Make your mark on metal.
Personalise your keys, tools, and cutlery with a battery, vinegar and salt.
Mix some salt and vinegar in a glass, and dip in the end of a cotton bud. Connect the positive terminal of a battery onto your metal with some crocodile clips, and join the other end to the cotton bud. Press onto your metal and the reaction will slowly take hold. Use a template cut out of sticker paper to leave a sharp mark on your metal.