A friend of ours gave us 6 raspberry transplants from his garden and they spread quickly. We now have a pretty dense patch about 4' x 8' that produces a ton of fruit. Well, if the Japanese beetles don't get to them first. Hate those pests!
Even with the pests, I normally have enough strawberries to can a few dozen pints of this tasty sauce. I am not a fan of the seeds, so I run batches through my Nutri-Bullit which breaks down the seeds quite a bit.
When I first started searching for recipes for raspberry jam, all of them called for equal parts sugar and raspberries. Seriously? That seemed like a lot of sugar. And most recipes said that there isn't a need to use Pectin for thickening. That the raspberries already have enough. I'm not sure that's correct but I figure the less ingredients, the better.
Puree a batch of raspberries and measure out the juice. I use about 2/3 that amount in sugar, mix together in a pan and add in a splash of lemon juice just to give it a bit more tart. Bring to a boil and cook, stirring frequently, for about 5 minutes or until it starts to gel up a bit. (See note below.) Ladle into sterilized pint or 1/2 pint jars, wiping the edges of the top to make sure they're good and clean. Put on the lids and put into a canning bath for about 15 minutes. Remove from the bath and let the jars cool. The lids will "pop" as they cool.
To determine when the mixture will form a gel, use the spoon test: Dip a cool metal spoon into the hot fruit. Immediately lift it out and away from the steam and turn it horizontally. At the beginning of the cooking process, the liquid will drip off in light, syrupy drops. Try again a minute or two later — the drops will be heavier. The jam is done when the drops are very thick and two run together before falling off the spoon.
Since I use less sugar, my raspberries are more of a "sauce" than a jam. It's great on ice cream. Use equal amounts of sugar and raspberries if you want a thicker sauce.
Be sure to mark the date on the top of the jars before storing in a cool dark location. You'll want to use within a couple of years. Refrigerate jars after opening.