Recipe yields 7 half-pint jars.

PREP FOR CANNING

• Prepare calcium water from Pomona pectin. Put 1/2 teaspoon calcium powder (the small package) and 1/2 cup water in a small jar with a lid. Shake well before using.
• Wash the jars you'll use in hot soapy water, making sure clean jars are free of nicks in the rim, which could impede sealing.
• Place empty jars in a canning pot with enough water to cover by an inch or two, cover pot, and set on high heat. It can take awhile for the water to heat, so get it started before you begin making the recipe.
• Wash canning lids and rings in hot water; set aside.

MAKE THE MARMALADE

• Wash lemons and use a vegetable peeler to remove just the yellow portion of the skin from 4 of the lemons. Use a sharp knife to cut these into narrow strips, 1” long. Set aside.
  8 lemons
• Remove the white pith from these lemons, and the entire peel from the remaining four. Chop lemon segments into 1/4-1/2” pieces. 
• Combine the chopped lemon, lemon peel, and water (along with ginger and cinnamon if using) into a large saucepan. Bring to a boil, reduce heat, and simmer for 20 minutes, stirring occasionally.
  3½ cups water, 2 cinnamon sticks, 2 inch fresh ginger
• Transfer hot mixture to a mixing bowl; discard ginger and cinnamon. Measure 6 cups of the fruit mixture back into the saucepan along with the calcium water. Stir well and return mixture to a filling boil over high heat. 
  4 teaspoons calcium water
• Meanwhile, combine the sugar with the pectin until it's thoroughly combined.
  3 cups sugar, 5 teaspoons pectin
• When the lemon mixture comes to a boil, stir in the pectin and sweetener, stirring vigorously for 1 to 2 minutes to dissolve the pectin while bringing the jam back to a boil. Remove from heat when the jam boils.

CANNING THE MARMALADE

• Ladle hot jam into quarter-pint, half-pint, or pint sized jars, leaving 1/4" head space. A canning funnel makes this easy.
• Wipe jar rims to remove any jam that may have spilled. A clean rim is essential to a good seal.
• Set jar lids in place. Screw bands on finger tight.
• Use a jar lifter to gently submerge jars into hot water in the canning pot. Water should cover the top of the jars by an inch. The water will cool somewhat in reaction to the addition of the jars. Return the water to a simmer and then set the timer.
• Process jars for 10 minutes 0-1,000 feet altitude; add an additional minute for every additional 1,000 feet in elevation.
• Remove jars from the boiling water bath using the jar lifter and transfer to a solid, towel-covered surface. Allow to cool for 24 hours.
• Check seals. Lids should be solid and pulled down tight. (if they flex and pop, the jar didn’t seal; put unsealed jars in the refrigerator and use those first).
• Remove rings and wash outsides of jars. Store in a cool place.