Why do some people put eggshells in coffee grounds?
This is bit of folklore that has been explained in at least two different ways. Some old cookbooks claim that the eggshells help to clear the coffee by attracting floating grounds and then precipitating to the bottom; some of these old recipes call for adding an entire raw egg. Less commonly, adding eggshell to the grounds of coffee is said to reduce bitterness (though improving the coffee to begin with would be a better tactic.
