1. Physics of a Good Coffee Andrei Varlamov COHERENTIA INFM-CNR, Roma Giuseppe Balestrino Universita’ “Tor Vergata”, Roma Wroclaw, September,15 2006

2. Italian Moca

3. Filtration: the Darcy Law atm +  P P(T)=P atm +  P }  P = Q  L/(S  κ)  ( °C) = 10 -3 Pa s  P  4· 10 4 Pa → T* ~ 110 °C Q = m/t~200 g/min L~ 1 cm atm P=P atm → Q = κS  Pρ/ (  L) S~ 10 cm 2 κ ~ 10 -12

4. The limitation of the Darcy Law at small pressures: opening of the cappillars

5. Moka explosion. κ ~ 10 -12 κ ~ 10 -13 ~ 10 -14 M=150 g, V=200 cm 3 T max ~ 300 0 C→P max ~ 10 3 atm E ~ PV ~ 40 KJ → v=200 m/s PV=m/μRT

6. Espresso machine