Trying to figure out how to cheaply duplicate those fancy seed starting systems they sell in Gardener's Supply. Basically, you set the trays on a low platform set in a flat filled with water. There's a capillary mat that covers the platform and drapes into the water, keeping the mat constantly moist and transferring it evenly to the trays. Anyways, I've got just about everything figured out except for the capillary mat. What would be a good, absorbant, resuable material to use for this?