Wash and rinse your jars and lids well with warm, soapy water. Line a roasting tin with a clean cloth, and place your clean jam jars upside-down on the cloth. About half an hour before potting your jam, place your jam jars in a preheated 100 C oven.
Meanwhile, place the clean lids in a large pan and cover with water. Boil for 10 minutes to sterilise the lids. Also boil any other utensils - such as a funnel or spoon - at this point.
When ready to pot your jam, remove the jars from the oven. Using an oven mitt, turn your jars right side up, keeping them in the roasting tin. Pour your hot jam into the warm jars. Make sure to leave a 1cm headspace in each jar.
Place the lids on the jars straightaway. Allow to cool thoroughly at room temperature, then store in a cool, dark place for up to 1 year. If you can press down on the centre of the lid and make it move, the jar is not properly sealed: refrigerate and consume within two weeks.
Learn how to sterilise jars two ways with our handy step-by-step guide and video.