“Scary sharp”—sharpening on sandpaper adhered to glass—works really well, but one thing has always bothered me. I’ve tried spray adhesives as well as PSA (pressure sensitive adhesive) backed sandpaper. In both cases, I’ve found that the sheets are very difficult to remove when they’re worn out. So is the glue residue.
When I was a kid, I built kites using paste made by mixing flour and water. I’ve tried this method on my sandpaper, and the results were just what I wanted. The paper sticks to the glass very well; wetting it slightly makes it easy to remove.
To make the glue, mix flour and cold water to the consistency of paint. Use a brush to spread the glue on the sandpaper, then press the sandpaper firmly onto the glass. Place a sheet of wax paper on a flat surface, then place the glass on top, sandpaper side down. Let the glue dry for 10-15 minutes.
When you remove the sandpaper to apply a new sheet, you can easily clean off the paste residue with water. Or, you can spray a little water on it, let it soak for a minute or so and re-use it. –Alejandro Balbis