Seeing people use the plastic tamper thingy in front of the doser made me think: Why use so much pressure when tamping? How I picture it: The Italian style tamp (using the plastic tamper thingy or just the weight of a nice metal tamper) might make a distribution defect show up more pronounced because the uneven density doesn't get compensated by the tamping, whilst a perfect distribution will still produce the same result because the water pressure will be the same everywhere (the coffee won't be stirred up then, right?). Of course one might want to adjust the grind settings...

Comments please?

Tamping is just a way to preserve the coffee bedding.

I have to disagree that tamping does not aid in distribution.

In my opinion, It DOES.

Think about it. If you have a pile of sand in your sandbox and push down on top, what happens? It goes out to the sides, redistributing the grains of sand more evenly. In fact, this doesn't require a lot of pressure to accomplish.

The same with coffee grounds, to a point. At a certain point, the grounds will interlock and any added compression force will be absorbed by the mechanical torsion of the multigrain structure of the bed, much like a strain gauge, unless enough force is applied asymmetrically to the bed to disrupt the structure (which is how we get cracks and fissures).

So basically, a light tamping force helps to redistribute the grounds a bit.

A firmer tamping force makes a solid bed that might resist the water's disruptive force that can redistribute the grounds. To a point it will also compensate thusly for a coarse grind.

A very firm tamping force increases the risk of channeling.

drdna wrote:I have to disagree that tamping does not aid in distribution.

In my opinion, It DOES.

Maybe I didn't make myself clear enough (sorry 'bout my language abuse ) but that's exactly my point. In my opinion (and I think I'm not the only one) the distribution is what counts. Everything you do afterwards (redistribute, tamping hard etc) is just a fix and the aim should be to minimize these rituals...

Think about it. If you have a pile of sand in your sandbox and push down on top, what happens? It goes out to the sides, redistributing the grains of sand more evenly. In fact, this doesn't require a lot of pressure to accomplish.

The same with coffee grounds, to a point. At a certain point, the grounds will interlock and any added compression force will be absorbed by the mechanical torsion of the multigrain structure of the bed, much like a strain gauge, unless enough force is applied asymmetrically to the bed to disrupt the structure (which is how we get cracks and fissures).

Yes it is an interesting point you make (I've already read it elsewhere) and I'm pretty sure this must be what happens... Still I'd like to see a physical simulation or some other quasi-scientific research.

So basically, a light tamping force helps to redistribute the grounds a bit.

A firmer tamping force makes a solid bed that might resist the water's disruptive force that can redistribute the grounds. To a point it will also compensate thusly for a coarse grind.

A very firm tamping force increases the risk of channeling.

That would be another reason to avoid hard tamping...

...Sadly i don't have an x-ray apparatus...
Ask a dentist to help.He has.

I wish folks here would write "my hypothesis is ..."
Regards, Henry

hbuchtel wrote:I wish folks here would write "my hypothesis is ..."
Regards, Henry

It is...

LGB wrote:Yes it is an interesting point you make (I've already read it elsewhere) and I'm pretty sure this must be what happens... Still I'd like to see a physical simulation or some other quasi-scientific research.

It is extremely well described in numerous experimental studies in the analytic and physical chemistry of laminar and nonlaminar flow of particulate solids. This is much more a concern to geologists and construction engineers than espresso makers. If you enjoy mathematics, you can find something here. Not the exact article I was looking for, but it gives you an idea of what you're in for.

One implication is that by pouring a slurry of coffee grounds and water, we can eliminate channeling. This works extremely well in the experiments I have done, but ends up acting like an extended preinfusion, so the resultant cup has a lot of drip coffee character. Oh man, that is getting off topic.

If look around a bit, there has to be an Italian university paper on this, they have one on everything else involving coffee.

LGB,
This is off topic, but your signature line is not quite correct.

LGB wrote:"A mathematician is a device for turning coffee into theorems."~Paul Erdõs

Most everyone knows that Paul Erdõs was a mathematician who turned amphetamines into theorems. He found those more effective than coffee.

In fact, according to Wikipedia's artical on Paul Erdõs:
"His colleague Alfréd Rényi said, "a mathematician is a machine for turning coffee into theorems", and Erdős drank copious quantities. (This quotation is often attributed incorrectly to Erdős himself.)[7] After 1971 he also took amphetamines, despite the concern of his friends, one of whom (Ron Graham) bet him $500 that he could not stop taking the drug for a month.[8] Erdős won the bet, but complained during his abstinence that mathematics had been set back by a month"

http://en.wikipedia.org/wiki/Paul_Erd%C5%91s

Oops! Fixed.

hbuchtel wrote:I wish folks here would write "my hypothesis is ..."
Regards, Henry

My hypothesis is ... if the moonbeams are well distributed in the jar there is no need to tamp them.

Yes, but can you take them home?