If we have a good olive harvest, we generally fill these 25-litre containers when we mill the oil. They are a bit of a pain to clean but I’ve found a good method to ensure that they are ready for next year.

1. Use an outside hose to rinse out as much oil and sediment possible.
2. Bring inside.
3. Fill the kettle and bring to the boil.
4. Meanwhile, fill the container to the 1st line with cold water and some washing-up liquid.
5. Put on the lid and shake well.
6. Clean the outside of the container with washing-up liquid and a sponge.
7. Empty.
8. Rinse with cold water.
9. Fill the container to the 5th line with hot water.
10. Put on the lid and shake well.
11. Leave until the kettle is ready and then undo the lid and empty.
12. Pour the boiling water into the container.
13. Shake well.
14. The container will expand with the steam, so gently release the pressure by undoing the lid, covering it with a dishcloth.
15. You will need to release the pressure about 5 times, shaking the container thoroughly after each time.
16. Undo the lid and empty.
17. Completely fill the container with cold water. Empty and make sure that the water runs clear. Continue rinsing with cold water if it doesn’t.
18. Fill the container with a small amount of cold water and add a minute amount of sodium meta-bisulphate to sterilise.
19. Replace the lid and leave until needed.