Water distiller cleaning crystals remove stubborn water scale residue. Long lasting 16 Ounce Jar (453 Grams). Made primarily of citric acid mono-hydrate which exists in all plants, especially in lemons and limes. Removes any stubborn residue and scale remaining in the boiling tank. Instructions: Fill 1 gallon stainless steel boiling chamber with water to fill line as normal and add 1 1/2 tablespoons Cleaning Crystals. (For 2 gallon Durastill or other brand boiler, use 3 tablespoons.) LEAVE TOP OFF and turn unit on until water just begins boiling. Turn unit off and wait 20 minutes to 1 hour depending on amount of water scale. Discard water and rinse interior well. (If used in a plastic boiling chamber, do not turn unit on to heat.) NOT SUITABLE FOR FOOD USE. CAUTION: MAY CAUSE SKIN, EYE AND RESPIRATORY TRACT IRRITATION. KEEP OUT OF REACH OF CHILDREN.