Concord Grape Jelly

Concord Grape Jelly:
*6 cups bottled juice, without sugar added or reconstituted from frozen, without sugar. I used Welches Concord Grape.
*Pectin – 2 boxes OR 12 tbs of regular bulk pectin OR 6 tbs low or no sugar needed pectin in bulk.
*Sugar – About 4.5 cups of dry, granulated (table) sugar, if you use the no-sugar-needed pectin or low sugar pectin. If you use regular pectin, you’ll need 7 cups of sugar.
*1 tbs butter (reduces foaming)