1. Fill the bottom of the pan with a layer of water.
2. Add 1 cup vinegar.
3. Bring the pan to the boil. It should be looking a bit cleaner already.
4. Remove the pan from the heat and add the baking soda. Expect fizz!
5. Empty the pan and scour as normal; if necessary add an extra bit of dry baking soda.
6. If there are any super stubborn marks that don't come off with scouring, make a paste of 2tbsp baking soda and a couple of drops of water. Leave the paste on the marks for a while and return to clean as normal.
7. Now you can put your feet up and enjoy the many hours you saved yourself standing over the sink..