Until Strawberry Season!
Follow the recipe. Do not reduce sugar or use sugar substitutes. The exact amount of sugar, fruit and pectin is necessary for a good set. Do not double recipes; mixture may not set.
Use fully-ripened fruit and fruit juice at room temperature to help sugar dissolve. Crush berries one cup at a time; a potato masher works well. If using a food processor, pulse (on/off) to chop fruit – do not puree!
You can use unsweetened frozen fruit. Thaw the fruit to room temperature and crush to equal the same amount of crushed fresh fruit.
For freezer jam, use clean plastic containers with tight-fitting lids that have been rinsed with boiling water.