NOTE: If you can not get hold of jam sugar and choose to use the Liquid pectin - add it to the mix at the beginning of step 3.
To test for a set: before starting to make the jam put a couple of saucers or small plates into the coldest part of your fridge. When you think the jam has reached setting point, place about a teaspoon of the jam onto one of the cold plates and leave for one minute. Then gently push your finger through it. If it wrinkles / rises up your finger nail it is ready.
If you are new to jam making I have a recipe posted that shows and explains about the various equipment I use.