So this has happened to me: I bought a pack of pretty well-looking coffee, using the same approach as for other coffee beans (even the ones from the same "brand") I prepared an espresso, and (to my surprise) got a coffee puck so unbelievably porous that all water just passed through it without any apparent resistance. Of course, no pressure means no crema and no real flavor was generated in this process, so I went for debugging it.
So far, I tried changing the grind to "basically dust" (porlex 0 clicks :] ), trying all possible extraction schedules and pressures, tamping with way more than 20 pounds of pressure, and cleaning my already clean grouphead just to be Super Sure, but all water just goes through.
All other coffee behaves normally (fortunately!). That leaves me wonder what's the actual problem. I can rule out a problem with the age of the beans (I've made reasonable coffee from older ones), and there's no roasting flaw that would be apparent.
- Is there any known property of the coffee that affects the porosity this much? (I guess this can make sense for some preparation methods, but really not for espresso... I'm asking mainly for some possible extra coffee chemistry knowledge that I could have been missing, not really for debugging these precise beans -- I can use successfully them elsewhere.)
- Is there anything else to do with it, given I've already maxed out grind, weight, brewing pressure and all other things?
ADDITIONAL DETAILS (edit): Beans were Indonesia Mandheling arabica, mix of several varieties, altitude 1100-1600m, wet-hulled. It seems they were roasted just under 2 months before the experiment, packaging seemed okay to me. The roast is relatively dark with a tiny bit of oil visible here and there (just below "full city" I'd guess). The bag has the usual degassing valve. The puck didn't look particularly chanelly (top: not perfectly level but no noticeable dents/holes or prominent problems, bottom: almost uniform color with a slightly "brighter" middle). I unfortunately don't have that particular coffee anymore to try more.