Ideally, you shouldn’t cut over anything but clean glass. Before you cut it, you need to clean your bottle thoroughly to remove any dirt, dust, or debris, including labels and the adhesive beneath them. Cutting through a label and the adhesive that adheres it to the bottle will dull your blade, causing you to have to replace it sooner. Your cutter won’t last as long and you certainly won’t get your money’s worth. A dull blade won’t score your glass properly, which can also lead to cracked or broken glass, rather than a clean cut.