Step 1

Remove stems and crush berries before measuring the 4 cups.Boil jars on rack in large pot filled with water 10 minutes.

Step 2

Place flat lids in saucepan with water. Bring to boil; remove from heat.

Step 3

Let stand in hot water until ready to fill.

Step 4

Drain well.In 8 quart pot combine crushed blueberries and lemon juice.Measure sugar in separate bowl. (Scrape extra sugar from cup with spatula to level for exact measure.)

Step 5

Add fruit pectin and butter to fruit. Bring mixture to full rolling boil over high heat, stirring constantly.Quickly add sugar to fruit mixture. Bring to full rolling boil and boil 1 minute, stirring constantly.

Step 6

Remove from heat. Skim off any foam.Fill all jars quickly to 1/8" of tops. Wipe jar rims. Cover quickly with flat lids. Screw bands tightly.Invert jars for 5 minutes, then turn upright. After 1 hour check seals.Or use water bath method.Makes 5 Cups