In a large stainless steel saucepan, combine grapes and 2 cups of water.
Bring to a boil over medium-high heat, stirring frequently.
Reduce heat to low. Use a potato masher to crush the grapes, and continue cooking for 2-3 minutes.
Line a sieve or strainer with a couple of layers of dampened cheesecloth, set over a deep bowl.
Pour the grape mixture into the cheesecloth-lined strainer and allow it to sit for about 2 hours for the juice to extract.
You should end up with four cups of clear grape juice. If you don't get the required four cups, add a half cup of boiling water to your strainer.
In a large, deep stainless steel saucepan, combine grape juice and sugar.
Over high heat, stirring constantly, bring to a full rolling boil.
Stir in pectin. Boil hard for one minute. Remove from heat and skim off any foam.
Quickly pour jelly into sterilized jars, (eight 8 ounce jars) wiping the rims with a damp paper towel. Center lids on jars and secure rims to finger tight.
Place jars in a boiling water canner for ten minutes.
Remove jars, allow to cool, ensuring they are sealed, and store.
Notes
2 hours of the prep time indicated include allowing the juice to strain out of the grapes while you do other things. Processing time is included in the cooking time.
Check your Pectin Pectin has an expiry date and if you use expired pectin, there's a good chance that your jelly won't set.
Follow the Recipe Many recipes are forgiving and you can put your own spin on them. Jellies and Jams are not those recipes. Many factors come into play and the recipe should be followed exactly.
Don't Press or Squeeze When the juice is extracting from the fruit, patience is required. Never press or squeeze the fruit. This will result in cloudy jelly. We want it sparkling clear!
Have Everything You Need clean and ready before beginning. Cut the opening of the pectin pouch and stand it up in a glass so that it's ready at hand.
Use a Timer Boiling time, and processing time is everything here, so don't rely on the clock. Set your oven timer, phone timer or Google/Siri assistant.
Inspect your Jars Canning jars are reusable, but check both new and used jars for cracks or chips. If there are any chips on the rims, the jars will not seal.
Lids aren't Reusable Although the jars, as well as the screw bands are reusable, new lids must be used each time you make jelly, because they most likely won't form a seal the second time.
Fill Jars with a Funnel A canning funnel keeps spills to a minimum and keeps the jar rims clean.
Wipe the Rims Use a damp paper towel to wipe the rims of the filled jars before centering the lids on them. This will ensure they are clean and ready for a seal.
Leave Headspace Fill jars to a ¼" to ½" of the rim. Less than that and you will risk an improper seal. Too much headspace can result in discolouration of the jelly.
Be sure to read the FAQ section in the post for more jelly making tips.