- 7 cups rhubarb, chopped
- 7 cups strawberries, sliced
- 9 cups white sugar
- ½ cup lemon juice
- Large pot or canning kettle
- Six 8 ounce canning jars with lids and rings
- Wooden spoon or tongs
- Wide-mouthed jar funnel
- Jar lifter
Mix rhubarb, strawberries, sugar and lemon juice in a large pot and let stand for at least 2 hours.
Bring the mixture to a boil over high heat, stirring frequently, then cook on medium-high at a gentle boil until a teaspoon of hot jam sets on a cold plate (see below), about 40-50 minutes.
Cold Plate Test for Jam
Put 3-4 small plates into the freezer when you start cooking the jam.
When you think the jam is almost ready, take one of the plates from the freezer and spoon some jam on the cold plate. Tip the plate to one side. If mixture is thin and just pours off the plate, it’s not ready yet. The jam should be thick and run slowly along the plate.
Preparing Jars and Lids
While the jam is cooking, prepare your jars and lids. To do so, fill a large pot or canning kettle with enough water to fully immerse your jars in 1 inch of water.
Bring jars to a boil, then reduce to medium, keeping everything at a nice gentle boil while you wait for the jam to finish cooking.
Pre-heating the lids and rings is not necessary.
When the jam is ready, skim of any remaining foam, then remove the jars from the hot water by inserting a wooden spoon or tongs into the jars then tipping the water out as you lift the jars out of the pot.
Place an open-mouthed jar funnel into the top of the jar, then pour the jam into the jar through the funnel, leaving a ¼’ of space at the top of each jar for expansion. If you spill jam on the rim of the jar, wipe it clean with a damp paper towel – not a kitchen cloth as it may not be sterile.
Put a lid on the jar and tighten it (not too tight), then put the jar back into the hot water using the jar lifters.
Continue with the rest of the jars until all the jam is done, then boil the jars for 5 minutes. Make sure the water covers the jars by 1 to 2 inches during processing.
Remove jars from hot water with the jar lifters and set on a tea towel to cool. You will hear cheerful popping sounds as the jars cool down- this is normal and means that the jars are properly sealed.
Enjoy your beautiful jam on freshly baked homemade bread, baguette or croissants.