My grandfather would put a piece of eggshell in to settle them - not sure how scientific that is... edit - found this http://blog.khymos.org/2010/08/04/norwegi

My grandfather would put a piece of eggshell in to settle them - not sure how scientific that is... edit - found this http://blog.khymos.org/2010/08/04/norwegian-egg-coffee/ http://blog.khymos.org/2010/08/04/norwegian-egg-coffee/ "When looking into the chemistry behind this it isn’t as strange as it may sound. Fish skin as well as eggs contain proteins. The addition of proteins while preparing the coffee serves two purposes: 1) it helps the coffee grounds to flocculate, allowing them to sink faster to the bottom of the pot (this effect is probably more pronounced when using eggs) and 2) the proteins bind irreversibly to astringent and bitter tasting polyphenols in coffee to form insoluble complexes that will precipitate. The end result is a clearer coffee with a pleasant and mild taste. The bitterness is only barely noticeable, but the coffee still has enough “body” so it doesn’t feel too thin! "