I had shellac taken off and new applied. For the taking off they used a machine file that scratched off parts of my actual nail. I told them it's unnecessary as I had CND before and it was almost falling off on its own once you apply nail polish remover, but they explained it was the way they do it. As I only do shellac occasionally, its frustrating as once I remove the current shellac, my nails will be visibly damaged for a good few weeks, meaning I need to put polish again until the scratches grow out...