A Using a large metal spoon, remove and discard any scum from the surface of the marmalade. B Use a medium heatproof jug to pour the hot jam into jars; seal while hot. Label and date jars when cold. Store in a cool, dark place. 3 Push the jam with your finger, the skin will wrinkle if the jam is ready. If the jam is not jelling, return it to the heat and boil it again.