Soda crystals

A tablespoon in hot water cuts through cooking grease on hobs, extractor filters and the tops of kitchen cupboards where the film goes sticky.

Also the standard soak for burnt pans and for cloths that have gone stale: overnight in hot water with a spoonful.

Wear gloves. It is alkaline enough to dry and irritate skin over a long job, and it will dull aluminium on contact.

Not on aluminium, unsealed wood or painted surfaces. Never combine with an acid in the hope of extra power — they cancel each other out and you are left with salt water.