Letting water sit in the Raw Tea Kettle for long periods of time can form rust and mineral deposits over time. Fortunately, regular washing and deep-cleaning can help. To prevent rust and mineral deposits from forming in the first place, don't let water sit in the kettle overnight.Use Vinegar:Combine equal quantity of water and vinegar and fill about half kettle with the solution.Boil the solution in the kettle and switch off the kettle.Allow the solution to stay in the kettle for about 10-15 minutes. Pour the solution away and rinse.Rinse the kettle several times to remove any of the vinegar from the kettle.Use a clean cloth to wipe the kettle inside out. Allow it to dry.After the kettle dries, boil water in the kettle once again to remove the remaining traces of vinegar completely.Use Lime or Lemon Water:Prepare a mixture of about 500 ml (2 cups) of water and about 30 grams (1 oz) of lime or lemons.Boil the prepared mixture in the kettle for about 20-25 minutes.Empty the solution from the kettle. Allow it to cool down.Wipe the remaining hard water residue from the kettle using a small amount of soda bicarbonate on a damp cloth.Rinse the kettle at least 4-5 times with fresh water before using it again.Use Lemon Slices:Slice fresh lemons after juicing it.Fill the kettle halfway with water. Add the extracted lemon juice in the water and place the lemon slices on the top. Boil for 15 minutes and leave to soak until the water cools down.Remove the lemon slices and drain the water from the kettle. Fill the kettle with plain water and boil again for another 10-15 minutes.Rinse the kettle thoroughly and wipe with a soft clean cloth.Source: bestelectrickettles.netRefer to the Raw Tea Kettle GKD-450 user manual for more information.