Everbody wants to make strawberry jam and it is usually the first jam that they make when starting out. This is a shame because it is quite difficult to achieve a set and then disappointment can set in with the result that budding jam-makers are quite likely to give up before they've got going.
When I was a girl you could buy something called jam strawberries; Back then commercial strawberries were grown in open fields the dessert crop would be harvested and once there were no more large fruit to pick, the plants would be stripped of all of the smaller, perhaps mis-shapen, sometimes not-quite-ripe fruit and sold at a reduced price for jam. These fruit were actually perfect for the job as, unlike today's perfectly ripe commercial strawberries, they did not contain a high volume of water, which helped what little pectin the fruit contains to be more effective.
Today, if you want to have a go at the quintessentially 'cream tea preserve' then my advice would be to avoid supermarket strawberries if possible, and find a local Pick Your Own farm. There you can select the medium/smaller fruits which won't break down too much when cooked.
Will make approximately 1.3kg/3 lbs
900g/2lb small firm strawberries 900g/2lbs granulated sugar Juice of 1 large lemon
Place two small plates or saucers into the fridge or ice-making compartment if you have one.
Wash jars and place in oven at 100 degrees C to dry and sterilise.
Take any green stalks from the strawberries, avoid washing if possible, or at most, rinse gently in a colander. Place in a large pan, preferably a jam or maslin pan, together with the lemon juice and put over a low heat to start the juices running.When strawberries are heated through, remove from the heat and stir in the sugar. Stir gently to dissolve sugar. Place back onto the heat, turn it up higher and bring the contents of the pan up to the boil, then reduce to a 'rolling boil' ( Just high enough so that the jam doesn't boil over.) Stir very occassionally to prevent sticking, but each time you stir the jam it will cool slightly so don't overdo it. When the jam has darkened and thickened slightly, usually after 10mins or so, you can test for a set. Place a small amount, around a teaspoonful, onto one of the cold plates, place back in the fridge for a few moments. To test, gently push the edge of the jam on the plate to see if it 'crinkles' - if so, the jam is ready. Turn off the heat, and leave to stand for at least 20 mins as if you jar it too hot all of the fruit will rise to the top of the jar.
If it is not yet ready, continue to cook for a further 10 mins, then try again and so on. With experience, you will come to know when a jam is ready for testing but that is something that has to be learned.
Remove the jars from the oven, if there is sugar foam on the surface of the jam this can be dispersed by stirring in a knob of butter. Pour the jam into the jars to just below the top of the jar and then seal immediately with a new lid, or cellophane covers. The jam will keep, in a cool, dark place for several years - there is no need to refrigerate either open or unopened.
Leave to stand undisturbed overnight, then make some scones and enjoy!