Decanters are a challenge to clean because of their long, narrow necks and small mouths. Old decanters are even harder to clean because unless they were carefully cleaned before storage, their insides could be badly stained with dried wine sediments. But this doesn't mean that cleaning them is impossible.
Pour a mixture of rock salt and white vinegar into the decanter and shake well. The rock salt will scrape off the dried sediment, and the vinegar will dissolve water stains and other deposits. Leave the solution in the decanter overnight for better results. Then rinse thoroughly with warm water.
Pour a mixture of baking soda and warm water into the decanter and shake well. The cleaning and oxidising action of the baking soda will help dissolve any stains in the decanter. Rinse well with warm water.
Pour warm water and then drop a denture-cleaning tablet in the decanter. The tablet should bubble as it reacts with the warm water and performs its cleansing action. Leave the solution in the decanter overnight, then rinse with clean water.
Use warm water and a splash of dish detergent. Shake the decanter well to clean the inside. Rinse thoroughly with warm water.
Use a bottle brush for really stubborn stains, but use caution in case the tip of the brush has exposed metal that could scratch the decanter.
Use a soft sponge dipped in a dish detergent solution to gently cleanse the outside of the decanter. Carefully scrub any decorative etchings and crevices. Dry well with a dish towel.
To dry the inside of a glass decanter without leaving watermarks, use a spray can of compressed air or a hair dryer set to low heat.