Liver of Sulphur eXtended Life Gel is formulated for extended shelf life, versatility and convenience. XL Gel is used to patina metals such as silver, copper, bronze, metal clay. XL Gelâ€™s shelf life is many times that of dry liver of sulphur. XL Gel is non - flammable. XL Gel may be used in its ready form by brushing it onto objects.