Has anyone heard of 'paper negatives'? Yes, the light goes right thru the paper and will reflect off the easel. Kodak described making photo-copies with singl weight grade 5 paper back in the 1940's, place the paper face down and expose thru the back, produced a reversed negative photo-copy that could be read in a mirror or contact printed. You could try Ralph's experiment with a Sharpie on the back to see how this affects your set-up. Using a flat black easel removes the variable re-exposure of the print and should increase sharpness and fine detail.