Blackberry blanks

Everyone knows that berries are a source of a wide variety of vitamins that we need so much. But once in the store, sorting through the berry "assortment", I came across blackberries and thought, why not try it?! I read at home that blackberries are rich in glucose, fructose, vitamin C, and also helps with colds and stomach diseases and even protects against cancer - and bought. The recipe for harvesting blackberries is as simple as other berries. Of course, it is better to use freshly picked berries, but not everyone has the opportunity to get out into the forest.
Blackberries are quite a tender berry. If you use frozen, then you need to defrost at room temperature.
If you have leaves, you can cook a decoction of blackberry leaves by boiling it for 20 minutes.
Then I measured out one glass of broth and boiled syrup on it, adding sugar (preferably pure and white).
If you don't have leaves, then just cook the syrup (1 liter of water per 1 kg of sugar).
Next, add blackberries to the syrup and leave until the berries release their juice. It will take about two hours. Then add citric acid and cook for another ten minutes.
Immediately pour the jam into sterilized jars and roll it up.