Start by preparing jars and getting water in the canner heating. You want the canner hot, but not boiling, when the jars are ready to be processed.See full water bath canning instructions here.
For a Hot Pack
Wash and core strawberries, removing stems and bruises.
Put strawberries in a large pot.
Crush strawberries with a potato masher to bring on some juice
Stir in sugar. Heat slowly, stirring constantly.
When sugar is dissolved, bring to a boil.
Boil rapidly, stirring constantly. If it foams up a lot, add ¼ tsp. butter.
When jam has reached gelling point, skim off foam.
Fill hot jar with hot jam, leaving 1/4” headspace.
Remove air bubbles, wipe rim clean, and place seal and ring. Place the jar in the warm canner. Proceed to fill all jars. Process according to the chart below.
Processing with a Water Bath CannerPlace the jar in the warm canner. Proceed to fill all jars placing them in the canner.When all the jars are filled, bring the water in the canner to a boil. When a boil is reached that is when you'll start your timing. Process for the length of time on the chart below. Adjust for your altitude. After your time is over, turn the heat off remove the lid and allow the canner to rest for about 5 minutes. Then bring your jars up out of the water. Allow them to rest for another 5 minutes. Then remove the jars and place them a few inches apart on a thick towel to cool completely. Leave them alone for about 12 hours. When they are cooled remove the metal bands, check the seals, label the jars and store them away! Processing Times for Water Bath Canner (Hot Pack)Altitude – Half Pints and Pints are Processed the Same 0-6,000 ft - 10 minutesAbove 6,000 ft - 15 minutes
Adapted from: The National Center for Home Food Preservation
Keyword Home Canning, strawberry jam, Waterbath Canning
Recipe can be found at SimplyCanning.com https://www.simplycanning.com/recipe-for-strawberry-jam/