I've made this in previous years, sometimes successfully and sometimes not, but I haven't given up on it. Usually my failures have had to do with making too much at once - the cooking process takes significantly longer in those cases which gives more opportunity to ruin a perfectly simple recipe.
However, after last week's mostly successful experience with the Meyer Lemon marmalade this recipe (originally a photocopy of a handwritten recipe from one of my Farmers' Market vendors) became much clearer. So instead of slavishly following the recipe I made up my own. See what a little experience and success will do?
Take two baskets (the size that strawberries come in) of washed and de-stemmed kumquats (the tart variety), sliced with the mandolin attachment of the food processor and place in a glass bowl. Add water to just cover. Ignore the seeds. Let sit at room temperature overnight.
Place in non-reactive pot and keep at a slow boil for about 30 minutes to reduce volume by about 25% while occasionally spooning scum off the top. You'll need to get as many of the small seeds as possible.
After about 30 minutes, measure volume in cups or estimate carefully. Add no more than 3/4 C of sugar per one cup of boiled kumquat mixture. (The original recipe called for 1 C sugar per cup of kumquat mixture, but that has been too sweet for me every time I've made the recipe. Even the 3/4 C : 1C ratio I used the other night proved to be almost too sweet for me.) Taste the marmalade and if too sweet then you can add half a very finely chopped Meyer Lemon (smaller pieces will cook faster) and/or some lemon juice.
Incidentally, the Meyer Lemon that I picked for duty last night was much more fragrant than last week's lemons from the same tree. I think that the couple days of hot weather really ripened the fruit and brought out the flavors. I have to remember that in coastal California things tend to ripen several weeks later than elsewhere in Ca.
Boil slowly, stirring occasionally to prevent sticking while continuing to spoon the scum and seeds off the top. Place a plate in the fridge, and cook the marmalade until a blob of the hot liquid turns to your desired jam-like consistency when placed on the plate.
Preserve in the usual manner or just ladle out into clean glass jars and keep refrigerated.