Rhubarb Strawberry Jam
500 g/ about 1 pound strawberries, weighed after cleaning
1 kg/ about 2 pounds rhubarb, weighed after cleaning and peeling
2 organic lemons
1,5 kg/ about 3 pounds granulated sugar
Wash and hull the strawberries and clean and peel the rhubarb. Halve the strawberries and cut the rhubarb into small pieces.
Grate the zest of one lemon and juice both of them. Grate the apple as well.
Place all the ingredients in a large pan, bring to a boil while stirring often and let cook for about 50-60 minutes until the jam starts to thicken. There will be quite a lot of foam forming during this time, make sure you remove that properly, it is not nice to have it in your jam, and I read somewhere that the jam will not keep that long if you haven't removed the foam before pouring the jam into the jars.
The cooking time is not an exact science, I am afraid. It depends a lot on how much jam you are making, on how big your pot is and how much pectin the fruit contains. You could already start checking after 30 minutes or so. I normally have an eye for it, I scoop some juice on a spoon and check how the drops are falling down from it, if that happens quickly the jam needs more time, if the drops take a moment to form, kind of come together, fall down slowly and seem to be thick enough than I stop the cooking process. This method is maybe not very appropriate for an inexperienced eye (it doesn't always work for me either) so for better results you should try the following:
Place a small plate in the freezer at the beginning of the cooking time. Check the consistency of the jam by dropping a few drops of juice on the plate. Put the plate back in the freezer and check again after a couple of minutes (not too long). The jam drops should wrinkle when pushed with the finger. If they don't wrinkle, keep cooking and checking until you get them to wrinkle.
While the jam is cooking prepare the jars. There are a lot of instructions on the internet about the best way to do that, for example here: http://www.taste.com.au/how+to/articles/572/how+to+sterilise+jars+and+bottles
To tell you the truth I don't make myself so much work, I just pour boiling water into the jars, place the lid on and shake. Then I pour the water out of the jars and place the jars onto clean towels until ready to use. If you follow my method is at your own risk. Just read other sources and decide what you want to do.
Pour the jam into the prepared jars and seal tightly.