when you use glass off a roll, blow off or shake out the last foot or so on the roll before using it. I had exactly enough for one layer left on a roll, so I put it down and wet it out. I now have little brown specs all through the last couple of feet of the board. fibers from the cardboard tube the glass is wrapped around. never expected it, never saw it till the glass was wet out, bummer. just FYI.