Wash the currants, remove the berries from the panicles. Weigh 1.4 kg of pulp. Mix currants, syrup and jam sugar well in a large pot. Heat while stirring. Simmer for about 4 minutes while stirring until bubbly. Skim off any foam that may have formed.
Fill jam immediately into clean jars with twist-off lids and close them tightly. Turn glasses upside down for about 5 minutes. Turn upside down again and let it cool down. Store jam dark and cool