Sterilizing and Sealing Jars

Containers for storing preserved foods must be sterilized to kill micro-organisms—only heatproof containers may be used. Wash glass jars in detergent and water, then boil them in water for 10 minutes. Dry them upside-down in a warm oven. The rubber gaskets for clamped jars should be covered in simmering rather than boiling water. They may be used once only. Alternatively cover the jar with a screw top (dome lid and metal cap). Fill jars to within ⅛ in/3 mm of the top. Jars without lids need ½ in/1.25 cm headroom for sealing with paraffin.