Alot of times when removing old covering the glue and color delaminate from the clear top suface of the covering, you can put a small amount if balsarite on a rag and wipe away the subborn stuff left behind, you can also use masking tape to remove some of it by sticking it to the spot and tearing it away, don't do the balsarite method of you are going to recover with transparent covering because it will leave some dye residue behind, and it will show thru