Cut fruit in half, squeeze out juice and pulp, discard seeds. The volume of this should be approximately 4 cups. Remove zest, this should yield approximately 1/2 cup. Transfer juice, pulp and zest to a large glass bowl. Cover and refrigerate for 24 hours. This helps the peel to soften.
After soaking, put the citrus in a large stockpot. Add 6 cups of water, simmer for 1 1/2 hours. A sample of the peel should feel quite tender if rubbed between fingers. Add sugar and ginger. Bring to a boil, stirring constantly with a wooden spoon. Boil hard for 20 minutes until sugar is dissolved and mixture is thickened. If the mixture foams up, add a pat of butter and the froth will subside.
Test for jell-point: drop a small amount of hot marmalade on a chilled plate. Return to the freezer for 1 minute. If surface forms a skin, it has reached jelling point, if still syrupy, continue cooking and test again in 5 minutes.
Remove from heat, stir in pectin. Cool for 15 minutes, spoon into half-pint sterilized jars leaving 1/4-inch headspace and seal.
** Recipe Note: Traditionally the citrus seeds and pith are enclosed in a nylon bag and boiled along with the juice/pulp. This releases the natural pectin that is stored in that part of the orange. For time and ease, we eliminated that step and used store-bought fruit pectin. It worked very well.
***To sterilize the canning jars, wash the containers in hot, soapy water and rinse. Boil them in a large pot for 10 minutes. Keep the jars in hot water until ready to use to prevent the jars from cracking. Dry with paper towels before filling with marmalade. Once filled, put on lids and collar. Boil again for 10 minutes to seal the jars.