Here is an exquisite jam without preservatives or thickening agents. It’s hard work, but it’s worth it!
Green grapes or sweet purple grapes, sugar
Wash the grapes carefully, pick off the grapes from the rasps, eliminating the spoiled ones, and patiently remove the seeds, keeping mind to collect the juice in a bowl. Weigh the grapes after the process. For every kilo (2 ½ pounds) of cleaned fruit, 400 grams (1 ¾ cups) of sugar will be needed. Put the grapes and the juice in a large steel pot and cover it with the sugar. Turn on low heat and let it cook for about 10 hours without touching it. Then, stir with a wooden spoon, for about an hour until the jam thickens and homogenizes. Remove from the flame and put the jam immediately in the jars, adding a thin layer of sugar on top. Put the lids on while they are still hot, and turn them upside down, leaving them so till the following day.
Store them in a cool, dark place.