Some women call this the old-fashioned method because it’s the one their grandmothers followed. No one denies that the jellies and jams are delicious, but making them takes more time and skill than the other types containing liquid or powdered pectin.
It is important to know when the jelly or jam has cooked enough. The safest way is to use a jelly, candy or deep-fat thermometer. The correct point for your altitude is determined this way: Note the temperature at which the mixture boils, then add 8°. That is the point when the jelly or jam is ready to remove from the heat. Or put a little jelly or jam on a small plate and set in refrigerator, removing the kettle from the heat. If the fruity mixture in refrigerator jells in a few minutes, it is cooked enough.