To tamp or not to tamp - Page 2

[peacecup]

Noel,

If you have some time and a little coffee to burn, try a simple experiment (which I have not done so far!). Get a coarse, hard-tamp shot dialed in, and a fine, light-tamp shot dialed in. You'd need to use two grinders, or at least get the settings pre-determined. Next, just pull the two shots - in you case you could do so simultaneously on the 2-group Lusso. It would be interesting to hear your results. I may try to do so myself when I get my next batch of fresh beans. I'll just set up two different hand grinders, and do a mini taste test.

I have not read where many folks have really given much effort to dialing in a coarser-ground shot. If you use the "tamp as hard as you can" approach, you will dial in the coarsest grind that will give an ~ 30-sec shot. I know, because I used this method when I first got my Export. I gradually gone to a finer grind under the (untested) hypothesis that a finer grind will give a better extraction. At this point it is rare that I can't adjust my tamp "on the fly", i.e. by judging the dose, bean, etc., and get a good pour from most any grind. If my grind looks finer than it should I tamp more lightly, etc.

It seems to me its just as easy to be consistent with a hard tamp as it is with a light one. It may be that one needs to experiment with each bean/dose combination to get a pour suitable to ones taste.

RE; your post, I'm not sure about the hydrodynamics. It seems to me that a non-compacted mass (ie light tamp) would be very unstable when first exposed to the brew water, and that the surface layers at least would be disturbed. I've always assumed that this would lead to channels being formed in the "puck", causing an uneven extraction. A firmly-tamped a polished surface would act as a buffer, allowing the puck to remain intact while water slowly infuses it. Think of an earthen dam being hit by water, for example, vs. the same pile of earth that was not compacted. All untested theory....

PC

[narc]

PC, there is one "problem" with the Ponte Vecchio Lusso 2(PVL) in running a grind/tamp side by side. The problem has been consistent no matter what blend or SO coffee I have been using. The left group always pulls a slightly sweeter espresso. Why? Not sure. The flow volume/time out of an empty portafilter is pretty much identical if you time from when the water 1st appears to the set volume. The difference is when the water first appears relative to the lever postion. I'm assuming that might be the reason. The way I pull shots on the PVL is: Pull the lever down, hold for a 3-4second count preinfusion, release, wait until the first drops appear in 1-2 seconds, pull and release. Have not figured out, actually too lazy to figure out a way to compensate for the difference between the two groups. I look at the slight differences in taste as a positive since it's not a worse taste in the right or left group. Just a bit different.

I have on order from Vaneli's a bottomless portafilter. When it arrives I will try the two extremes of tamps. #30 and a light kiss of a tamp.

[narc]

This morning using the new "Newd" portafilter I progressively increased the tamp pressure and fineness of grind. I know two variables make the following observation semi- meaningless. Actually 3 variables. I'm pretty sure the dose was increasing with each shot. The element I left constant was the clearance between the coffee and lip of the basket. The machine was the MicroCasa a Leva(MCaL). 1st shot was a sinker. Not sure if it was a dose, distribution, tamp or all the factors. Uneven extraction. 2nd shot, 1/2notch on the MazzerMini finer, little heavier tamp. Looked good extracting. In terms of taste subpar. For me another sinker. 3rd shot, 1/2 notch finer and harder tamp. Looked good extracting. Taste acceptable. 4th shot, full notch finer and full #30 tamp. Shot extracted how I was hoping for. 3-4 sec preinfusion, drops appeared 2-3 seconds after releasing lever, nice looking extraction. Taste for this 50:50 blend of India Mallali:Mexico Oxaca was very acceptable. More intense flavors, darker & thicker crema. I think I'm back to a heavy tamp on MCaL. Starting to feel little schizo when it comes to pulling shots.

Prior to the MCal shots I pulled couple light tamp shots with the same blend on the Ponte Vecchio Lusso (PVL). The grinder was set at the MCaL pull #3 with a light tamp. Both shots were acceptable. The PVL characteristic heavy, thick crema and sweeter bias obscuring some of the subtle flavors pulled on the MCaL.

Maybe I need to change the headspace on the MCaL to the 6mm space I leave on the PVL for a lighter tamp on the MCaL. I'm really confusing myself. Too much thought. Paralysis by analysis is setting in.

[AndyS]

The boiler pstat is set at 1.0 +/- 0.05 bars. So the maximum pressure at preinfusion would be ~29.4 psi(1atm + 1.05 bars).

No, actually the max pressure on your puck at preinfusion is ~15.2 psi (1.05 bar). Atmospheric pressure is present both above and below the puck, so it cancels out.

Considering the linear water flow that hits the puck initially at a low pressure maxing to the 1.05 Bars would not the puck be basically "tamped" by the water pressure to ~30pounds?

No again, 1.05 bars on a 58mm diameter puck is equivalent to about a 60 lb tamp (~15 psi x ~4 sq inches).

[AndyS]

I just find this whole subject pretty funny because with my coffee, my machine and my technique, tamping pressure makes almost no difference in shot timing.

In other words, I've repeatedly compared shots tamped at 10 lbs with shots tamped at 60 lbs and found little or no difference. When people say they instinctively "correct" a grind that's a little too coarse by tamping harder, I just scratch my head, knowing it would make no difference on my setup.

Does it have to do with the fact that I dose low (13-14g) in a double basket? Is it the line pressure preinfusion that I use? Is it the fact that I am too dumb to notice the difference? I'm not sure, but it's an endless source of amusement for me to read all the fuss made about tamp pressure.

[HB]

Does it have to do with the fact that I dose low (13-14g) in a double basket? Is it the line pressure preinfusion that I use? Is it the fact that I am too dumb to notice the difference? I'm not sure, but it's an endless source of amusement for me to read all the fuss made about tamp pressure.

Probably the first two are true. I have no way of proving it, but my WAG for pump extractions is that the tamp pressure affects the efficacy of the initial wetting and thereby impacts the puck expansion. For multiple lever pulls, I assume the puck is almost a slurry between strokes and is then re-compacted by the force of the water itself. Anyone got a transparent basket and some dyes to confirm?

[peacecup]

Andy - can you choke your machine with a fine grind? Try keeping a good 30# tamp, and tightening up the grind until you completely choke the machine. Then use the same grind and don't tamp at all, just level it with the tamper (you will probably need to adjust the dose to leave approx. the same headspace after tamping/leveling). Does the machine still choke using the same grind fineness but no tamp?

PC

[grong]

I just find this whole subject pretty funny because with my coffee, my machine and my technique, tamping pressure makes almost no difference in shot timing.

On my percolator, I mean espresso set-up, varying tamp pressure with the grind remaining constant has a noticeable effect on the flow rate and final product. I can slow it down or speed it up with varying pressure. I imagine that I fine tune the tamping pressure minutely to create an ideal extraction. This greatly enhances the entire experience. Slower shots are heavier and more syrupy, faster pulls illuminate more elaborately the subtle flavor distinctions.

For multiple lever pulls, I assume the puck is almost a slurry between strokes and is then re-compacted by the force of the water itself. Anyone got a transparent basket and some dyes to confirm?

In my imagination I apply the Heisenberg principle and the puck remains in perfect formation during multiple pulls, which is why, I think, I think the espresso tastes so good. I like the double pull easily as much as the single pull, though they do taste different, the single being fluffier and purer, the double more daring and worldly.

[AndyS]

Andy - can you choke your machine with a fine grind? Try keeping a good 30# tamp, and tightening up the grind until you completely choke the machine. Then use the same grind and don't tamp at all, just level it with the tamper (you will probably need to adjust the dose to leave approx. the same headspace after tamping/leveling).

Well sure I can choke it with a fine enough grind.

As far as your test goes, I'm with you up until you adjust the dose. One can't test the effect of differing tamps if the dose is also changed.

[peacecup]

Well Andy, you don't need to adjust the dose. Just grind down until you choke the machine with a standard tamp pressure, then use the same grind but don't tamp. The headspace will be less is the point.

RE: Dan's assertion that the puck becomes a slurry during multiple pulls, this is not always so. With moderate (~10#) tamp on the Ponte Vecchio the puck will remain entirely intact during two or more pulls if the dose if the grind is relatively coarse and the basket full (but not necessarily touching the screen). I can say this for certain because there is no way that the solid pucks I eject from my double basket could be compacted by the piston pressure. I see I need to post some photos of these.

And this brings us back to one of the points of the thread, and is relevant to Andy's original question. I initially went with a coarser grind/harder tamp because I wanted to use a very full (but not touching) double basket (i.e. maximum dose) on the PV. This comes out around 15g, maybe more. If I fill the basket that full with a finer grind it will always choke the machine, so I needed to back off. So one reason to use the coarser grind is to get the maximum dose possible, and therefore a greater volume of espresso per shot. I've since reduced my dose requirement, so a finer grind is possible.

I do plan on running some informal taste tests ASAP between the two.

PC

PS, Andy, I do know Richard C, but mostly by reputation. He is a tireless advocate for preserving the last great wilderness in North America, the Tongass National Forest.

['Q']

It seems to me that a non-compacted mass (ie light tamp) would be very unstable when first exposed to the brew water, and that the surface layers at least would be disturbed. I've always assumed that this would lead to channels being formed in the "puck", causing an uneven extraction. A firmly-tamped a polished surface would act as a buffer, allowing the puck to remain intact while water slowly infuses it. Think of an earthen dam being hit by water, for example, vs. the same pile of earth that was not compacted.

I don't fully agree with this theory. IF the "puck" is evenly distributed and the water pressure evenly applied, there should be little-to-no disturbance to the puck regardless of the compactness of the grounds (so long as there is constant forward force on the puck). The basket is the barrier and the grounds are held back by it. As more pressure is applied, the puck will become more compact against the basket screen and thus provide more resistance against the flow (think leaves packed in a drainage grate). You should get channeling if there is a void of grounds in the puck and/or jet(s) of water against it, otherwise it should stay intact. If there are voids, it would also make sense to me that a lesser tamped puck and slower ramp-up of force would allow the voids to fill-in and basically somewhat heal, resulting in a better overall extraction. I believe I read a thread on here where it was brought up that increasing the force on the lever tended to slow the extraction and that makes sense with the water force compressing/compacting the puck.

I don't use a lever machine (yet) but lately I've been experimenting with a little bit different technique: Grind enough to cover the bottom of the basket, very lightly tamp with a smaller tamper that fits the bottom of the basket, finish grinding to fill the basket and lightly tamp the top. The jury is still out...

[grong]

As more pressure is applied, the puck will become more compact against the basket screen and thus provide more resistance against the flow (think leaves packed in a drainage grate).

Also, as with dry leaves to wet, the wetted coffee grounds swell together in the confines of the basket, filling voids, then are compressed with water pressure. (I'm no scientist.)

With a hard tamp, which I of course think makes great espresso, the outside puck surfaces are surely tamped more compact than the interior.

[timo888]

...I've repeatedly compared shots tamped at 10 lbs with shots tamped at 60 lbs and found little or no difference.

By 'light tamp', I am talking about 0-300g, i.e. less than 1 pound ... not 10 pounds. The very light tamp just creates minimal headroom, to keep the shower-screen clean.



Regards
Timo

[HB]

Dan's assertion that the puck becomes a slurry during multiple pulls, this is not always so. With moderate (~10#) tamp on the Ponte Vecchio the puck will remain entirely intact during two or more pulls if the dose if the grind is relatively coarse and the basket full (but not necessarily touching the screen).

For the record, I am not asserting anything. I assume the puck has slurry characteristics because the vacuum created by the upstroke doesn't produce catastrophic channeling as I would have expected for a firm puck. An assumption is all I can offer since I have not measured or observed the process directly.

I can say this for certain because there is no way that the solid pucks I eject from my double basket could be compacted by the piston pressure.

That sounds like an assertion of an assumption to me, but I'm nitpicking. From this point forward I will focus on the end results in the cup and not "puckology."

[peacecup]

This is all very interesting in theory, but as Dan notes, it is results in the cup that count. That said, it would be satisfying to understand the mechanisms that determine results. In this thread I am encouraging fellow HB'ers to experiment with different techniques, to try to shed some light on how tamp pressure (and related changes in grind and dose) effect flavor, crema, shot volume, or whatever else they consider an important result. For example, we've seen timo expound on the virtues of the "tampless tamp". I would like him to try dialing in a hard tamp, then have him describe HOW the results in the cup differ.

Of course, it is an assumption that a firmly-tamped puck will stay intact, since I cannot actually see it. And it is somewhat trivial "puckology" on one level. On another level, however, understanding what happens in the basket can increase our ability to predict what comes out the other end. This is one reason naked PF's are so popular, because they give us a glimpse, at least, of what we can't see inside.

After 20 years of schooling and working, I am slowly beginning to consider myself a scientist. I like to uncover the mechanisms that underlie patterns that I observe. One simple example is "What did I do to those coffee grinds to make the espresso sweet (or bitter!)?".

One of the reasons I love espresso so much is that it is the interaction of a few simple physical factors (pressure, temperature, hydrodynamic properties), can make one of the "Seeds of the Earth" even more pleasurable than it is when simply boiled.

BTW, this AM's cappa was set to a coarser grind/harder tamp than I have been using lately, and it was exquisite. More food for thought, until have some time this weekend to run some simple taste tests...

PC

[grong]

For the record, I am not asserting anything. I assume the puck has slurry characteristics because the vacuum created by the upstroke doesn't produce catastrophic channeling as I would have expected for a firm puck.

As a non-scientist, I have been pondering the vacuum phenomenon in the piston chamber, and just how disruptive or significant it could be. With the Lusso, let's assume pressure on the saturated puck. The arm is then lowered to raise the piston, creating the vacuum whose forces increase as the piston lifts—but the piston on this machine lifts only about 5/8 inch in total. Methodical movements would limit the potential shock effect. And somewhere before that time water pressure from the boiler fills the vacuum.

['Q']

In thinking about this thread in the shower this morning (I do some of my best thinking in the shower ) I came to a couple more theoretical conclusions.

1) Assuming acceptable grind, the effect of tamp pressure is probably parabolic with respect to flow. A variance in tamp between 0# and (I would guess) about 10# affecting flow very little, if any. Tamps between 10# and roughly 40# would have greatest effect. And variances above 40# (within reason) would again be little. This also stands to reason that tamp pressure at either end of the scale would be easiest to maintain consistency.

2) Grind fineness and distribution would have greatest influence on flow rate at the no-tamp to light-tamp end of the scale.

I'm not advocating anything, just thinking aloud here. It does seem reasonable to me that one would be most consistent (but not necessarily the best tasting) by grinding coarser and tamping hard. Of course it seems that the best tastes come from that fine balance between grind, distribution, tamp, flow, temperature, etc, etc, et... (oh, and ones personal taste) so I really doubt there will ever be that magic answer.

[timo888]

... I can say this for certain because there is no way that the solid pucks I eject from my double basket could be compacted by the piston pressure. I see I need to post some photos of these.
...
PS, Andy, I do know Richard C, but mostly by reputation. He is a tireless advocate for preserving the last great wilderness in North America, the Tongass National Forest.

I know peacecup's pucks only by reputation, but I do often get firm pucks from the Cremina using no tamp whatsoever. I recall the edges of the Lusso's spent pucks being more Heraclitean. Differences in brew pressure are likely to be a major factor here, as well as dose to water-draw ratios.

Regards
Timo

[grong]

I have a Lusso. I just prepared two baskets with a blend of beans representing two Brazils, one Nicaraguan, and one Ethiopian Sidamo, roasted FC+, aged four days.

For basket No.1 I ground to my standard for a very light tamp. For the next basket, No. 2, I ground one notch coarser (Macap M4), and prepared this with a 30 pound tamp. I pulled basket No. 1, tasted and enjoyed a full-bodied cup with delicate chocolate flavors and an overall rounded profile. Then I pulled basket No. 2—more effervescent body, and more biting chocolate, overall less balanced and smooth than No. 1. For both pulls, flow rates and volume were very similar. Lurking variables include temperature, moon and stars—no pretense of a scientific method, but representative of what happens at my espresso bar.

Over time, the light tamp works well for me, my blends and machine, and my tastes. It is fun to taste test both tamping methods. Every home barista is sure to find out what works best to produce the most pleasing cup.

[AndyS]

IF the "puck" is evenly distributed and the water pressure evenly applied, there should be little-to-no disturbance to the puck regardless of the compactness of the grounds

That's a very big IF.

(1) The puck is never perfectly evenly distributed.
(2) Since water flow into the grouphead commences as single droplets, it is NOT evenly applied at the beginning, which is the most crucial time.