It is nigh impossible to get any kind of pectin type crystals here in Scotland. We have to do everything possible to ensure that our jellies and jams set. These are a few things to help:
1. Pour the required amount of sugar into a microwaveable container and warm up in the microwave for 3 minutes to ensure that the sugar is warm when it meets the warmed liquid.
2. Add extra lemon juice - about 1 tablespoonful.
3. Take the telephone off the hook or ignore any calls.
4. Make sure you have a rolling boil, i.e. when stirred the boiling still keeps bubbling.
5. Depending on the heat radiated by your heat source, the jelly/jam can take anything from 10 - 15 minutes to reach setting on a full boil.
6. No matter how fed-up you are standing stirring, don't be tempted to jar too soon. Keep taking a teaspoonful of the jelly/jam and testing on a cold saucer until you have a crinkle on the top, when pushed with finger. There is nothing worse than 6 jars of unset jam/jelly and having to start the whole process again and having to re-sterilise your equipment.
7. Remove any scum, particularly when making jelly. Scum in jars of beautiful coloured jelly looks unsightly. Stirring in a teaspoonful of butter, before potting, disperses any scum.
8. If making different types of jelly over a couple days remember to label when cool so you don't mix up the jars and put on the wrong labels.