3 pounds of clementines
8 cups water
8 cups sugar
Cut each clementine in half, then slice the into very thin slices. Add the slices to the water along with the sugar in a large pot. (Use only stainless steel or ceramic lined pots. The acid in the citrus fruit will react with aluminum.)
Slowly bring the mixture to a slow boil, ensuring that the sugar is fully dissolved, then remove from the heat and cover the pot. Leave the mixture in the pot at room temperature overnight.
Next day, slowly bring the pot to a slow rolling boil for about 2 hours, stirring occasionally. After 2 hours, increase the heat to about medium and begin to take the temperature of the marmalade. You want to take the mixture to between 220 and 225 degrees F on a candy thermometer. This is the temperature needed for the pectin to set.
Remove the marmalade from the heat and let it cool before adding it to sterilized mason jars and processing in a water bath to ensure a good seal on the jars.
Store in a cool dark place.