Old-fashioned, water-bath-canned grape jelly you can make with your own strained juice or good store-bought juice.
Jelly keeps setting as it cools, so do not judge it while it is hot.
Always use bottled lemon juice for consistent acidity. Do not double or combine batches. Label your jars with the date.
Sealed jars keep up to a year in a cool, dark place. Once opened, refrigerate and use within 3 to 4 weeks.