In article 0>,
Wayne Boatwright > wrote:

> I generally simmer a stock for about 8 hours, remove all solids, then
> continue to simmer until what remains will coat the back of a spoon.

Which, I think, is one of the keys. Boil hell out of the bones. When you
get bored, boil them some more. When you get sleepy, boil them some
more. I've noticed this with pigs feet for posole. I only assume it
works for beef bones, although apparently, it does.

leo