Cooked Grape Jelly

Wash jars and lids in hot soapy water, rinse and sterilize jars and lids by (1) boiling in water for 15 minutes (leave in water til needed.) Lids may be sterilized by placing in boiling water and boiling 5 minutes(leave in warm water til needed.) Utensils should also be sterilized. Stem fruit and thoroughly crush fully ripe grapes. Add water, bring to a boil and simmer, covered 10 minutes. To extract juice, place prepared in jelly bag and squeeze. NOTE: To make own jelly bag, use a square meter of cheesecloth, 3 layers thick. Wet cloth and spread over a colander or strainer in a bowl. Add fruit. Bring corners of cloth together. Twist bag or cloth and squeeze to extract juice. For clearer jelly, use 1 1/2 times fruit called for and let juice drip through without squeezing. Using liquid measure, measue the amount of prepared juice and add to a large 4 to 8 qt pan. Add lemon juice if listed. Measure sugar. DO NOT REDUCE SUGAR. Add the exact amount of sugar specified and mix well. Place pan over high heat; bring to a boil. At once stir in Certo liquid. Bring to a full rolling boil and boil hard for 1 minute, stirring constantly. Remove from heat. Skim off foam with a metal spoon. Stir and skim for 5 minutes. Pour quickly into prepared jars leaving 1/4 inch head room. Seal jam at once with 2 piece metal lids or paraffin wax.