After simmering my chicken stock for 7 hours I still notice undissolved pieces of soft cartilage. I can squish them between my fingers but they aren't completely dissolved. Soft cartilage is one of the primary sources for the collagen that makes soup gel, right? If I want the thickest gel should I simmer it longer? Also, although I've never seen a recipe adding salt to stock before you simmer it, has anyone ever tried it? In theory the salt should raise the boiling point and the collagen should melt faster. Besides that, I'm not sure what effect the salt would have.