2 tablespoon of lemon juice for sweet cherry jelly, none for sour cherries.
About 3 to 4 cups of sugar with sweet cherries and 4 to 5 cups of sugar for sour cherries.
Directions:
Choose and pick your cherries. You will need about 4 cups of finely chopped and pitted cherries. As with jam, the jelly should only be made in small batches of about 4 cups at a time.
Start preparing your jars and lids, so you'll have them ready for later. A dishwasher on the sanitize cycle, or a hot water bath will work.
Wash the cherries in cold water and pit them using a cherry pitter or a knife. Make sure you remove any leaves and stems.
Finely chop or grind the cherries in a food processor, blender or juicer. Often 6 to 8 cups of cherries will yield 4 cups of juice. If needed, you can add water to make up the difference.
Place the cherries on the stove in a large pot over medium to high heat, stirring enough to prevent burning. Once it starts to boil, reduce the heat and allow to simmer for 10 minutes. If you used a juicer in step four you could skip to step seven, otherwise, continue.
Place the cooked cherries through a jelly strainer or through a cheesecloth in a colander. Sometimes jelly can form crystals. These don't affect taste and aren't harmful, but if you don't want them, then you should let the juice stand in a cool place overnight and straight through two thicknesses of damp cheesecloth to remove crystals.
Mix the pectin with 1/4 cup of sugar or sweetener. If you aren't using sugar, then you'll need to stir vigorously to prevent clumping of the pectin. Place the mix in a big pot over medium to high heat, stirring enough to prevent burning. It will take about 5 to 10 minutes to reach a full boil.
Once the mix has reached a full boil, add the rest of the sugar and boil for 1 minute. If you bring it to a boil slowly, then it will reduce foaming.
Skim any excess foam off the top.
Test for thickness using a metal tablespoon sitting in a glass of ice water. Scoop a half spoonful of mix and allow it to come to room temperature. If it thickens to a consistency you like, then the jelly is done. If not you can add more pectin and bring to a boil for one minute.
Allow it to stand for five minutes and stir completely if you want to prevent the fruit from floating to the top.
Fill jars 1/4 inch from the top and seal. Follow canning instructions.
Jelly is good for 12 months in storage. After 6 to 8 months it can get darker in color and runny. Although still safe to eat, it is best to consume within 6 months.