Bring the jam to a boil - tumble without glasses
Homemade jam is, quite rightly, still very popular. For the preparation, there are now a lot of recipes, but a "problem" appears again and again.
I mean the "tumbling" of the screw jars after filling, I think that is completely superfluous and would like to explain why.
The origin of the fall comes from the tin cans with paint, the lid is usually slightly deformed when opening and then pressed again. Then the rifle is turned around for a moment (and then back again), creating a film inside that seals the edge.
This is unnecessary with jars for jam, there is nothing to dense!
If the marmalade is filled in hot and the lid is screwed on as soon as possible, a negative pressure forms on cooling. This seals the lid.
Incidentally, an air layer of just under a finger should remain wide, this air is sterile, even without "pervading" through the jam.