Zelazny's Waterproofing

You permanently render one object you touch impervious to water. This works on fabric, leather, canvas, wood, and similar materials. Water can't penetrate the treated surface, so the contents of a treated container remain dry, and the effect isn't diminished by immersion or prolonged exposure to moisture.

The object must be unattended or willingly offered by its holder, and no larger than what you could fit in a 10-foot cube.