Here's what I did:
I cleaned about 1500 grams of rhubarb and cut it into little 3 cm pieces.
I peeled the skin of 5 grapefruits with a potato peeler. After that I squeezed out all the juice. My grapefruits weren't heavyweights though. I got about 400 ml of juice.
On a low fire I heated up the juice with the painstakingly finely chopped peels and about 3 inches of grated ginger. I added 1000 grams of gelling sugar. This is a sugar with pectin in it. You need this pectin to get the jam to set.
When the juice mixture got to a boil I added all the rhubarb and let it boil quite vigorously for about fifteen to twenty minutes.
At this point you need to check if the jam has set. There are a gazillion ways to do this, with plates in freezers and god knows what. Here's what I do: I take a spoon, put a little bit of the jam on the spoon and stick it in the fridge for 5 minutes. If the jam has gotten a jam like consistancy it has set. (Hurray!). If it doesn't, boil for a little longer, or if it doesn't set at all, you might need more of the pectin sugar.
I sterilized jars, put the jam in a measuring cup with a spout and used that to pour it in the jars. With a potholder (those jars get hot!!!!!) I screwed the jars shut and put them upside down to cool. This way you get a more secure vacuum and the jam will keep better.
The end result is a lovely tangy jam or confiture or whatever you want to call it. Slightly bitter, but that is how I like it!
Today I bought 2 kilos of nectarines and I think I'm going to do a nectarine, orange, cardemom (or vanilla) jam with that. The only problem: I ran out of jars! I checked to local stores, but they charge €1,50 for a very ugly empty jar. So, Mum to the rescue: she is bringing jars when she comes over this Sunday. I doubt that this will be the end of jamming season, so if you have any jars with metal lids to spare, AND you are close, please let me know!