Scratches on window glass and crystal can be removed or lightened by using non-gel toothpaste. Gel-type toothpaste is not as effective as non-gel type. Rub a little non-gel toothpaste in the direction of the scratch and gently polish it with a soft cloth. This technique will only work on hairline or very light scratches. If you can feel the scratches with your fingernail, then those are probably too deep to remove.