Step 1: Prepare your canning equipment. Wash 8 (8-ounce) canning jars, lids, and bands in hot, soapy water. Rinse thoroughly. Keep jars hot in a simmering water bath canner, or in a dishwasher cycle, until ready to fill. Place lids in a small saucepan, cover with water, and bring to a simmer (do not boil) to soften the sealing compound. Keep warm.
Step 2: Hull and crush the strawberries. Wash fresh, ripe strawberries thoroughly. Remove the green caps (hull) from the strawberries. Crush the strawberries using a potato masher or an immersion blender until you have 4 cups of crushed fruit. For best results, use firm, ripe berries.
Step 3: Combine strawberries and pectin. In a large, heavy-bottomed pot (at least 6-8 quart capacity) or Dutch oven, combine the 4 cups of crushed strawberries and the entire box of powdered pectin. Stir well to combine.
Step 4: Bring to a rolling boil. Place the pot over high heat and stir constantly until the mixture comes to a full, rolling boil that cannot be stirred down. This is crucial for activating the pectin.
Step 5: Add sugar and boil again. Once a rolling boil is reached, immediately add all 7 cups of granulated sugar. Stir constantly until the sugar is completely dissolved. Bring the mixture back to a full, rolling boil that cannot be stirred down. Boil hard for exactly 1 minute, stirring constantly. This ensures proper gelling and prevents scorching.
Step 6: Remove from heat and skim foam. After 1 minute of hard boiling, remove the pot from the heat. Skim off any foam that has formed on the surface using a spoon or ladle. This will ensure clear, appealing jam.
Step 7: Ladle jam into hot jars. Carefully ladle the hot jam into the prepared hot jars using a canning funnel, leaving 1/4 inch of headspace from the rim of the jar. Wipe the rims of the jars clean with a damp paper towel to ensure a good seal. Any jam on the rim can prevent sealing.
Step 8: Place lids and bands. Center a warm lid on each jar. Screw on the bands just until fingertip-tight; do not overtighten. Place the filled jars into the canning rack and lower them into the preheated water bath canner, ensuring jars are fully submerged by at least 1-2 inches of water.
Step 9: Process jars. Bring the water to a full, rolling boil. Once boiling, process the jars for 10 minutes. Adjust processing time for altitude if necessary (add 1 minute for every 1,000 feet above sea level).
Step 10: Cool and check seals. After processing, turn off the heat, remove the canner lid, and let the jars sit in the hot water for 5 minutes. Carefully remove the jars from the canner using a jar lifter and place them on a clean towel on your countertop, ensuring they are not touching each other. Let them cool undisturbed for 12-24 hours. You will hear the satisfying 'pop' as the lids seal. Once completely cool, check the seals by pressing the center of each lid. If the lid does not flex, it is sealed. Remove the bands, wipe down the jars, label, and store in a cool, dark place. Any unsealed jars should be refrigerated and consumed within 3 weeks. For long-term storage, consider using reliable Basics Glass Food Storage jars.