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Thread: Why tamping doesnt matter as much as you think

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    Why tamping doesnt matter as much as you think

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    The magical 15 kg of "force/pressure" has often been used as a benchmark for tamping in industry. It gives baristas a baseline to work from – 15 kg of downward "force" is merely a trade off between the compactness of the bed of coffee and preventing RSI (repetitive strain injury) for baristas tamping hundreds of group handles a day. As long as you are consistent, it does not matter how hard you tamp.

    The reasoning is this: tamping harder or softer will have negligible impact on an extraction flow rate once the coffee bed has been tamped with sufficient pressure to remove any air pockets between coffee grinds. 9 bar of extraction pressure is 16 times greater* than the pressure of a 15 kg tamp. Tamping pressure is immediately alleviated during the period when the dry coffee is wetted and once the extraction is in full swing will always be much less than pump pressure.

    So when someone says tamp harder to slow down an extraction, I call bs!* ::)

    Discuss, debate, theorise..... 8-)

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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 0E383B392E3838241828232424274B0 link=1332222307/0#0 date=1332222307
    So when someone says tamp harder to slow down an extraction, I call bs!
    Two thought provoking posts back to back! Thanks Dave.* 8-)

    Yep- I totally agree. In fact its amazing to look at how bad a tamp can be and yet still be normalised by the machine (given correct dose). This will be a debate well worth reading!

    Chris

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    Senior Member specialpants's Avatar
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    Re: Why tamping doesnt matter as much as you think

    I think its a give and take.

    If youre not going to tamp hard, then its better if you use more coffee and/or a finer grind. Conversely If you are going to tamp as hard as you can, then its better if you use less coffee and/or coarser grind.

    I use to tamp pretty hard because a domestic course I did a few years back (2006 at Danes / the gourmet coffee institute) said 15kg was the sweet spot. I knew the trainer and he made great coffee and won competitions etc.* so I naturally took this on board.

    It wasn’t until last year I made some changes to how I make coffee. The owner of the cafe invited me behind the counter and watched me make my coffee. He commented on the amount of pressure I used to tamp, and recommended that I grind finer and use less force. He also said it wasn’t important to have a dry and rock hard puck once the extraction was finished (which is something I also use to aim for – I was told it should have an imprint of the shower screen).

    Both Baristas make an excellent cup of coffee and yet both have different techniques. It just goes to show that either way works.

    I’ve gone for the middle ground and use 3~5kgs (maybe even less!) of force. My pucks now have a slight imprint of the shower screen and hold their shape when knocked out. They are somewhat firm, but not rock hard as they use to be.

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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 1310050309010C10010E1413600 link=1332222307/2#2 date=1332237329
    My pucks now have a slight imprint of the shower screen and hold their shape when knocked out. They are somewhat firm, but not rock hard as they use to be.
    To the uninitiated this could really read like a health forum.
    Cheers
    BOSW
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    Senior Member Jono_Willmer's Avatar
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    Re: Why tamping doesnt matter as much as you think

    Since getting the duetto and kony ive played around alot more with different techniques. What I have found though is if I get the dose weight right (vst 18g basket) i dont have to worry about tamping pressure, i just polish and extract. I have compared this to a 15kg tamp same dose and grind and extraction is the same.

    I think Ive seen a Scott C you tube video where he explains this, though it may have been someone else sorry.

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    Re: Why tamping doesnt matter as much as you think

    Espresso School,
    Have you ever tried an experiment where you try changing only the tamping weight?
    I have and it makes a huge difference. You can vary from a restricted pour to a fast pour at the extremes.

    I expect a consistent grind / tamp is what is important, grind fine and tamp light or vice versa.

    Lee

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    Senior Member dski's Avatar
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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 2E2F212E2330272C420 link=1332222307/5#5 date=1332240229
    Espresso School,
    Have you ever tried an experiment where you try changing only the tamping weight?
    I have and it makes a huge difference. You can vary from a restricted pour to a fast pour at the extremes.

    I disagree. Tamp can effect pour time but the amount of variation is negligable compared to grind. As others have said, I dont think dose can be underestimated either.

    I tend to think that a level tamp is more important than the actual pressure used. What do you guys reckon?


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    Senior Member Jono_Willmer's Avatar
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    Re: Why tamping doesnt matter as much as you think

    "I tend to think that a level tamp is more important than the actual pressure used. What do you guys reckon?"

    I agree level tamp, dose and grind size seem to be what has the greatest effect on the results for me.

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    Re: Why tamping doesnt matter as much as you think

    Heres another variable: preinfusion

    Without preinfusion my tamp does seem to matter a bit more, tamp too light and I occasionally get some chanelling. Tamping firmly fixes it.
    With pre-infusion, tamp pressure makes a lot less of a difference, as long as its distributed evenly.

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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 55545A55584B5C57390 link=1332222307/5#5 date=1332240229
    Espresso School,
    Have you ever tried an experiment where you try changing only the tamping weight?
    I have and it makes a huge difference. You can vary from a restricted pour to a fast pour at the extremes.

    I expect a consistent grind / tamp is what is important, grind fine and tamp light or vice versa.

    Lee
    Hi Lee,

    Quote Originally Posted by 7C4A494B5C4A4A566A5A51565655390 link=1332222307/0#0 date=1332222307
    The reasoning is this: tamping harder or softer will have negligible impact on an extraction flow rate once the coffee bed has been tamped with sufficient pressure to remove any air pockets between coffee grinds....Tamping pressure is immediately alleviated during the period when the dry coffee is wetted and once the extraction is in full swing will always be much less than pump pressure.
    So in summary, if you tamp like a gorilla, its going to have negligible effect on the overall extraction. What you will do though is cause the infusion time to be longer by a few seconds at most. The key thing here is that you have tamped sufficiently hard enough to remove any pockets of air between grinds.


    Good discussion so far! 8-)

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    Re: Why tamping doesnt matter as much as you think

    Heres the mathematics behind it all.





    Assuming a 15 kg tamp.



    We know an espresso machine pump operates typically at 9 bar.

    0.56 bar of tamping pressure is dwarfed by 9 bar of pump/brewing pressure. To put it in simpler terms, pump pressure is 16 times greater than the pressure of a 15 kg tamp in a 58 mm filter basket!


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    Re: Why tamping doesnt matter as much as you think

    One problem with that analysis. You are assuming that the pressure drop over your puck is the full 9 bar. I dont think that will be the case. Most of the pressure will likely be dissipated once the water passes through the puck.

    The actual pressure drop over the puck depends on lots of factors (particle size, void space, particle surface properties, fluid viscosity...) and would be very hard to calculate (and it would be hard to make reasonable assumptions of those factors).

    I think it would be more relevant to consider/discuss what happens to the puck when wetted, and whether this varies depending on tamp pressure (which will tell you if dP over the puck will vary depending on tamp pressure).

    My second crack.

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    Re: Why tamping doesnt matter as much as you think

    If you find that a very hard tamp or a very light tamp is necessary, you are most likely compensating for some other problem which should be addressed.

    What force to use? Just tamp hard without getting crazy about it. Anything from about 14-16Kg (30-35 pounds) and up will do fine. You can test that using a scale. You should find that once you hit that level of force that there is virtually no compacting of the coffee as you increase the force.

    Consistency is important, but anything between about 14-27Kg (30-60 pounds) will be fine.

    As far as comparing water force to the force applied to your tamper, this is apples and oranges unless the water is in the form of ice. ;) Water delivery at the beginning of the extraction is not applied evenly, and water is a solvent. Depending on how the pressure is applied (slow infusion as from an E-61 or rudely as in a Silvia) can do all sorts of things to the coffee that make this comparison not very accurate at all.. IMO.

    Tamp level, tamp with a consistent force, use a proper-fitting tamper, and never tap the sides of the portafilter after tamping. Beyond that, dont worry about it.

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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 112724263127273B07373C3B3B38540 link=1332222307/0#0 date=1332222307
    So when someone says tamp harder to slow down an extraction, I call bs!*
    I suspect that applying a simplistic, quasi-scientific analysis to the process has led to this assumption.

    Its certainly not as simple as comparing the force applied by the pump with the force of the tamping.

    Empirically, I know I can compensate for minor differences in the grinder setting with minor changes in the tamp pressure. I have an adjustable, clicking tamper so I know exactly what tamp pressure I am applying and I use a spring lever machine so application of pressure is gentle and consistent.

    As an example if I am making a few coffees and the grind is a little bit fine, i will back off the adjustable tamper slightly and I will see a direct increase in flow rate of the pour - and vice versa if its a bit coarse.

    I will choose to adjust the tamp rather than the grind if I am in a hurry and using the Pharos as its a bit quicker to adjust the tamper.

    Quote Originally Posted by 06353A302D0B137A540 link=1332222307/12#12 date=1332265122
    Tamp level, tamp with a consistent force, use a proper-fitting tamper, and never tap the sides of the portafilter after tamping. Beyond that, dont worry about it.
    Exactly!

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    Re: Why tamping doesnt matter as much as you think

    Ive had varying feedback on this subject (and that of fitted tampers) over the years. I put it down to different machines. Maybe its pre-infusion, not sure. But certainly low to mid-end machines seem to give much worse results with a loose tamper or no tamper at all, compared to top-end machines. Tamp pressure would be a subset of this argument. Thats of course overlooking the mess factor that has to be cleaned up by not tamping and the problems if you dont clean it up.

    Greg

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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 6B6E7777767A751B0 link=1332222307/14#14 date=1332290391
    Ive had varying feedback on this subject... But certainly low to mid-end machines seem to give much worse results with a loose tamper or no tamper at all, compared to top-end machines. ..Greg
    I do not think that this is necessarily the only factor. Low end machines tend to be owned by inexperienced users who use low-end grinders and are more likely to be using low-quality, stale coffee. They try all sorts of tamping technique and when they finally get two in a row that doesnt spray the counter top they share their "perfect technique to tamp with machine X" and the word spreads.

    I have made some very acceptable (albeit unremarkable) espresso using a thermoblock Krups espresso machine but paired with a quality grinder and fresh, properly-roasted beans.. I even used a little skill as well. ;)

    Invoking the redundancy factor, if you find you need a particularly high or particularly low tamp force, there is most likely another problem the user is compensating for. (Lever machines may be an exception as they seem to like fine grind and low tamp force, from what I hear.)

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    Re: Why tamping doesnt matter as much as you think

    I have found that tamping force doesnt matter as much as some think, but mainly due to the difficulty in getting consistent dose amounts....for me the variations in dose amounts easily caused more variations in pour and taste than the tamping force, until I got some digital scales, now things are more consistent. Also for limited volume home use the variations in humidity from one day to the next can have just as much affect as anything else, which I know can be different in a commercial environment where you are trying to make many drinks consistently during the course of a day.
    Finally, I also have found that a good tamper does help at least as much as anything else.

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    Re: Why tamping doesnt matter as much as you think

    one error in the analysis is that is that the full 9 bars of pressure doesnt actually compress the puck.

    Not to mention that because there is water flowing out, and at force (around 3 bar which is line pressure) the actual pressure being exerted on the puck is a lot less than the full 9 bar.

    But yes the theory still stands.

    Heck the whole 30 second extraction rule doesnt matter as well. There is no valid reason why if you run the grind fine enough you cant run a shot in 10 seconds and get the same quality of espresso. I certainly can.

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    Re: Why tamping doesnt matter as much as you think

    Autti,
    A properly adjusted machine is 9 bar at the group, not the pump. So line pressure is moot. It is also 9 bar whilst extracting, so yes the coffee does get the full 9 bar.

    I dont believe that 10 sec claim at all - its a gusher and wont taste as good as it could at all.

    And finer grind = longer pour, not shorter. So a few errors there.
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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 07362138393E35382E570 link=1332222307/18#18 date=1334007802
    I dont believe that 10 sec claim at all - its a gusher and wont taste as good as it could at all.
    I could not agree more with this, I have never been able to get anywhere near as good pour in 10s as 25-30s. I have even become such a snob that I sink it if it is a 10s pour because after tasting several when trying to get my grind, volume and tamp correct I learned that it just didnt taste good enough.

    As far as tamp force goes - and I am far from an expert... I couldnt agree more with Randy. I just aim at a good consistent and not overly firm tamp (when i was first trying to get my shots right I would use gorilla force) that is level with the right grind and dose.

    I still want a custom Pullman barista tamper though.... ::)

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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 0534233A3B3C373A2C550 link=1332222307/18#18 date=1334007802
    Autti,
    A properly adjusted machine is 9 bar at the group, not the pump. So line pressure is moot. It is also 9 bar whilst extracting, so yes the coffee does get the full 9 bar.
    Sorry not the best wording. What i meant is that it doesnt actually exert 9 bars of pressure as there is water flowing through. Otherwise if you add the forces you would have 9 bar plus 1-2 bar of the force of the shot water which equals 10-11 bar, more than the pump is pushing. See how it works?

    I used line pressure as a shot flows around that rate, slower at the start obviously.

    My point is that saying a puck is being compressed by 9 bars of pressure is simply false, its a lot less simply because a) water is flowing through it and b) the puck is 100% resistant.

    And finer grind = longer pour, not shorter. So a few errors there.
    Finer grind + light tamp + big baskets. Easily achievable.

    Have a play around.

    What you should remember is the 15kg 30second rule is just a formula, you can change parts and achieve the same result which is a % of dissolved coffee.
    Saying that 15kg and 30s will get the best results is erroneous, there are plenty of different ways to achieve good espresso while deviating, they just arent as well known or used.

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    TC
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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 231716160B620 link=1332222307/20#20 date=1334012420
    Sorry not the best wording. What i meant is that it doesnt actually exert 9 bars of pressure as there is water flowing through. Otherwise if you add the forces you would have 9 bar plus 1-2 bar of the force of the shot water which equals 10-11 bar, more than the pump is pushing. See how it works?
    Yes and no. Many operations will use a Scace II device to set pressure. This will replicate flow during the shot.

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    Re: Why tamping doesnt matter as much as you think

    What do you mean replicate flow during the shot?

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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 053130302D440 link=1332222307/22#22 date=1334115527
    What do you mean replicate flow during the shot?
    replicate = imitate or copy
    flow = pour rate
    during = whilst the event is occuring
    pour = what ends up in the cup

    Might be worth googling Scace II* :-?

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    Coffee+carbon=heaven Mono's Avatar
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    Re: Why tamping doesnt matter as much as you think

    I was at a bakery/cafe over the Easter break and we all ordered coffees etc. I got a Cafe Latte and I watched the young girl making it. Ground into the basket, tapped once, leveled/tamped with her palm and into the machine it went. Thoughts went through me head reminding me why I do not buy coffee when out as I am generally underwhelmed.* I do understand that milk will hide a lot but it was quite ok and I was pleasantly suprised.

    BeanBay

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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 63565B5C68745851515252370 link=1332222307/23#23 date=1334116880
    Quote Originally Posted by 053130302D440 link=1332222307/22#22 date=1334115527
    What do you mean replicate flow during the shot?
    replicate = imitate or copy
    flow = pour rate
    during = whilst the event is occuring
    pour = what ends up in the cup

    Might be worth googling Scace II* :-?
    Ok i had a look.

    It still doesnt address that facts that a) a coffee bed isnt completely resistant and b) water is flowing out of the coffee bed and therefore the force isnt all compression.

    Ergo there cannot be full pump force compression on a coffee puck.

    Although the equation gets a lot more complex when you consider that the basket has a level of resistance as well which would also alter the force on the puck.

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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 695D5C5C41280 link=1332222307/25#25 date=1334133445
    a) a coffee bed isnt completely resistant and b) water is flowing out of the coffee bed
    I understood that these were exactly the properties that Mr Scace designed his device to replicate - even down to retaining the same amount of water as is typically absorbed by the puck. His device wouldnt deserve its almost mythical reputation if it didnt do a good job replicating all the dominant factors.

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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 4F7B7A7A670E0 link=1332222307/20#20 date=1334012420
    My point is that saying a puck is being compressed by 9 bars of pressure is simply false
    No its not. If your over-pressure valve is set to release pressure at 9 bar (as mine is), and the valve is open during the shot (as it is on my machine - as I can see the water bypass emptying back to the tank), then there must be 9 bar at the coffee puck. If there wasnt 9 bar at the puck the over-pressure valve wouldnt have opened.

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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 0E2520204C0 link=1332222307/27#27 date=1334201918
    Quote Originally Posted by 4F7B7A7A670E0 link=1332222307/20#20 date=1334012420
    My point is that saying a puck is being compressed by 9 bars of pressure is simply false
    No its not. If your over-pressure valve is set to release pressure at 9 bar (as mine is), and the valve is open during the shot (as it is on my machine - as I can see the water bypass emptying back to the tank), then there must be 9 bar at the coffee puck. If there wasnt 9 bar at the puck the over-pressure valve wouldnt have opened.
    I not saying there isnt 9 bar of pressure.

    Im saying that the 9 bar of water pressure isnt COMPRESSING the puck with 9 bars. I certainly agree that there is 9 bars of water pressure going through the coffee, but that is not the same as a 9bar tamp.

    I will test this on my drill press with a load sensor.

    I will bet you that 9bar tamp will compress the coffee a lot more than 9 bar water pressure. Ergo you cannot equate water pressure to tamp pressure directly.

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    Re: Why tamping doesnt matter as much as you think

    and.....It will all anount to about 2/10 of nothing difference.

    In the meantime, Ill have a coffee ::)

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    Re: Why tamping doesnt matter as much as you think

    i have stock BES900 tamp, i just tamp to flatten the coffee so it slots in, and not spilling everywhere...

    I dont really goto town and try to fuse atoms in the basket.

    Light press, squared off, nice and clean. ready to roll

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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 1125242439500 link=1332222307/28#28 date=1334206431
    Im saying that the 9 bar of water pressure isnt COMPRESSING the puck with 9 bars. I certainly agree that there is 9 bars of water pressure going through the coffee, but that is not the same as a 9bar tamp.
    Hi Autti - I think we are all arguing the same thing... its just that some imprecise use of language is obfuscating this :)

    As Randy noted early on, its "apples and oranges unless the water is in the form of ice."

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    Re: Why tamping doesnt matter as much as you think

    Noob here - but with my PV Lusso & a fine grind, I can get the flow rate to vary from a thin stream right through to 1 drip per 5 seconds only by varying how hard I tamp. So I do think it makes a big difference and when I drink those shots that took 2-3 minutes to pour you can certainly taste it.
    Im trying to get a feeling for what happens as I tamp - at a certain point you can almost feel the coffee lock down and stop compressing and Im finding best results if I stop just short of that. Or it could be my imagination...

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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 072524254A0 link=1332222307/24#24 date=1334119290
    leveled/tamped with her palm
    I hope her hands were clean.

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    Re: Why tamping doesnt matter as much as you think

    One notch on my grinder tends to be the difference between good pour and staller. Id only use a finer setting for supermarket beans. So I mostly adjust the tamp and dose. If I dose a little more and tamp harder, I maintain a good flow rate after my beans have gone stale. If youre tamping down hard but not dosing anymore, so that its tamped lower in the basket, it wont make that much difference because its going to expand upwards into that space and undo much of the harder tamp.

  36. #36
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    Re: Why tamping doesnt matter as much as you think

    Warning: This will be a short (or long) lecture.

    As a mineral processing engineers, I deal with a few different process equipment and one of which is filters. Filters works in the principal of pressure difference. The pressure difference is created by applying a vacuum or a pressure force on one side of the filter medium.

    There are two types of filters:
    1. Vacuum filters: The liquid is pulled through (under vacuum) the filter medium, leaving the solids on the
    other side (filter cake)

    2. Pressure filters: The liquid is pushed through (under pressure) the filter medium, leaving the solids on the
    other side (filter cake)

    I think we all agree that our coffee machines are pressure filter so Ill discuss pressure filter instead.

    Key parameters for filters are:
    -
    Particle size
    - Filter medium
    - Feed slurry density
    - Pressure difference
    - Rate of filtration

    Particle size and filter medium is inter-related, and we all know that the our filter basket is fine enough to hold the ground coffee and let the brewed liquid to pass through (the effect of these on filtration rate will be discussed later). Well ignore feed slurry density because its not a factor for our discussion (all use water and ground coffee as the slurry). Pressure difference is created by the espresso machines specific.

    So this is what we were interested in: rate of filtration (or pouring). There are several factors affecting rate:

    1. Resistance of filter medium (basket): is dependent on the size of pores and is impacted by how clean or dirty the filter medium is. when the fine solid particles embedded within the pores of filters,it makes difficult for the liquid to move through the medium. The filter medium resistance is therefore combination of resistance of the filter medium and the embedded particles.

    2. Resistance of filter cake (puck): is dependent upon the filter cake thickness and the amount of voidage (spaces between the particles) in the cake.

    When filtration commences, the filter cake resistance will be zero as initially there will be no cake build-up (i.e. the cake depth will be zero). As filtration proceeds and the cake depth increases, the cake resistance will increase and become the
    predominant source of resistance.

    The voidage or spaces within a cake is related to the size distribution of the solid particles and the particle size. The finer the solid particles, the smaller the spaces between the particles and the higher the cake resistance (due to the particles being packed closer together).

    The higher the resistance, the slower is the rate of pouring. If resistance is too high the moisture level in the final filter cake will increase (wet puck).

    Tamping too hard together with too fine grind size and/or too much ground coffee on filter results in dripping pouring to none at all (Ive tried this).

    In conclusion, tamping does mater up to certain point; it minimise the time required for filter cake formation by pressing and compacting (forced formation) results in evenly distributed and higher resistance initially. Another factors are more important however, such as grind size, height of filter cake (consistent dosing) and pressure difference.

    Open for discussion :)

    HH

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    Re: Why tamping doesnt matter as much as you think

    I dont understand why you would ignore slurry density when it is a dynamic medium and will behave differently at different stages of the extraction.

  38. #38
    harison.harison
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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 1D3C3737302A590 link=1332222307/36#36 date=1338595717
    I dont understand why you would ignore slurry density when it is a dynamic medium and will behave differently at different stages of the extraction.
    Because that itself may create separate forum and its not something that we can control (maybe im wrong with this). But i know that density is mass per volume and as temperature increases mass stay the same and volume increases ie. density decreases. However up to certain point, density inside the filter will remain constant due to limited volume, so liquid has to escape somewhere and thus maintain the same density. If water doesnt escape, then it will build up pressure and may cause explosion.

  39. #39
    Senior Member Yelta's Avatar
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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 21283B203A26276721283B203A2627490 link=1332222307/35#35 date=1338595008
    Warning: This will be a short (or long) lecture.
    Crikey HH, you obviously have waaaay too much time on your hands.* :)

  40. #40
    Senior Member Dennis's Avatar
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    Re: Why tamping doesnt matter as much as you think

    HH, I think you might be approaching the topic as though there are constants involved. While there are some, one coffee will behave quite differently to another.

    Suggest you take a close look at the way most group heads are designed and how they resolve the possibility of explosions. Also recommend to you "espresso coffee the science of quality" by Illy. ;)

  41. #41
    harison.harison
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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 1D3C3737302A590 link=1332222307/39#39 date=1338598760
    HH, I think you might be approaching the topic as though there are constants involved. While there are some, one coffee will behave quite differently to another.

    Suggest you take a close look at the way most group heads are designed and how they resolve the possibility of explosions. Also recommend to you "espresso coffee the science of quality" by Illy.* ;)
    You are absolutely correct, I am just approaching it by bird view, of course there are deeper way to look at it. After all, I am still learning. Will check on the book. Thanks!

    Quote Originally Posted by 003C352D38590 link=1332222307/38#38 date=1338598557
    Quote Originally Posted by 21283B203A26276721283B203A2627490 link=1332222307/35#35 date=1338595008
    Warning: This will be a short (or long) lecture.
    Crikey HH, you obviously have waaaay too much time on your hands.* :)
    Cant help it, lazy Saturday and reading on CS forum. Cant get any better!

  42. #42
    Senior Member Dennis's Avatar
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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 767F6C776D717030767F6C776D71701E0 link=1332222307/40#40 date=1338599355
    Will check on the book
    I think youll love it!!

  43. #43
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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 77565D5D5A40330 link=1332222307/41#41 date=1338600375
    Quote Originally Posted by 767F6C776D717030767F6C776D71701E0 link=1332222307/40#40 date=1338599355
    Will check on the book
    I think youll love it!!
    Hey thanks for the recommendation Dennis. Was just thinking of buying the ebook yesterday, and it looks like youve convinced me.

    Now off to do some "light" reading ;D

  44. #44
    Senior Member Yelta's Avatar
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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 4B42514A504C4D0D4B42514A504C4D230 link=1332222307/40#40 date=1338599355
    Cant help it, lazy Saturday and reading on CS forum. Cant get any better!
    Fair nuff. :)

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    Re: Why tamping doesnt matter as much as you think

    Quote Originally Posted by 1024252538510 link=1332222307/28#28 date=1334206431
    Quote Originally Posted by 0E2520204C0 link=1332222307/27#27 date=1334201918
    Quote Originally Posted by 4F7B7A7A670E0 link=1332222307/20#20 date=1334012420
    My point is that saying a puck is being compressed by 9 bars of pressure is simply false
    No its not. If your over-pressure valve is set to release pressure at 9 bar (as mine is), and the valve is open during the shot (as it is on my machine - as I can see the water bypass emptying back to the tank), then there must be 9 bar at the coffee puck. If there wasnt 9 bar at the puck the over-pressure valve wouldnt have opened.
    I not saying there isnt 9 bar of pressure.

    Im saying that the 9 bar of water pressure isnt COMPRESSING the puck with 9 bars. I certainly agree that there is 9 bars of water pressure going through the coffee, but that is not the same as a 9bar tamp.

    I will test this on my drill press with a load sensor.

    I will bet you that 9bar tamp will compress the coffee a lot more than 9 bar water pressure. Ergo you cannot equate water pressure to tamp pressure directly.
    I think youre getting the idea wrong. The pressurised water at 9 bar is not supposed to compress the puck further. The only thing that should be compressing the puck is the tamper. The whole point of pressurising the brew water is to force it through the little voids between the coffee grounds so that the water comes into contact with every single coffee particle in the puck, and diffuse into the pores on the coffee particles to dissolve the solubles and then flow through the pathways in the voids until it reaches the bottom of the filter basket, through the basket holes and into the cup. So in fact, the 9 bar of water EXPANDS the puck, not COMPRESSING it.

    Anyway, my opinion is that tamping pressure does affect the extraction to a certain extent, but it is dependent on your dose, distribution and grind size. Its related to the maximum packing density of any packed bed in relation to particle sizes (and of course shapes, but every coffee ground particle will be of slightly different shapes so lets not go there :P) and the extent of the bed expansion during extraction.

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    sorry to bring up an old topic, but this is very interesting.

    the general guideline for extracting espresso is 15kg of tamping force, 9 bar pressure, 30 second pours resulting in 30/60ml of espresso. the conventional wisdom is that all of those elements need to be present in order to extract good espresso, so it would be logical to deduce that each of those elements play a part.

    there appears to be some conjecture about the purpose of the tamp. some say it is to compact the grind and to eliminate the tiny air pockets in the puck. while others say it affects the rate of the pour and therefore affects the volume/time equation. both of these are subject to debate, given the puck will then be put through 9 bar of pressure by the machine, and therefore the puck will be compressed even further by the 9 bar of pressure, or that the tamp plays an insignificant role in determining the rate of pour (again, due to the 9 bar of pressure being so much more than the 15kg tamp).

    if the oble89 is correct, that the pressure in the pf is actually for the purposes of expanding the puck and consequently ensuring even water penetration, then it seems to me that this process actually counteracts the tamping pressure. in other words, tamping compresses the puck, and the pressure decompresses it. this appears to be consistent with the phenomenon that pucks expand to reach the showerhead during extraction, especially for fresh beans.

    all this begs the question - why compress the puck by tamping and then have it expand again under pressure? in my mind, it appears that the purpose of the tamp is to simply evenly distribute the grind, get rid of any clumps, and to make sure the grinds are level. one can therefore deduce that tamping to a specific weight does not affect the end result, as long as it distributions and de-clumps as intended.

    consequently, the weight of the tamp plays no part in the pour rate. the way that tamping affects pour rate is by eliminating channelling, by way of distributing, leveling and de-clumping.

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    I think you are getting closer John Smith, but perhaps not quite there. It isn't that the pressure expands the puck, it's the water absorbing into the pores within the coffee (I'm not talking about the void space between the grinds here, but actual pores in the coffee).

    Grind size will affect the rate at which this occurs, as a finer grind = greater surface area = faster absorption. I wouldn't speculate as to whether this specifically is an issue for quality or not.

    Considering the factors of dose, grind, and tamp together, something has just dawned on me. Perhaps the interrelation between the three factors is more important than any of them in isolation . Thinking out loud:

    There seem to be "rules of thumb" for puck compression (relative to the top of the basket), tamp pressure, and dose. Ignoring the dogma, we can probably arrive at those same requirements working backwards.

    - To get an even extraction (or best attempt at one), we probably want an essentially fixed bed (i.e. minimal movement of coffee).

    - To achieve a fixed bed the expanded puck should contact the shower screen with enough force that the grounds don't move when the water passes through them.

    - Tamping allows "overfilling" of the basket, so that there is enough coffee in it to fill the whole volume once wet and expanded. If the same amount of wetted coffee would normally take up more volume than is available under the shower screen, then the puck will compress against it.

    - An additional factor is that to achieve a good extraction (i.e. all the stuff you want, but little of the stuff you dont), you need a slow enough flow to allow extraction of the coffee oils, but not so slow that the tannins have time to extract.

    - Working to a constant tamped depth effectively fixes one of the variables (pre-expanded volume), which aids consistency. Since the volume is fixed, there is a narrow range of grind size, dose and tamp combinations which will give result in the having the right mass in the basket to give a fixed bed post expansion.

    So perhaps the purpose of the tamp is simply to fit sufficient mass of coffee into the basket to allow a fixed bed "post expansion".
    - Grind too coarse, under-dose and undertamp, and for the same post-tamp puck there won't be enough coffee to create a fixed bed.
    - Grind too fine, or overdose and overtamp and for the same post-tamp puck height, there is too much coffee in the basket and the flow will be too slow.

    This suggests to me that overtamping and undertamping are problematic only because if you are working to a fixed tamp depth, they mask the real problem (under/over dosing and/or grinds being too big/small). It also suggests that undertamping is more problematic because it will not result in a packed bed post extration, wheras overtamping is less of a problem provided you don't overdose (as the result will just be a reduced tamped volume).

    Thus the relationship between grind size, tamp pressure and puck height (with a few simplifing assumptions, ignoring a couple of factors ).


    Of course, this is just a thought experiment, and I am certainly not an expert.
    Last edited by MrJack; 7th August 2012 at 11:59 PM.

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    I don't know the mathematics behind it but I find that tamping pressure does affect the taste of my coffee. I tend to get thin underextracted gushers whenever I try to reduce the tamp pressure (under 15kg pressure) even though the coffee in the portafilter seem to be compacted with even distribution.

  49. #49
    enjoy black coffee JamesM's Avatar
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    dunno about tamping pressure, but polishing, and precision fit tampers, are BS.

  50. #50
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    Behmor Brazen - $249 - Free Freight
    Quote Originally Posted by JamesM View Post
    dunno about tamping pressure, but polishing, and precision fit tampers, are BS.
    But you keep your Reg Barber

    To me I agree to some extent but the function of the tamper nowadays for me is to indicate correct dose level as well as reduce the mess I make in the tamping process. I know a correct dose by the tamp level as well as the pressure on the tamp. I grind so that when I press down on the tamper there is certain feel on the tamp because you can underdose and lightly tamp to get to a certain level and overdose and gorrilla tamp and still get to the same level...it's consistancy so grind and tamp to a pressure to know what's in your basket. I do weigh the beans on a scale but the scale is to the nearest gm so that could be up to 4 extra beans in the grinder. doesn't sound like much but it could mean an underdose or an overdose. I compensate by (don't do this at home ) 3/4 locking if overdose or full lock to max if underdosed. The reason for the locking position is again to allow for correct expansion of the puck. It's dangerous to partially lock your pf to compensate for an overdose as you may risk a rocketing pf into your beautiful cup. Do so at your own risk. Or better yet, don't do it, and instead redose correctly.

    Now regarding a precise fit or not, again to me it's about the level of the tamp to indicate correct dose...if I have a stack of untamped ground all around the basket, I've not really tamped to tell me that I've got the right amount of grind in the basket.
    HOWEVER, if you use other indicators to get the right dose other than the tamper then there is no argument, just use the plastic tamper on your commercial grinder or even use the plastic tamper that came with the machine you bought.

    I like to polish to get rid of that annoying static ground that might stick to the bottom of my tamper. It does nothing and yes it might aggitate the puck if you're rough...but meh...as everybody against fussy tamping says, the swell of the puck and pressure will sort that out anyway.



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