Wash jars and lids, place jars in pot fully submerged in simmering water, recipe makes 3 to 4 half pints (4 oz) jars
Peel oranges, remove pith (less pith, less bitterness in jam) and cut into small pieces and add to a blender
Blend into a smooth juice
Put sugar, lemon juice and zest in a saucepan over low heat and stir to dissolve, about 5 minutes
Add blended oranges and pectin to the saucepan, bring to a boil and simmer for 10 minutes
Turn off heat, remove jars from water bath and wipe rims with vinegar soaked cloth
Fill jars to one inch head space, add lids and rings, finger tight, and return to water bath.
Process on a boil for 10 minutes, remove and allow to set for 24 hours. remove rings, check seals, label and store