Preparation Sterilize canning jars and lids. Crush strawberries lightly with a potato masher in a 7- to 9-qt. heavy nonreactive pot. Simmer, stirring occasionally, 10 minutes. Add sugar and lemon juice and simmer, stirring constantly, until sugar is dissolved, about 2 minutes. Bring to a full boil and cook, stirring frequently (be careful not to let bottom scorch) and skimming off any foam. It's done when it becomes slightly thickened and a teaspoon of jam begins to gel when dropped on a chilled plate, after 10 to 20 minutes of boiling. Ladle hot jam into jars, filling to within 1/4 inch of top. Wipe rims with a dampened cloth and seal with lids. Put jars in a water-bath canner or on a rack set in a deep pot. Add enough hot water to cover jars by 2 inches and bring to a boil. Boil jars, covered, 15 minutes, and transfer with tongs to a rack. Cool completely and store in a cool, dark place.
Preparation Sterilize canning jars and lids. Crush strawberries lightly with a potato masher in a 7- to 9-qt. heavy nonreactive pot. Simmer, stirring occasionally, 10 minutes. Add sugar and lemon juice and simmer, stirring constantly, until sugar is dissolved, about 2 minutes. Bring to a full boil and cook, stirring frequently (be careful not to let bottom scorch) and skimming off any foam. It's done when it becomes slightly thickened and a teaspoon of jam begins to gel when dropped on a chilled plate, after 10 to 20 minutes of boiling. Ladle hot jam into jars, filling to within 1/4 inch of top. Wipe rims with a dampened cloth and seal with lids. Put jars in a water-bath canner or on a rack set in a deep pot. Add enough hot water to cover jars by 2 inches and bring to a boil. Boil jars, covered, 15 minutes, and transfer with tongs to a rack. Cool completely and store in a cool, dark place.