Prepare a water-bath canning pot and two 8-oz jam jars (or 4 4-oz jars). Place a small saucer in the freezer.
Combine the red currant juice and sugar in a large, wide saucepan and bring the mixture to a boil, stirring to dissolve the sugar.
Turn heat down to medium and boil the mixture until it reaches 220 degrees, stirring frequently to prevent scorching and skimming off any foam or skin that accumulates. (This happened relatively quickly for me and the mixture still seemed quite liquid. You can also test whether the mixture has reached the gelling point by placing a small amount on the chilled saucer, returning the saucer to the freezer for one minute and then examining the jelly. If it seems set and wrinkles when pushed with your finger, it is ready. )
Remove the saucepan with the jelly from the heat and skim off any foam or impurities.
Ladle the jelly into the prepared jars, leaving ¼ inch headspace. Bubble the jars and wipe down the rims.
Process the jars in a boiling water bath for ten minutes. Allow to cool five minutes before removing the jars from the water bath.
Cool jars on a counter. Check the seals and store in a cool, dark place for up to one year.
Recipe by West of the Loop at https://www.westoftheloop.com/2014/07/30/farmers-market-find-red-currants/