Long before grocery stores provided the convenience of fresh produce in midwinter, settlers preserved fruit and even vegetables in preserves, jellies, fruit butters, jam and marmalades. Preserved fruit products such as these are made by mixing fruit with sugar and a thickening agent. Jam is specifically made by pulping fruit before adding sugar and thickening agents such as pectin. This differs from jelly, which is made of fruit juice, preserves, made from whole fruit, marmalade, made exclusively from citrus, or fruit butters, which have a sauce-like consistency.
Harvest wild blackberries from wild blackberry brambles. You can find wild blackberries growing along roadsides throughout the countryside all across the United States.
Wash wild blackberries in a sink, and pick out leaves, twigs and debris.
Wash your fruit jars in a dishwasher to sterilize them.
Sterilize the lid rings and lid tops with seals by boiling them in a small saucepan.
Crush the berries, and add them to a large saucepan. Add 1/4 cup of water.
Bring the berry mixture to a boil. Cover and cook for five minutes.
Force the mixture through a food mill to remove the blackberry seeds.
Add water to the berry pulp until you have 3 cups of mixture. The amount of water that you add will vary among batches of jam that you make.
Add sugar and berry mixture in an 8 quart stock pot. Mix well, and bring to a rolling boil. Boil for one minute, stirring constantly.
Remove the stock pot from heat and stir in pectin. Skim pulp and any remaining seeds from the surface using the wooden spoon.
Place a canning funnel into a canning jar. Pour the jam mixture into the canning jar through the funnel. Repeat this process with each canning jar.
Fill the canning pot with water. Place the canning lids onto the jars so that the seals come into contact with the jar mouths. Place the canning rings onto the jars and screw them loosely into place.
Put each jar into the canning pot. Bring the water in the pot to a boil to seal the lids onto the jars. Boil for approximately 15 minutes to seal the lids to the jars. Remove each jar from the water using a jar gripper. Place the jar on a counter to dry. The lid will seal to the jar as it dries.