Strawberry Rhubarb Jam is a classic combination - and delicious on everything from plain buttered toast to spread across a scrumptious muffin. This recipe does not use pectin.
Add sugar and continue stirring occasionally, until jam has thickened - about 10-15 minutes (see note for how to test jam for doneness). Skim off any foam that's formed on the surface and discard.
Process the jars in a hot water bath (see note below). I usually do this by filling my largest pot with enough water to cover the tops of the jars and bringing it to a rapid boil. Place the jars into the boiling water (using tongs or a jar lifter) and let them sit in the bath for 10-15 minutes - the lids will "pop" inwards, which signifies the lids have vacuum-sealed. (The lids may not pop until after you remove the jars from the water bath.)
Remove jars from the water bath and let cool. Any lids that don't dip down in the middle, or that spring back, have not sealed. Place those jars in the refrigerator and enjoy them first.
All other sealed jars may be stored in a dark, dry place for up to one year.