Wash and hull strawberries. Using a potato masher, mash strawberries leaving small chunks. .
Measure 5 cups of crushed strawberries into a saucepan. Add lemon juice and balsamic vinegar to crushed strawberries in same saucepan. Whisk in pectin until dissolved. Bring to a full rolling boil; stir frequently.
Add sugar all at once and stir constantly, return to a full boil that cannot be stirred down. Boil hard, stirring constantly, for 1 minute. Remove from heat and skim off foam, if necessary.
Fill prepared warm jars to 1/4 inch headspace. Wipe rims with a clean damp cloth or paper toweling. Place lid and band on jars, adjusting to finger-tip tight.
Place jars in canner and bring to full rolling boil over high heat. Once boiling, set timer for 10 minutes. After processing, turn off heat and remove canner lid. Remove jars and place on towel to cool. Allow to sit without touching for 24 hours. Check for seal, remove bands, wipe off jars if necessary, label and store in a cool, dry, dark place.