Take out a blender and insert the ice cubes from two ice cube trays. Blend only until the ice cubes are about 1/3 of their original size. Don't make the pieces too small.
Transfer the crushed ice cubes to your glass coffee pot. Add 1/2 cup of vinegar and 1/2 cup of rock salt.
Swirl the mixture around inside the coffee pot for several minutes by holding on to the handle. There is no need to use a spoon to stir it. The swirling motion is enough to get the ice, vinegar and rock salt to do their jobs.
Dump the contents of the coffee pot out and rinse it clean with either distilled or purified water.
Dry the glass coffee pot off with a paper towel.