One recipe for white grape jam requires 3 1/2 pounds of white grapes, low-sugar pectin, sugar, water, and a food processor. To can the jam, you will need jars, lids, rings, and a canner.
First, wash off the grapes, and then measure out 9 1/2 cups. Chop the grapes in the food processor until they are all mashed, but there is still some stiffness to the mixture. Put the canner on, and wash the jars, lids and rings. Place the jars in the oven at 350 F for 10 minutes to sterilize them, and then reduce the heat to 200 F.
Put the lids and rings into a small pot containing water. Bring the water to a boil to sterilize the lids and rings, and then keep the heat on low. Place the grapes into another pot, add 2 1/3 cups of water, and simmer the mixture for 10 minutes. Add 8 tablespoons of pectin to the mix slowly, stirring throughout. Then, bring the mixture to a boil that you cannot stir down, add in 3 1/4 cups of sugar, and let the mixture boil for another minute.
Turn off the heat and ladle the jam into the jars, leaving at least a quarter inch free at the top. Remove the air bubbles from the jars, and wipe off the rims to ensure a good seal. Put the lids on the jars, put the rings on them, and tighten them as far as they will go without forcing them. Place all the jars in the canner, and boil them for 10 minutes, adjusting for altitude. Finally, let the jars sit for five minutes with the heat off, and then remove them and allow them to cool another eight hours before removing the rings.