Photo showing a saucepan of boiling plum and strawberry jam, being stirred on the hob with a wooden spoon and allowed to simmer away, some that the jam reaches its setting point and can then be ladled into sterilised jam jars, allowing it can cool down as set like a jelly. A knob of butter is pictured on a white plate, being scraped / added to the hot jam to disperse the remaining scum from the hot mixture.