Turkish street coffee uses a sand-filled pan: the pot, called cezve, has coffee and ground coffee inside. It 'magically' fills up almost immediately because the pan is very hot.
I feel stupid for asking but I googled and the "simple" explanation I found confused me even more.
it's "filling up" because the water is boiling. the sand surrounds the vessel on all sides except the top, and it's not a very big pot.
So "Full up" just means - full up with foam? It's as simple as that?
Coffee has an oily texture that slightly increases water's surface tension, so boiling water with coffee has a thicker foam due to the oils on the surface. Additionally, the coffee is finely ground, even more than espresso, so that it forms a cloudy/dirty silt that settles to the bottom of the cup when its not disturbed. The boiling action disturbs the silt and mixes the coffee with the water. Once poured, you let the coffee sit to cool and let the grounds drop to the bottom of the cup. You carefully sip so that you don't disturb the coffee silt layer.
Turkish coffee technique takes advantage of these properties.
