METHOD:
1. Put coins into a bowl of vinegar, mixed with a little salt. Leave for a few minutes, then rub dry until shiny.
2. Using a 2p as a template, cut out nine card circles. Make nine foil circles – cut these a bit smaller. Soak the card circles in vinegar, mixed with a little salt.
3. Build up a stack in this order: coin, damp card circle, foil disc. Continue until you run out of coins. Make sure foil layers do not touch.
4. Take a wire and stick one end to the top coin surface. Take another wire and stick an end to the bottom coin surface. Add tape to secure the battery.
5. Connect the free ends of the wires to your LED.