it slowly forms crystals and freezes. also blow some bubbles up into the air, as high as you can so they have a lot of time to freeze before they land. watch how they react as they float, hit objects such as branches, and land on the ground. typically, they will not react the way normal soap bubbles do at all.
you can use commercial bubble solution or homemade, and people have reported that both work about equally well. obviously, a better quality solution will have a better chance of holding up long enough to see results.
kids will notice that the bubbles begin to form crystals as they freeze. they also 