More Summer fruit: Elderberry Sirop

I can't resist it. I must tell about the elderberries.
A. saw them glimmering in the tree tops, and remembered a friend in her student house, who had elderberry sirop -- made by her grandmother -- which she would drink, diluted with warm water when she was ill. So A. went out with a few buckets and picked them full.
We boiled them down to juice, strained them through an old tea towel in a collander. Washed and washed the blue/purple/pink mess on the counter top, the collander, the tea towel. Then we measured 1 kilo of sugar to each liter of juice and the juice of 2 lemons per liter. Brought to the boil and simmered for 5 minutes. Then bottled.
It tastes wonderful: sweet and yet earthy. We have no idea how it will keep. Once opened A intends to freeze it in the ice cube tray. But the colour of the juice itself is already a feast!