Wash peaches and dry with a clean tea towel to remove most of the fuzz - no need to peel the fruit. This took exactly 20 minutes to get to a setting stage for me, but time may vary depending upon the fruit. Sterilise jars by washing in hot, soapy water, rinsing (or running through a cycle in the dishwasher) and standing upside down in 120C oven for 15 minutes. Pour hot jam into HOT jars - otherwise the heat from the jam with crack the jars.