It is essential for your jam to reach setting point. There are several ways to test that the jam has reached the correct temperature for setting. Two are economical in that you probably already have these in your cupboard and the third may require you to buy something extra.
Some people get on with either the plate or the spoon testing methods while others do not. Personally, I prefer not to guess and use a jam thermometer especially as my old hob makes it hard to even get to the temperature anyway.
Using The Chill a Plate Method to See If your Jam Has Set Yet
My mum always used The Plate Method or the wrinkle test as it is called when she made her jam to test the jam’s setting point. Using this method her jam always set. (Mine didn’t) This is where you chill a plate and then test the jam on that plate. If the jam is at its setting point it will start to set and will remain in place and wrinkle when the plate is turned on its side or you run your finger through it. If the jam is not ready then it will begin to slide off of the plate.
The Spoon Test to See if Your Jam Has Set
The Spoon Test You need a metal spoon to use this method. Cool, the spoon. Pop the spoon into your jam mixture when it is bubbling and you think it is hot enough. Remove your spoon and lift it. Turn it on its side. The jam should not drip rapidly but rather it should form several drips on the spoon.
Using a Thermometer for a Jam Set Test
Thermometers After three failed sets of jam using the above two methods when I started out I gave in and got a thermometer.
In Conclusion
Many sites and books recommend that beginners start with a thermometer anyway. I haven’t looked back since. What I didn’t know at the time was that although my jam looked hot and was bubbling, it was just not hot enough.
My hob just didn’t cut it. Also, I was using a saucepan to try and save money. Together this meant that the reason my jam wasn’t setting and also the reason the other methods didn’t work was simply because my equipment wasn’t good enough to get the jam as hot as it should be. Even with a thermometer it only just made it to temperature.
Another reason for your jam, not setting could be because you have not got enough pectin. It could be a low pectin fruit.