Wash jar, lid, and screw band in hot soapy water, then rinse well. Dry screw band. Put empty jar on a rack in a boiling-water canner or a deep 5- to 6-quart pot and add enough hot water to cover by 2 inches. Bring to a boil, covered, then boil 10 minutes. Remove canner from heat, leaving jar in water. Heat lid in water to cover by 2 inches in a small saucepan until thermometer registers 180°F (do not let boil). Remove from heat. Keep jar and lid submerged in hot water, covered, until ready to use.