We Sand Off As Much Paint Off As Possible. There Are Surfaces Where Our Sanders Cannot Get into Such As: Between floor-boards. After sanding you might see a very faint line where the previous paint could not be sanded off. Typically this will not be visible after deck is re-stained. Inside knots, again, sander cannot get deep inside wood knots. Re staining deck will hide these remnants. To sum up- we remove 90 to 99 percent of previous stains, any remnants can be easily covered with new stain/sealer, or even a solid stain.