Pick over raspberries and discard any spoiled or under ripe fruit.

Mash the raspberries and measure the result. For every cup of mashed fruit, add 1 cup of sugar.

Place the sugar and fruit in a jam pot. Bring to a hard boil over medium-high heat, stirring continuously to prevent scorching.

After 8 to 12 minutes the raspberry jam should reach gel stage. The setpoint can be tested on a plate that's been placed in the freezer, or you can use an instant-read thermometer. The jam should be finished when it reaches 220 degrees F (or 104C). Do not overcook!

Once the jam reaches the setpoint, remove the saucepan from the heat and ladle the jam into prepared jars.

If canning, process the jars in a water bath canner for 10 minutes (or 15 minutes above 6,000 feet in elevation). Remove from the canner and allow to cool on a towel on the counter for 12-24 hours. Check seals and store any unsealed jars in the refrigerator for immediate use.

Caning is optional, and this jam will keep for several weeks in the refrigerator or up to 6 months in the freezer. Properly canned and sealed, the raspberry jam should maintain peak quality on the pantry shelf for 12-18 months. Refrigerate after opening.