Minerals, salts and the elements often cause a white build up on your terra-cotta pots. To remove the residue, left from a long winter, on your clay pots, combine equal parts water, white vinegar and rubbing alcohol. Pour into a spray bottle and gently shake. Spray the mixture onto each pot generously and scrub with a plastic brush. After deposits are removed wipe with a watered cloth. Let the pot dry before you plant anything in it.