To sterilize jars and lids either take them straight from the dishwasher or wash in hot soapy water. Then pour boiling water into the jars and onto the lids (put lids in a heatproof bowl) and heat for 20 minutes in the oven at 120°C. Leave jars in oven until jam is ready. Lids should be left to drain or can be put in oven to dry off once you've turned off the heat with just the fan running.