Makes about 11 8-ounce jars or about 7½ 12-ounce jars
3½ pounds oranges, preferably unsprayed and strongly flavored; avoid very sweet oranges
5 cups water
½ cup fresh lemon juice
1 box MCP pectin
9½ cups cane sugar, pre-measured in a separate bowl
12 8oz canning jars, washed and kept warm; boil canning jar lids in a small pan and hold in simmering water.
Cut off ends of oranges, slice thinly (1/8 inch), and remove seeds and any pith in center of slices. Cut large-diameter slices in half
Mix oranges with 5 cups of water and ½ cup lemon juice in a large, non-reactive pot. Bring to a boil. Reduce heat and simmer for 1 hour, uncovered. While oranges are simmering, prepare canning jars and lids.
Measure the cooked fruit and add water or simmer longer to make 7 cups.
Add 1 box of MCP pectin (2 oz) and mix thoroughly.
Return the fruit mixture to high heat, and bring to a full rolling boil, stirring constantly.
Stir in 9 ½ cups sugar, and bring to a full, rolling boil for 4 minutes.
Remove from heat immediately, and stir for 5 minutes to prevent floating peels.
Fill hot jars to 1/8 inch below rim. Wipe off jar rims and cover quickly with lids.
Place rings on jar tops and tighten tightly. Invert jars for 5 minutes to distribute peels evenly in jars. Turn jars upright.
Shake jars gently several times while they are cooling to evenly distribute the peel.
When jars are cool, lids should be dimpled in, indicating they have sealed; if any jars have not sealed, refrigerate and use them soon!
Store in a cool, dark location.