The white stock you've just made has turned out cloudy. List 3 reasons why this may have happened. How could you prevent this from happening the next time?
It's the proteins coming out of whatever "white" thing you are making stock from. It's inevitable. To be clear like a consomme you'll need to skim the top and ultimately strain it. You can also use a "raft" of egg whites to collect some of that protein material after it surfaces. You didn't specify what kink of "white" you are asking about. That would be useful to know.
Start with cold water and don't let it boil. Bring to a boil and return to a light simmer. You could also try blanching the bones ahead to coagulate the proteins. I haven't done this, but it should help. If it is still too cloudy, follow peirino's advice. Also, I like to use large coffee filters inside a sieve for straining to get the smallest particles out.