The egg is mixed with coffee grounds and a little cold water before brewing. As it heats, the egg proteins coagulate and help trap fine coffee grounds and some bitter compounds.
The crushed eggshell contains calcium carbonate, which can slightly reduce coffee’s acidity. The result is usually a clearer, smoother cup with less bitterness and sediment.
This unusual technique has roots in Scandinavian and Midwestern traditions and was especially popular at churches and community gatherings. Although it sounds strange today, many people still use it for its distinctive smooth taste.
