Method:
Measure prepared fruit into heavy saucepan. Add Certo crystals and stir well. Place over high heat, stir until mixture comes to a full boil. Stir in sugar. Continue to stir over high heat until mixture comes to a full rolling boil. Boil hard for 1 minute, stirring constantly. Use the “sheeting-off test” and cool a small amount to room temperature to determine when the jam stage is reached. (Continue boiling if needed). Remove from heat. Stir and skim foam for 5 minutes to prevent floating fruit. Pour into sterilized jars and seal.