if you add some butter to the sure jell and juice it will keep it from foaming and you will not have to skim it off.

You'll need a little more than a gallon of black raspberries for 4.5 cups of juice. But let me tell you, this jelly is fantastic! You'll never want to buy store jelly again. Make sure you get a good boil after the sugar and boil for exactly a minute. You'll be be able to tell the boil as the mixture will rise a little in the pot and you'll get a foamy boil - it even feels different. Never stop stirring during both boils. I usually don't add butter and I don't skim. 5 stars!