In general if the setting point is achieved then the jam (preserve, jelly, cheese or butter) will set. However in some cases low levels of pectin will mean that a perfect set is not achieved.
- If you have a thermometer the temperature should be 222F / 106C .
- You can put a small amount of the jam on a plate and wait for it to cool. If a skin forms or the mixture wrinkles when gently pushed with your finger, this is an indication of setting point.
If you have made and put your jam in jars and found it has not set, just return the jam to your preserving pan, bring back to the boil and add the juice of a lemon, this should help.