Well, at first I thought window, but with the clue, I'd have to say water. Like your hot tub, for instance. That's my best guess.

Vicki "FuhKaui" guessed:

A throw blanket held up to a window with Holly's hand holding it up from the outside.

Heather M. gussed:

Bleaching a piece of fabric in a front-loading washing machine? They just had an article on fading fabrics in Martha Stewart Living last month. :)

Jin B. guessed:

A piece of fabric on a glass top table (picture taken from underneath) back lit by a bright light...?

Wendy D. guessed:

Some random scrap of hippy fabric (or some Indian batik thing that small children went blind making), that you taped to the patio doors one morning when the sun was shining brightly. Keith was outside, and, for the second shot, put his left hand on the glass. The third pic was taken after the sun went down.

How's that for a guess?