Add juice and pectin to a pot and bring to a rolling boil, one that can not be stirred down. After it comes to a boil add sugar and butter (this keeps it from foaming up as much.) Allow to come back up to a boil and boil for 1 minute.
To make sure your jelly will be the right consistency, keep a spoon in ice water while preparing the jelly. When you are ready to test just shake the water off of the spoon and dip out about half a spoon full of jelly. Allow to cool for a few minutes. If it sets up on the spoon you should be good to go.
Can/ Preserve using desired method or refrigerate for immediate use.
The yield for 1/2 gallon should be around 9 cups.