by another_jim on Mon Apr 20, 2009 7:08 pm
The only ASIC contributions are two papers out of Illy's labs, one by Petracco, one by Capuccio, which describe simulations of the espresso extraction. The chapter I quoted has them in the bibliography. The Capuccio paper mentions particle expansion as it wets, and then mass diminution as it brews, but doesn't explicitly mention puck volume. It does mention that the particles don't shrink, rather lose their innards to become cellulose skeletons. That suggests the puck does not collapse during the extraction.
The video by La Spaziale, on the other hand, has not been followed up by any peer reviewed article I know of; nor is the video available for inspection. This makes it a prime example of internet hear say. Given that the Illy volume summarizes the known published science as it stood in the early 2000s, I'd say it's a bit premature to call puck expansion a myth.
This is actually not all that difficult to check, since we have a few people who have mounted pressure transducers inside the group. A pressure transducer at the top of an overdosed puck and under the shower screen would according to Petracco go off the charts as the puck expands to its rock splitting pressure levels. If the LS video is true, it would stay at close to zero until it got sucked out, like Goldfinger exiting his plane, as the three way valve whooshes.
