What difference in taste between grinding finer and tamping harder?

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StefanoB

#1: Post by StefanoB »

I have read the sticky over thread in this forum, what the "newbie" videos (all featuring very precious informations ! Thanks for that ! :D ), made some research, but there is something I have found but should be quite basic.

When the flow is a bit too fast (and you don't want to modify the dose), two choices are possible:
1) grinding just a notch finer ;
2) tamping harder (assuming you were tamping rather light to get this fast flow)

Will the two possible modifications above affect similarly the result in the cup? Let's say, in case we keep the ratio constant (so extraction time will increase).
Stefano

Jeff
Team HB

#2: Post by Jeff »

Within reason, tamping harder doesn't change extraction flow rate significantly.

Once you've tamped a uniform and level bed sufficiently to prevent major channeling, the extraction pressure will dominate. 8 bar is over 100 psi. Major "gorilla" tamp required to come even remotely close to that with around 4 sq.in. in a 58 mm basket.

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StefanoB (original poster)

#3: Post by StefanoB (original poster) »

Thank you jeff for your answer. However, this is not my experience with my machine, but it is a manuel lever machine, the Elektra Microcasa a Leva, with a particular pressure profile fixed by the spring. What I experience is that changing tamping pressure from 15lbs to 33lbs decrease the speed of the flow (thus changing the result in the cup), more or less similarly to what I obtain by grinding 1/2 click finer on my Commandante C40 (with Redclix). I am quite new with it, so I didn't do many tests with it yet to draw a rationale of what to expect in terms of taste modification with one or the other option. This is while I was asking.

Maybe I should have posted this question in the Lever forum?...
Stefano

Jeff
Team HB

#4: Post by Jeff »

What taste difference to expect between grinding finer and tamping harder, on a spring lever machine?

How the pressure is generated is immaterial. An old-school 30# tamp is around 8 psi, around 1/2 bar, more than an order of magnitude less than typical 6-8 bar extraction pressures.

First, I doubt your tamping at 7-15 bar as that is several hundred pounds of force, even with the slightly smaller area of your lever machine's basket.

If you're only tamping at 7-15 pounds of force, it is likely that your puck prep is poor enough that you're not getting uniform flow though the puck. That you have multiple threads around puck cracking and other extraction issues suggest to me that your basic technique can still stand improvement.

ojt

#5: Post by ojt »

IMHO you are much more likely to experience difference in brew temperature which then influences the pucks resistance and ultimately the taste.

Case in point: I still to date only have the default Pavoni plastic tamper, which I sanded down to fit the baskets perfectly (the butt end was larger than the basket diameter). I brew quite consistently and good brews. I don't feel a big difference in pressure shot to shot, nor perceive taste differences unless I intentionally change other parameters. Also, I have a grouphead thermometer and know quite well which temperature to pull my shots at.
Osku

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StefanoB (original poster)

#6: Post by StefanoB (original poster) »

Jeff wrote: First, I doubt your tamping at 7-15 bar as that is several hundred pounds of force, even with the slightly smaller area of your lever machine's basket.
I am very sorry, it was a mistake in my OP I have now corrected, it was supposed to be not bar but kgs... I am varying tamping force between 15lbs and 33lbs actually.

With the MCAL I see a significant difference in flow speed when varying the tamping pressure between these two applied force. I can precisely control that from the brand new Eazytamp 5 star pro calibrated tamper I am using, because you can chance the spring, and I have 15lbs, 22lbs and 33lbs springs.

Jeff wrote: If you're only tamping at 7-15 pounds of force, it is likely that your puck prep is poor enough that you're not getting uniform flow though the puck. That you have multiple threads around puck cracking and other extraction issues suggest to me that your basic technique can still stand improvement.
I have read on some thread related to MCAL and La Pavoni that some seasoned users of these lever machines advocate a very light tamp, so initially I was barely tamping (just finger tamp on the extremity). This was one of the reasons of the uneven extraction I was having (other reasons was over- and then underfilling the baskets, and also changing the shower screen to a IMS precision improved things).

Now it is solved, I have very nice extractions (super good) and nice pucks, just a persistent donut issue at preinfusion but which does not affect the taste of the coffee.
Stefano

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StefanoB (original poster)

#7: Post by StefanoB (original poster) »

ojt wrote:IMHO you are much more likely to experience difference in brew temperature which then influences the pucks resistance and ultimately the taste.
Good point! My extraction temperature do vary a bit from shot to shot indeed, because with this machine it is difficult to precisely control the temperature. Even when, for good monitoring, I have attached a digital thermometer to the groudhead, from shot to shot I can extract with 1-2°C of difference. Also, I have been playing with switching off the boiler in order to extract at 0.8 Bar (instead of standard 1.1±0.1 bar), to have a less aggressive water flow, but this of course affect also the water temperature in the puck during extraction...

How would you rationalise the influence of temperature on pucks resistance: higher temp. leads to faster flow or the opposite?

ojt wrote:Case in point: I still to date only have the default Pavoni plastic tamper, which I sanded down to fit the baskets perfectly (the butt end was larger than the basket diameter). I brew quite consistently and good brews. I don't feel a big difference in pressure shot to shot, nor perceive taste differences unless I intentionally change other parameters. Also, I have a grouphead thermometer and know quite well which temperature to pull my shots at.
Ok...
Stefano

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#8: Post by DamianWarS »

StefanoB wrote:I have read the sticky over thread in this forum, what the "newbie" videos (all featuring very precious informations ! Thanks for that ! :D ), made some research, but there is something I have found but should be quite basic.

When the flow is a bit too fast (and you don't want to modify the dose), two choices are possible:
1) grinding just a notch finer ;
2) tamping harder (assuming you were tamping rather light to get this fast flow)

Will the two possible modifications above affect similarly the result in the cup? Let's say, in case we keep the ratio constant (so extraction time will increase).
a hard tamp has little impact (no pun intended) on the speed of the shot with the exception of a nutating tamp which is completely different. the pressure of the machine itself pushes on the coffee bed and can have a tamping effect so even if you tamp lightly there are still pressures pushing down on the coffee bed greater than you can "hard" tamp and there is a point where you can't be more effective at this, that point is not that hard, I think 5kg of force is sufficient to reach this point.

However, let's assume your tamp pressure does make a difference that slows down a shot comparable to grinding a step finer. Let's call shot A the finer grind and shot B the hard tamp. Shot A has more coffee surface area from griding finer and will extract higher. So the fine grind not only slows the shot (which increases the extraction) but it also increases the surface area (which increases the extract). Effectively you've made one change that has impacted 2 factors. This is why often grinding finer and dosing down are done together.

Whereas with Shot B by tamping harder to slow the shot, even let's say a perfectly executed nutating tamp, only slows the shot but it doesn't impact the surface area of the coffee so the only increase of extraction would be from an increase of shot time not surface area so the impact is only 1 factor.

Shot A should extract higher and end up with a greater TDS in the cup where Shot B would maybe extract higher than the control because it has longer contact time but it would probably be lower extraction to Shot A and have a lower TDS in the cup (assuming the shot time and yield are exactly the same). In reality, the hard tamp probably would do nothing, not even change the shot time.

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StefanoB (original poster)

#9: Post by StefanoB (original poster) »

Thank you very much! I like this reasoning! 8)

What I would like to rationalize, is the effect on taste. If I try to slow down the shot, is to extract more nice flavors, and at the same time try no to extract the unpleasant flavors such as bitterness.

I guess by grinding finer I risk extracting bitterness, while playing with tamp pressure only probably is safer to avoid that? Would you agree?...

Another question: I have tried nutation without seeing obvious differences than with direct tamp, but my nutation technique is probably poor. With a good nutation tamp which changes would you expect to see in the cup?
Stefano

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StefanoB (original poster)

#10: Post by StefanoB (original poster) »

I have found this video:

http://www.youtube.com/watch?v=9l0dnXHM1cU

At 2:00 and onward we can see shots run in parallel, where only the tamping force (from 5 lbs to 40 lbs) varied.

On the contrary to what it is said in the video, we can see as a result that, for the same shot time, the weight in the cup vary markedly (from 35.8g with a 5lbs tamp to 26.4lbs with a 40lbs tamp), and thus so does the flow, lighter tamp leading to faster flow.

However, it is non-linear: the weight at 23lbs tamp is very close to the weight obtained with 40lbs tamp.

Therefore, it seems that the tamping pressure does not significantly affect the flow, but provided the tamping pressure (at least in this experience) is at least 20+ lbs.

This is why I see a difference between my "light finger tamp" (5-10lbs?), calibrated 15lbs and calibrated 33lbs tamps...
Stefano