You can create grape jelly quickly by combining the correct amounts of white sugar, grape juice and powdered fruit pectin. Also, you can use real grapes, juice sugar with added pectin and lemon.
The first method involves using grape juice instead of grapes.To begin, simmer 4 cups of 100 percent grape juice over medium-high in a large saucepan. Whisk in 1 tablespoon powdered pectin and continue whisking occasionally for 3 minutes. Lower heat to medium-low then add 2 cups of sugar, whisking until dissolved for about 5 minutes.Let the liquid cool slightly before pouring into jars and refrigerating.
The second method involves actual grapes. Tip the 2 pounds of grapes into a large saucepan set over a low heat, then cover and leave to gently cook for 5 minutes until the juices start to run. Take a potato masher or fork and mash up the grapes. Leave to cook for about 10 minutes more, mashing every now and again until the grapes are falling apart.
Place a clean towel in a sieve set over a bowl, then pour the grape mixture into this. Let the mixture drip through for at least 1 hr or preferably overnight. Measure out 2 1/2 cups of juice and pour it into a pan along with 1 pound sugar and lemon juice. Bring to a boil over high heat. Skimming any scum as it boils, let the mixture bubble until the temperature reaches 221 degrees Fahrenheit. Pour the hot jam into a sterilized jar.