Rinse, then hull strawberries. Put them into a pot over very gentle heat. Press the berries against the sides of the pot with a wooden spoon to extract the juice. They should be soft in about 10 to 15 minutes. Add the sugar slowly and stir until it is dissolved. Bring the jam to a fast rolling boil and boil it for exactly 10 minutes, stirring frequently. Let the jam stand for about 5 minutes, skim and stir so that the berries will be evenly dispersed through the jam, then pour into hot sterilized jars. Cover at once with 1/8 inch hot paraffin. Cool, then cover with tight lids. Makes about 6 pints.