Zerox: getting pages white.
First of all, it helps if the paper is clean and flat at the start. Try drawing in a sketchbook, that helps. I also scan line drawings in grayscale. And, after that, many of my pencil lines have smudged anyway, so I use photoshop to clean up the image a bit. I also like to play with the brightness and contrast to get the lines darker, as grey is a tad too light.
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