Wash the plums, cut them in half and remove the seeds. Boil the water with sugar and cinnamon sticks and then let cool. Put the plums into prepared jars and pour the sugar solution over them. Seal the jars with rubber ring, lid and clamps. Place the jars in the fat pan in the oven preheated to 175°C and pour so much cold water into the pan that the jars are about 2 cm in the water. Wait until the liquid in the jars bubbles, this takes about 40 minutes.
Turn off the oven now, but it will stay closed. Leave the jars in it for about 30 minutes.
After the boiling time, remove the jars, just let them air dry. Remove the clamps only after they have cooled down completely.
