3/4 cup sugar per cup prepared fruit
Squeeze juice from fruits. Save the pulps and tie in a muslin bag. In a food processor or a meat grinder) grind the fruit peels and pulp.
Measure juice and ground fruit together; add 1.5 times its volume in water. Bring fruit and water to a boil in a non-reactive (enamel or stainless steel) pan and boil. Boil until mixture is reduced to half its original volume.
Add to this mixture 3/4 cup of sugar for each cup of fruit.
Stir and bring to a rolling boil (i.e. a boil which cannot be stopped by stirring).
Reduce heat to maintain a fast simmer. Stir occasionally and test for jelling after 20 minutes. Marmalade is done when a skin forms on the test sample after about five minutes.
If you are in doubt, turn up the heat and bring to a fast boil for 5 minutes. Test again. Ladle mixture into preheated, sterilized jars. Cover with beeswax or paraffin