Of course Doreen is right that you can make Concord jelly by boiling it
until it "sheets" on the spoon. Both my mother and mother-in-law did it
this way. But to make it work, you have to match sugar to juice, cup
for cup, you do have to boil it for a while, and you have to watch it
carefully. The result is better than you can buy in the supermarket,
but still a very sweet product. If you want to cut back the sugar for a
real fruity taste, try Pomona's. You can put it in the jars as soon as
it reaches a boil.