Grape Jelly

A liquid-pectin jelly from a Certo promotional booklet, written for cooks who already knew the standard bottle method. A few of its assumptions no longer hold.

• The sugar quantityThe printed figure is corrupt. A four-cup batch of bottled grape juice set with one bottle of liquid pectin took 7½ cups of sugar, roughly 3¼ lb, in the Certo booklets of the period. Treat the number on the page as unreliable and follow the ratio on your pectin package.
• A bottle of Certo is not what it wasThe old glass bottle held about 8 fl oz, hence the "scant cup." Certo is now sold in 3 fl oz foil pouches, two to a box. Two pouches come to 6 fl oz, so quantities do not transfer directly; go by the current package chart.
• Order of workWith liquid pectin the sugar goes into the juice first. Bring to a full rolling boil that cannot be stirred down, add the pectin all at once, return to the rolling boil for exactly one minute, then take it off the heat and skim.
• Do not test for a sheetWith a short-boil pectin jelly the timed one-minute boil is the test, not the sheet off a spoon or a thermometer reading at the 220F jelly point. Boiling well beyond the minute in the hope of seeing a set can degrade the pectin and spoil rather than improve the result.
• Bottled grape juiceThe recipe means plain unsweetened grape juice, not a sweetened grape drink or cocktail. Grape juice can throw tartrate crystals; where it does, chilling the bottle overnight and pouring the clear juice off the sediment is the old remedy, though most commercially bottled juice has already been treated against it.
• SealingThe booklet era sealed jelly glasses with melted paraffin. That is no longer recommended; the wax shrinks and admits mould. Use a current tested water-bath processing time for jelly, or simply refrigerate the jars and use them within a few weeks.