles to break up those shiny spots.

Other than that it comes down to lighting.