Begin by washing the fruit. Clean the rhubarb, dice - measure exactly four cups.
Clean the strawberries, remove the stems and mash the berries - measure exactly 2 cups.
Add the rhubarb and strawberries to a large heavy stockpot. Add the lemon juice.
Measure ¼ cup of sugar and mix it with the contents of the Sure-Jell. Sprinkle it into the fruit, mix well again and set it on the stove on high and bring to a boil, stirring constantly.
When it comes to a hard rolling boil (a boil you can't stir down) add the remaining sugar. Continue stirring constantly and return it to a boil. Boil for exactly one minute. (Set a timer to make sure you get it for a full minute).
Remove from the stove & immediately ladle into sterilized jars.
Using a clean damp cloth, wipe the tops of the jars to remove any jam that may have gotten on the top of the lids. (This will keep the jars from sealing.)
Place lids on jars, followed by the rings, screw it on tightly.
Process in a hot bath (boiling water) for 10 minutes to seal the jars.Makes 6 eight oz. jars.