Wash your plums and allow to dry.
Halve or slice plums and remove pits.
Thoroughly wash jars and lids.
Pack plums loosely into clean jars. Add spices if using.
Add water and sugar to a saucepan and bring to the boil.
Pour hot sugar syrup over plums, fill to within 1cm of the rim.
Place lids on jars and seal (not too tightly).
Place jars of plums into very large pot and add water to just above the level of the lids.
Bring the temperature to 72-80oC and hold for 20 minutes.
After 20 minutes, turn off heat and remove jars using canning tongs.
Allow to cool for several hours. Lids should suck down and seal very tightly. If lid doesn't seal, repeat water bather step with a new lid.
If using lids and rings, remove the rings and ensure that the seal is tight. Always store these jars without the rings.
Store in a cool, dark place for up to 12 months. For longer shelf life, increase the amount of sugar used in the sugar syrup recipe.