I wanted to make some orange marmalade for my Christmas baskets, but thought I would try a unique combination. There are a lot of marmalade recipes but I decided to branch out and make up my own. Clementines are one of my favorite citrus and the navel oranges are so nice right now. And just because I had some of my home grown rhubarb in the freezer I threw it in too. Nice!!
Prepare orange rind as follows: Wash navel oranges (about 4 or 5) and clementines (about 10-12 small ones). Using a sharp peeler, pare away only the zest of all the oranges and clementines. Reserve. Stacking several pieces of zest together, cut into very thin strips until you have 2 cups of finely sliced zest. Place the zest into a large saucepot or dutch oven. Add the water to the pot. (From this step, when I use the term oranges, I will mean both navel and clementine oranges.)
NOTE: I have an OXO serrated peeler that was very effective at paring away only the rind/zest of both the orange types. I would suggest that you purchase one of these peelers as they are far superior to others and are razor sharp for ease of peeling any fruit or vegetable.
For the lemon, slice off a thin piece of the ends of the lemon to expose the pulp. Cut in half lengthwise and then slice as thinly as possible with a sharp knife. Deseed the slices as you go and place the deseeded thin slices in the pot with orange peel and water.
Cut the pith off of the "peeled" oranges completely. Remove any stringy inner parts (I find a pair of sharp kitchen scissors great for removing the stringy centers of the oranges) and chop oranges into about 1/2 inch chunks. Measure and add 4 cups to the pot.(it is ok if you have a little more or less)
Turn on the burner to medium high and simmer the mixture for 5 minutes. Remove from heat, cover and let set for 12 to 18 hours in a cool spot.
Figure your gelling point by placing your candy thermometer in a pot of boiling water, noting the temperature and adding 8° to obtain your gelling point. This compensates for altitudes over 1000 ft.
Add cut up rhubarb to the pot and heat over medium high heat. Cook rapidly until the orange/lemon peel is tender. Remove from heat and measure the fruit and liquid into a pot large enough to hold the mixture plus sugar, that will not boil over when cooking.
For each cup of fruit/liquid add one cup of sugar to the pot and stir to dissolve. Bring to a boil over high heat, stirring constantly.
Continue boiling and stirring until the candy thermometer shows that you have reached the gelling point established in Step #4.
If you prefer, you can use the plate test to determine if the mixture will gel. Pour a small amount of the mixture onto a chilled plate and place it back into the freezer until cool (room temp) If you drag your finger through the sample and it leaves a clean mark with the gel slowly flowing back to its original form, it is ready to process.
Remove the marmalade from the heat and ladle into hot jars. Wipe rims and adjust two piece lids until finger tight.
Process in a boiling water canner for 10 minutes or as per directions for your altitude. Remove jars from canner and place on towel lined countertop. When all jars have sealed, store in a cool dark place.
Marmalades are sometimes slow to gel and may take up to 2 weeks to set up completely.