Purpose of the Tamp

[lee]

As I've doubled down on developing my Barista "skills" I naturally find myself exploring the meaning behind each step. While tamp pressure and grind are understandably linked (dosage fixed), I'd like to know how the Forum views the interplay of these two variables. For example, is it best to make the grind as fine as possible, thus reducing tamp pressure? Or is there a minimum tamp pressure required?

It seems - from my unschooled perspective - that one would want to grind as fine as possible, and tamp as light as possible.

Thanks,

Lee

[another_jim]

There's not that much of a trade-off between tamping and grind. A much heavier tamp will allow maybe a very slightly coarser grind. Tamping is important if your espresso machine comes to full pressure very quickly, or if a gap remains between the shower screen and top of the puck after it has expanded with absorbed water. In this case, a heavy tamp keeps the puck from melting. If your machine ramps up slowly (6 or more seconds between turning on the pump and seeing the first drops), and if the puck expands into the shower screen, then tamping is not particularly important.

Much more important is levelling the ground coffee before you tamp so that it is evenly dense throughout, and there are no air gaps between the basket rim and puck or inside the puck. A naked portafilter will quickly indicate if you are having any problems in this area.

It could be that grinder technology has improved, or at least changed, in the past 40 years. I remember heavy tampers being used in my grandparents restaurant on lever machines in the late 50s, even though these preinfuse for 10 seconds, and would not require much of a tamp with today's grinders. I do not know if tampers were used in pre-lever espresso machines that infused at boiler pressure.

[roblumba]

What's preferrable. A finer grind and lighter tamp? If you have a ramped pre-infusion, then you can get away with a finer grind and lighter tamp. But does this help the espresso or not? I've never compared.

[malachi]

Tamp merely preserves the even distribution within the bed while creating sufficient resistance to the initial pressure to avoid water finding ways through the bed.

What matters beyond the above is consistency.

This being said - I (among others) feel that quality is consistently better (and more forgiving) when grind is coarser.

[Ken Fox]

As I've doubled down on developing my Barista "skills" I naturally find myself exploring the meaning behind each step. While tamp pressure and grind are understandably linked (dosage fixed), I'd like to know how the Forum views the interplay of these two variables. For example, is it best to make the grind as fine as possible, thus reducing tamp pressure? Or is there a minimum tamp pressure required?

It seems - from my unschooled perspective - that one would want to grind as fine as possible, and tamp as light as possible.

Thanks,

Lee

In my opinion, dose trumps everything else. By this I mean, if you increase the dose in your portafilter by even half a gram, the impact of tamping and grind are diminished significantly.

I agree with everyone that distribution is important and that some slight degree of tamping, to help with distribution if nothing else, is worthwhile. I doubt that I have tamped any puck beyond 2 or 3 or 5 pounds in the last several years. And it is true, undeniably so, that some things decrease the flow of water through the puck (finer grind, harder tamp) and some INCREASE it (the inverse, e.g. coarser grind, lesser tamping force)."

But, I think you will find that as long as you are consistent with tamp level and grind, that the biggest bang for the buck in adjusting shot flows is the dose of the coffee in the PF, and the smallest variation in dose will have the largest impact on the time/volume relationships in the shot glass.

Everything else is tinkering around the edges, other than for preinfusion (or delayed pressure ramp up however it is accomplished) which does make errors on the other parameters more easily forgiven.

ken

[roblumba]

Wow, that seems very light. 5 lbs. You must have to go very fine on the grind and large on the dose to accomplish that. Do you get the tiger striped ristretto shots with that technique?

[Ken Fox]

Wow, that seems very light. 5 lbs. You must have to go very fine on the grind and large on the dose to accomplish that. Do you get the tiger striped ristretto shots with that technique?

yes

[lee]

Thanks, aJim, Malachi, & Ken. Your input confirms my observation that there's not a lot of interplay between tamp pressure and grind, whereas the process is strongly affected by dose. I realize this is Barista 101 stuff, but there's something reassuring (to me) about a process that consistently reverts to fundamentals. From here I can let go and enjoy the outcome.

As an aside, I find the Marketing challenge for this type of cuisine fascinating; the ubiquity of coffee in everyone's consciousness makes this a vast latent market to be realized. Still, there is a vexing gap to be crossed, and it seems bottlenecked on the supply-side around a class of highly skilled labor which is often not perceived that way; everything else, the raw materials, technology, & distribution footprint are all in place. Or... this is how I would frame the issue for a client who was faced with this challenge. I'm curious if the Roasters see it this way, or if there's something missing in the above hypothesis.

Thanks,

Lee

[HB]

In my opinion, dose trumps everything else. By this I mean, if you increase the dose in your portafilter by even half a gram, the impact of tamping and grind are diminished significantly.

I've not tried your recommendations, but I wonder if the heightened importance you place on precise dosing is directly related to the modest tamp. Afterall, the grouphead dispersion screen (or expanding puck) is doing the tamp for you; wouldn't the dose being off by even a teenie bit amplify the negative consequences compared to a more manly tamp?

[roblumba]

I find that a large dose needs a strong tamp in order to adequately clear the dispersion screen. And it's very important to be level at the larger doses or else the higher side of an unlevel dose will be ruined by the dispersion screen. And of course, I go for a courser grind for larger dosage.

[barry]

but I wonder if the heightened importance you place on precise dosing is directly related to the modest tamp.

no.

[Ken Fox]

no.

why?

ken

[barry]

because variations in dose result in variations in shot time, for any given grind. if one is inconsistent in dose, then one can often chase grinds settings and/or other variables, or blame other things (water temp variations, etc) in looking for reasons for differences in shots.

[Ken Fox]

because variations in dose result in variations in shot time, for any given grind. if one is inconsistent in dose, then one can often chase grinds settings and/or other variables, or blame other things (water temp variations, etc) in looking for reasons for differences in shots.

I was just trying to force you to write a complete sentence.

ken

[barry]

bastard.

[HB]

because variations in dose result in variations in shot time, for any given grind.

No argument there. My (wholly unproven) assertion was that a small variation (say 0.5 grams) would negatively affect the extractions of no-tamp barista more than the barista tamping 30-40 pounds.

[barry]

My (wholly unproven) assertion was that a small variation (say 0.5 grams) would negatively affect the extractions of no-tamp barista more than the barista tamping 30-40 pounds.

i don't see how it would matter.

[Ken Fox]

i don't see how it would matter.

Truth be told, ground coffee is not really all that compressible. In my terribly humble opinion, tamping only matters for the brief period of time before the whole puck is saturated; it may effect, in combination with such things as pressure ramp up times/preinfusion, the likelihood of channeling, which of course will have a major impact on shot timing if it occurs.

Assuming no channeling, and a fully saturated puck, the mass of coffee in the PF is going to effect the timing of the shot from the very beginning to the very end.

I do think this is an onion that can be sliced all sorts of ways and it is hard to make blanket statements about the importance of any one aspect of it. If you find a technique that works for you on your equipment, and you are happy with the results, there is no reason to change. There will also be machine factors that will make some techniques successful on a given machine that might not work on others. And, there are modifications (such as the delay on make timer that Michael Teahan suggested I put in on my rotary) that impact this as well.

From a couple of weeks of daily use of the modified rotary, I can now state unequivocally that preinfusion, done in the way my machine has been modded to do, makes espressomaking easier and there are many fewer sink shots. This is to say that the system is now much more forgiving of barista technique errors and variation than before.

ken