HB wrote:that was Lino's point about nutating action and asphalt compression.

Well, the two aren't really that comparative. Asphalt is no longer compressible when the solids in the mix are all touching and there is no longer room for movement. Once this happens you're done unless you increase the pressure enough to crush the stones in the mix. This may be true for coffee grounds as well, but that would mean that 30lbs is as compressed as the puck can be, and that the bean fragments can not be any closer to one another, nor can they be deformed or compressed any further. My empirical evidence tells me that this isn't true.

You may be right. To test, I would want to compare a 30, 60, 100, 200, and 300 pound tamp. Just guessing, I'll bet the tipping point of no change for a straight-on tamp will occur in the 100-150 pound range. Anyone with a hydraulic press want to test Michael's claim?

If I get a break at work (my laptop HD decided to go on vacation) I will give it a try. I have a hydraulic press back in the maintenance department.

Nah... what you guys really need is a vibrating tamper... just thinking about it, a straight vertical press isn't going to get the particles inbetween the other particles. It's like when I was a kid and saw an in-person demo of Mr. Wizard (or was it Mr. Science... can't remember, but he was the old guy who predated Ken Nye the Science Guy) - he brought up a kid in the audience, gave him a hammer and Mr. Wizard had his hand under a pile of sand. He told the kid to whack away and not a thing happened to his hand! Of course, I promptly repeated the experiment at home... So - use a cheapo massager and a tamper... hmmm... I'm going to make millions I tell ya!!

Geoff

We have a 30 ton hydraulic press, but there is no pressure gauge so it is pointless to try.

HB wrote:We were discussing Mark's article at our usual Friday espresso get-together, specifically about how force is transmitted through different mediums. Ironically Lino had a meeting later the same morning to discuss the minimum nutation necessary to properly compact asphalt, the same principals applying loosely to coffee pucks. I won't attempt to summarize Lino's explanation, other than to say the multiple angles of attack contribute more to the tighter compaction than simply how hard one presses; this may also explain why Michael Teahan's SCAA presentation reported no significant difference between a 30 and 300 pound tamp.

Have you ever try to tamp, putting say a third of the coffee in the pf, then tamp this, then put another third and tamp this and finally put the last third and tamp this?
It is a question only.

Theodore wrote:Have you ever try to tamp, putting say a third of the coffee in the pf, then tamp this, then put another third and tamp this and finally put the last third and tamp this?

Yes, years ago I tried mid-tamps as Jon described them in his article How to make a beautiful "naked" triple espresso. *shrug*

I think wet pucks occur due to the moment of stopping the pump and delay with taking the portafilter out of the group, at least with the beans I use on my machine I noticed it.