Damson jam

[milkmoustache]

Just picked a huge bag of damsons and i want to make jam with them. As with last year, they are very sweet, so much so that you can eat them raw without shrivelling the inside of your mouth, so I need to reduce the amount of sugar - but am a bit of a jam novice and have no idea how much I can reduce it by... So - for 1 k of damsons, how much sugar?

no idea about sugar ratios but some damsons are sweeter than others ; some you can eat raw other's you can't

If they are sweet, I'd say about 800g