To remove scale
To remove scale from boilers and any other pans used to boil water, fill them with 2/3 vinegar and 1/3 water and a handful of salt. Boil for a few minutes, turn the stove off, let it stand for 12 hours and rinse before use. Increase the water quantity and reduce the vinegar quantity to remove scale stains from aluminium teapots and pans. To remove scale stains from stainless steel, dampen a sponge with warm vinegar.
Thermos flasks have a stale smell if they are kept closed for a long time. Wash them with hot water and vinegar and rinse with cold water.