Crush berries. Add crushed fruit into sieve or cheesecloth and let hang and drip into bowl until dripping stops. Press gently. Measure exact amount of juice into large pot. If necessary, add up to 1/2 cup water to get exact amount of juice needed. Stir sugar into juice. Add 1/2 teas. butter or margarine to reduce foaming, if desired. Bring mixture to a full rolling boil on high heat, stirring constantly. Stir in pectin quickly. Return to a full boil and boil for exactly 1 minute, stirring constantly. Remove from heat. Skim off any foam with metal spoon. Ladle quickly into prepared jars, filling within 1/8 inch of tops. Cover. Process jars on elevated rack in boiling water for 5 minutes. Water must cover jars by 1-2 inches. Remove jars from water and cool. Let stand at room temperature for 24 hours. Store in cool, dry, dark place for up to 1 year. Refrigerate opened jellies for up to 3 weeks.