Jam is done when:
- a blob forms a film after a short period of time on a cold plate and stops running
- you can cut through a small blob of jam on cold plate and it stays divided
- you can see the bottom of the pan when you cut through the jam with a spoon (seems to be the most reliable!).
For rhubarb:
- 1kg rhubarb in pieces
- 400g sugar
- 1/2 lemon (zest, juice, seeds)
Mix the rhubarb lemon juice, zest, and spent lemon half (with seeds!) and let sit for 1+ hours (the juices come out of the rhubarb). I think the lemon seeds have pectin (?) so they matter.
Bring to a boil, while stirring, and simmer for a total of 30-45min (until it’s jam, it does set more when it cools down, about 40min is right). Take the lemon and seeds out, obviously.
You can boil some jars and their lids in water to sterilize them while you make the jam…
Strawberry:
- 1kg strawberries cut in medium small pieces
- 200g sugar (20%)
- 1 tbsp fresh lemon juice
Let the strawberries sit in the sugar and lemon juice for an hour. Bring to a boil, and keep on a barely simmering for 30min. Then bring to a boil for 10min, then put in a jar.
Raspberry:
- 1kg raspberries
- 500g sugar (50%)
- 1 tbsp fresh lemon juice
Let the raspberries sit in the sugar and lemon juice for an hour. Bring to a boil, and keep simmering medium high until thick enough ( about 25-30min, little liquid left). At the beginning, when it first boils, skim off the white foam and a couple of tablespoons worth of the seeds.
Blackberry (overnight!):
- 1kg blackberries
- 600g sugar (60%)
- 2 tbsp fresh lemon juice
Let the blackberries sit in the sugar and lemon juice overnight. Bring to a boil, and keep on a simmering until thick ( about 30min).
Apricots (fast)
- 1kg apricots
- 800g sugar
Dice apricots, mix with sugar, let sit for ~30min, bring to a boil and reduce until jam. About 15min or less, much faster than other fruits.