Place 9 pints fresh blackberries into a heavy-bottomed pot with 1 cup of water.

Bring the mixture to a boil over medium-high heat, mashing as the mixture cooks.

After about 5 minutes, the blackberries should have completely fallen apart and released their juices. Remove the mixture from heat.

Pour the blackberry pulp through a jelly bag, or a cheesecloth-lined strainer. Allow the mixture to drain for at least an hour until it stops dripping and the pulp is pretty dry.

Measure the collected juice, you should have about 4 cups. (Other yields will work fine too, see notes.)

For every cup of blackberry juice, add 3/4 cup of cane sugar.

Place the sugar/juice mixture into a deep jam pot and bring to a boil over high heat.

After about 5-8 minutes, the mixture should reach gel stage. Test for gel stage on a plate that's been placed in the freezer, or with an instant-read thermometer (220 degrees F at sea level, see notes for other elevations).

Pour the mixture into prepared jam jars, leaving 1/4 inch headspace.

Seal with 2 part lids.

Store in the refrigerator for immediate use, or freezer for up to 6 months. For longer-term storage, canning is a better option.

Prepare a water bath canner before you begin making the jelly (while the juice is straining).

Fill jars the hot jelly mixture, leaving 1/4 inch headspace, and seal with 2 part lids.

Process in a water bath canner for 10 minutes.

Remove the jars to cool on a towel on the counter. After 24 hours, check seals and store any unsealed jars in the refrigerator for immediate use.

Properly canned and sealed jars of homemade blackberry jelly will maintain quality for 12-18 months at room temperature in the pantry.