Start by rinsing the blackberries in a large colander.
Place them in a large pot, a casserole dish (cast iron) or a jam pan.Add the sugar and mix.Let stand covered for 2 hours or even overnight. Then heat, stirring regularly and cook for about 30 minutes.Remove the scum using a slotted spoon. During cooking, wash and sterilize your jars by heating them in boiling water.
Then place a large sieve over another pot.Gradually pour the jam into the skimmer and stir with a wooden spoon until the fruit is completely squeezed.Large, there will be no more juice and pulp from the blackberries, continue cooking for another 10 minutes. Once your jam is ready, pour into the jars, being careful not to burn yourself.Fill them about 1 centimeter from the edge.Close them and turn them over until they have cooled. Then keep for a few weeks/months in a dry place away from light.
