Directions

1. 1

   Rinse the fresh blueberries thoroughly under cool running water and drain well. Sort through them gently, removing any stems or damaged berries. Measure out 3 pounds 8 ounces of sorted berries.

2. 2

   Place the blueberries in a large, heavy-bottomed pot (at least 8 quarts capacity). Using a potato masher or the back of a wooden spoon, gently crush the berries to release their juices. Work in batches if needed, mashing until about half the berries are broken down while leaving some whole berries intact.

3. 3

   Measure 1 pound 12 ounces of sugar and add it to the crushed blueberries in the pot. Stir well to combine, ensuring all the sugar is distributed throughout the berries.

4. 4

   Squeeze fresh lemons to obtain 1/4 cup of juice, straining out seeds and pulp. Add the strained lemon juice to the berry-sugar mixture and stir to combine thoroughly.

5. 5

   Place the pot over medium-high heat. Bring the mixture to a rolling boil, stirring frequently to help dissolve the sugar and prevent sticking. Once boiling, reduce the heat to medium and continue cooking uncovered.

6. 6

   Maintain a steady, vigorous simmer for 30 to 45 minutes, stirring occasionally, until the jam thickens. Test for doneness by placing a small spoonful of hot jam on a chilled plate; it should wrinkle slightly when pushed with your finger and hold its shape. The mixture should reach 220°F on a candy thermometer.

7. 7

   Remove the pot from heat. Skim off any foam from the surface using a clean spoon. Let the jam cool for 5 minutes, then transfer to sterilized jars, leaving 1/4 inch headspace. Seal according to standard canning procedures, or refrigerate in airtight containers for up to 3 weeks.