Sour cherries (or griottes in French) make the best jam of all fruit, and that has got to be true because no one would bother with the small sour cherries at all thinking of the work of removing the stems and pitting the cherries. Yes, it does take about an hour to pit 1.750 kg of the small sour cherry variety. A good cherry pitter ( same tool as the olive pitter) is necessary and so is a good show to watch on TV. Anyways, let’s say you manage this interminable task late at night, sprinkle the cherries (about 1.5 kg left) with 1.250 kg of sugar and refrigerate overnight. To pit sour cherries try pulling the pit out with the stem. If the cherries are ripe enough, it should actually slide out from the fruit, and you only need the tool as a back up.
In the old days, the tradition was to break the pits to find the almonds, wrap all this in a mesh bags and add it to the fruit in lieu of pectin. So go ahead with it, it works, unless you allow yourself to cut that corner and add a bag of pectin instead.
Add a lemon juice and the halves of the rind to a jam pan or your largest frying pan and slowly bring to a boil. Remove any scum (sour cherries don’t need produce much). Cook as long as it takes for the ” is your jam ready test”. Your jam is ready if a tiny teaspoon of jam will take on a cold plate instantly. It will take some time. Cool 10 minutes, stir, remove the lemon rinds and transfer into sterilized jars. Screw the tops on and turn the jars upside down for a while (so the fruit does not all float to the top of the jar).