You can also use a teaspoon of sunflower oil..... If I think it is ready I do the methylated spirits test to check
Didn't know you could use oil instead so thanks for that tip. What's the methylated spirit test? please
When you have slowly and lovingly simmered your fruit to extract the pectin, take the pan off the heat and take out a teaspoon of the fruit and put it in a small jar of methylated spirits.
Wait for a minute or too and look at the fruit.
If you have a firm lump of jelly you have high amounts of pectin,
if the fruit holds together it is a medium pectin,
if it barely makes a blob you have very little pectin and are unlikely to get a set unless you add some extra pectin in the way of the liquid certo, or a pectin stock or the addition of grated bramley apple that has been simmered in a little water and then added to the fruit.
Some books tell you to add more lemon juice but the lemon juice is usually added to help release the pectin in the fruit.
I usually do this test as pectin levels in fruit can vary.
Also if you boil the fruit hard and quickly at the beginning of the jam making process you can actually kill off the pectin. Low and slow at the beginning before you add the sugar is best.
Also with strawberry I find that simmering long enough to reduce the water content of the fruit also helps with the set.
