First, you need six cups of ripe berries. Sort out the bad ones and pick off any stems,
Pour into a colander and rinse well.
Pour rinsed berries into a pot (I used an 8 qt, but anything bigger than a 3 qt should work).
With a potato masher, mash berries well.
Add two tablespoons lemon juice, and one package of pectin to the mashed berries.
Then add 5 cups of sugar.
Stir well until all sugar is dissolved. Return to a rolling boil, stirring almost constantly.
Meanwhile, have your clean jars--half-pints for jelly/jam--heating in a sink of very hot water.
When the berries are at a full boil that you can't stir down,
Skim the foam (if any) from the berries.
Don't throw this foam out, though! Put it into a small dish as it is completely edible and makes a tasty spread on a piece of toast; a preview of what your finished jam is going to taste like.
Then ladle into the hot half-pint jars, leaving 1/4 inch head space.
Wipe the rims with a clean wet cloth, place on lids and screw down with bands.
Put into a rack suspended in a boiling water bath canner
When rack is full, lower into the bottom of the canner. The jars should be covered by 1-2 inches of water. If there is not enough water to cover jars by one inch, add some from your hot water in sink that was used to heat the jars prior to filling.
Put lid on the canner, and return to a full boil. Boil for 15 minutes, then remove jars and place on a dry towel in a location free from drafts.
Don't touch for at least twelve hours. As the jars cool, you will hear the lids seal with a pop. Do not touch them to check for seal until fully cooled--after 12 hours!--or you might get a false seal.
And there you have it, blueberry jam! Easy and delicious.