Wash jars, bands and lids, in the dishwasher with the sanitize cycle, or by hand with hot soapy water. Set aside.
Remove stems of strawberries and slice up. Use a potato masher to mash strawberries. Add pectin and stir.
Add jars to stock pot with water completely covering with water. Bring to boil and keep hot until use.
Add strawberry and pectin mixture to dutch oven on stove over medium-high heat. Bring to boil and add sugar and butter. Stir constantly for five minutes.
As jelly boils, skim off foam.
Remove jars from water one-by-one and fill jars with strawberry mixture leaving a quarter-inch of space in the top of the jar. Place rubber lids and metal rings on jars. Fill all the jars, then return to the boiling water, and place the lid on the stock pot. Make sure there is at least one inch of water above jars.
Boiling time varies based on elevation where you live: 0-1,000 feet above sea level: boil ten minutes, 1,001-3,000 feet above sea level: boil 15 minutes, 3,001-6,000 feet above sea level: boil 20 minutes, 6,001-8,000 feet above sea level: boil 25 minutes, 8,000+ feet above sea level: boil 30 minutes.
Turn off burner and remove jars from water with canning jar lifter/grabber and place on cookie rack or towel to cool. Listen for jars to pop (seal).
If jars do not seal, place in refrigerator and use in next two weeks. Shelf life of this recipe is up to 18 months if sealed.