The last few batches have been closer to gravy in consistency than jello. Im kinda confused. Normally I make bone broth with the bones of a whole chicken that has been roasted. This time I bought some chicken carcases and feet from the meat guy at the farmers market. I made bone broth as usual. Same amount of time, in a crock pot and using the same standard additions (onion garlic etc). Even this last batch in which I added a few leg bones that had been roasted.. still.. gravy???
Sometimes when you cook bone broth for a long time the gelatin "breaks down" in a sense and doesn't gel, but it's still there (with all its nutritional goodness). I've heard this before, and it's the only explanation that makes sense as to why sometimes my stock gels and sometimes it doesn't, even when using the exact same bones/recipe and cooking time. If I only cook my broth for 6 hours, it gels perfectly, but I can't believe there are as many minerals.
Get a pressure cooker. Collagen breakdown accelerates significantly at higher temperatures (a 15psi cooker is by definition at 250 F). One hour is enough to get solidly gelled chicken stock every time as long as the raw ingredients have plenty of cartilage on them.
i have done bone broth in the pressure cooker for 40minutes to hour after the pressue top pops up and i put it on low heat. this was with lamb (neck) but with the meat on however still had some gelatin set nicely in the fridge. let the broth cool then pour and sieve into glass jars and place in fridge overnight. thats what i do and it works :D