Egg Shell Soda

• 18 egg shells
• 70 ml (2½ fl oz) cider vinegar
• 300

Remove the film from the egg shells and put the shells into a saucepan. Cover with water and bring to the boil to kill any bacteria. Simmer for 5 minutes then drain.

Preheat the oven to 180°C/350°F/Gas Mark 4. Put the egg shells into a roasting tin (pan) and