*Use firm, ripe berries for the best flavor and set. (You don't want to use overripe berries or the jam may be too soft and runny.)
Wash and rinse glass or plastic containers. How many you use depends on how big they are. This recipe makes about 7-8 cups of jam.
Add berries to a large bowl and lightly mash them. Be careful not to over mash them---hey should still look fairly chunky, but not like whole berries.
Measure out exactly 3 cups of mashed berries and pour them into a separate large bowl. (If you have leftover mashed berries you could freeze them for smoothies or use them for topping on pancakes or waffles.)
Gradually stir in 1 cup of the sugar to the mashed berries, and stir until sugar is dissolved. Repeat, adding just one cup of sugar at a time and then mixing, until you use up the remaining 4 1/4 cups of sugar.Let stand for 10 minutes.
In a small saucepan, stir together pectin with 3/4 cup water. Bring to a rolling boil (a boil that doesn't stop when stirred) over medium-high heat, stirring often. Boil for one minute, stirring constantly. Remove from heat.
Stir pectin into the berries mixture. Continue stirring the mixture until sugar is completely dissolved and no longer grainy. This step is important! (see notes in post above).
Pour jam into containers, leaving 1/2in of space at the top of the container, for expansion. Cover with lid and allow jam to rest at room temperature for 24 hours before freezing.
Jam will keep for up to 3 weeks in the refrigerator, or freeze for up to one year.