Prepare your water bath canner by filling it with water, and setting it on the stove. Turn the burner to high. Once it reaches a boil, reduce it to simmer. You want to keep the water hot so that everything is ready when the jam is.
Wash and sanitize your jars. You'll want to keep them warm to avoid having them crack when placed in the canner. You can fill them with hot water, or place them on a tray in the oven at 200 degrees F.
Wash your lids and set aside in clean place.
Rinse the strawberries. Remove the tops and cut in halves or quarters (8 cups total). Place in a heavy-bottomed saucepan.
Heat the fruit over medium heat until the juices start to bubble. At this point, you can mash the fruit with a potato masher, or use an immersion blender. Pro tip: blend about 30% of the strawberries, and just gently pulse the others, leaving some chunks. The goal isn't to puree the fruit totally as that will impact the final texture of the jam.
In a small mason jar, combine 1/2 tsp calcium powder with 1/2 cup cool water.
In a separate bowl, combine sugar (1.5 cups) and pectin (2.5 tsp). Set aside. To prevent clumping in the fruit, Pomona's must be mixed with your sweetener before being added to the fruit.
Add the lemon juice (1/4 cup) and calcium water (2.5 tsp) to the pot with the strawberries, stir. Add the sugar/pectin mixture, and bring to a rolling boil. Stir constantly for 3 minutes, turning down the burner to medium if the jam starts popping. Pro tip: actually set a timer and stir for the full three minutes. The constant stirring prevents the jam from burning, and the cook time is important to help the jam set.
At this point, turn the burner under the canner back up to high and get that water boiling again.
Remove the jam pot from heat, and stir gently for 5 more minutes. At the end of the 5 minutes, remove any foam that remains.
Using the funnel and a ladle, add the jam to your prepared jars, leaving 1/4 inch of headspace at the top. Headspace is the amount of room between the top of the food, and the rim of the jar.
Using a wet clean rag, wipe the rim to make sure there isn't any sticky jam on there. Place a clean lid on the jar and then a ring. Tighten the ring to fingertip tight (tight enough that it won’t come off, but not so tight that a normal person couldn’t budge it).
Using canning tongs, add your jars to the boiling water, and put the canner lid on. Pro tip: you must have at least 1 inch of water over the tops of the jars for safe canning. Process (boil) for 10 minutes.
Remove the canner from heat, and let sit for 5 minutes. Remove the jars and place them on towels on the counter. Make sure you place them someplace where they can be undisturbed for 12-24 hours.
After everything has cooled, check the seal by pushing down on the middle of the lid. If it doesn't give way, it's sealed. If the lid bows a little bit, put that in the fridge and use it within 3 weeks.
Label the sealed jars, and store in a cool dark place for up to a year.
Makes 5, 8 oz jars.8 cups fresh strawberries generally equal about 5 cups of mashed berries.Will last for 1 month in the fridge or 12 months sealed and at room temperature.