??? Cookie Sheet Fabric

Looks pretty silly but these aluminum cookie sheets have helped me with fabric prep before and clean up is easy, so why not?!  1 yard of white PFD fabric per tray having soaked up a Setacolor paint mixture that will when dry produce a  mottled base fabric for next weekends Fresno, California class called Media Mixer.  It's still quite wet so looks much darker than it will be.