Cooked Blueberry Jam - CERTO Crystals

Crush blueberries, one layer at a time. Measure exactly 4 cups prepared blueberries into large saucepan. Stir in lemon juice. Add pectin crystals; mix well.

Bring to full rolling boil on high heat, stirring constantly. Add sugar; mix well. Return to full rolling boil; cook 1 min., stirring constantly. Remove from heat. Stir and skim foam for 5 min. to prevent fruit from floating to surface.

Pour immediately into warm sterilized jars, filling to within 1/4 inch of rims. Cover with lids. Let stand at room temperature 24 hours or until set.