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January 30, 2017 /
How Hard Should You Tamp?

Tamping for espresso is riddled with an incredible amount of folk-knowledge. When I was taught espresso in 2008, I was told to practice tamping on bathroom scales (I admit I don’t remember what the prescribed weight was). Today I’d like to shed some light on tamping pressure and how easy it is to get it right.

tl:dr – Tamping pressure matters. If you press until the tamper stops moving down, and keep it level, you’re golden

Tamping is pretty simple. You’re compressing the coffee grinds to promote even extraction in an ergonomic and consistent way.

Let’s break that down a little further:

Compressing the Grinds

If there’s air between the grinds, water will treat it as a shortcut and speed through. If there’s no (or minimal) air, the grinds will slow the water down.

Unfortunately, coffee grinds aren’t always uniformly dense, and ‘somewhere between fluffy and compact’ isn’t very precise. So we need to compress them together, eliminating that void space. This way, the grind size is the deciding factor for flow rate; not the amount of air between the grinds.

Promote an Even Extraction

Tamping should create a bed of coffee with even density. Even density means there’s no shortcuts or ‘easy ways through’ for the water.

You really want the water to flow through the entire mass of grinds as evenly as possible. Water is dumb, it takes the easy route. If there’s an area of lower density, the water will travel through it more quickly. The grinds in that area will be over extracted and the rest will be under extracted.

To achieve even density we need a perfectly flat, horizontal bed of coffee. Flat tampers are crucial here. If you have a curved tamper, throw it out and buy a flat one. And of course your tamping technique should always be perfectly horizontal.

Ergonomic

The amount of pressure applied should be as small as possible, without sacrificing any of the above. Repetitive strain injuries are too common amongst Baristas, so aiming for the lightest pressure that works is key.

Consistent

You want to control the flow rate of your espresso by adjusting grind size, not tamping pressure. If tamping pressure is a variable then you need to do it the same every single time. This is, frankly, a ridiculous ask for a human and should be entirely avoided. Luckily, there’s an easy way to almost eliminate tamping pressure as a variable.

Maximum Density

Tamping squeezes the air from between the grinds. There’s only so much air in there, and eventually the grinds can’t compress any further. At a certain tamping pressure, you’ll hit ‘maximum density’. At this point, the grinds are fully compressed (on the vertical axis). No matter how hard you try, they won’t move any further. Coffee beans are super tough. You can’t crush or damage them with a tamper because the load is distributed across millions of particles.

This is great news for consistency and ergonomics, because:
1) There’s no maximum tamping pressure. You can’t overdo it. Hercules can’t overdo it. The only thing you can do is approach maximum density. Once you’re there, the job is done.

2) Maximum density doesn’t require much pressure.

To find out how little pressure is required try slowly increasing the pressure you apply with the tamper. At maximum density, the tamper will stop moving. If you keep applying pressure, it won’t move any further.

When the tamper stops moving, that’s when you stop pressing.

Why You Shouldn’t Tamp Any Lighter

As I mentioned earlier, you don’t want to rely on tamping pressure as a variable because humans aren’t consistent.

If you tamp lighter, it’s almost impossible to do so consistently. Slight changes in pressure will result in drastic changes to density (and hence, flow rate). The only way you can wipe out this human error is by achieving maximum density. Here’s a little graph to explain:


If it’s lighter than you’re used to, great! Enjoy a healthier barista life.

If it’s a bit harder than you’re used to, great! Enjoy the tasty benefits of consistent density.

 

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Glenn Adams
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Glenn Adams

My question is wouldn’t tamp pressure be more important when using a unpressurized porta filter vs a pressurized one?

Tampers (again) – It All Started Here
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Tampers (again) – It All Started Here

[…] Pete from Clockwork gave his thoughts on the Barista Hustle Facebook group, making reference to to Matt Perger’s article on maximum density: […]

Duncan
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Duncan

I’ve also found that, although tamping pressure doesn’t necessarily affect the coffee, tamping again and again and again can have an affect on the extraction of the coffee. I have only been a barista for a few months but early on an old timer told me to tamp leaning north, south, east and west and nothing came out as it affected the grind. This has stayed with me and have been acutely aware that the coffee knows what it is doing and, like the water, moves where it needs to when given freedom. Being new to the game and in… Read more »

Duncan
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Duncan

I find that the tamper needs a little bit of freedom during the tamp to find areas of the grind scape, in the porta-filter, that aren’t as consistent. Regardless off what you do to even the coffee in the porta-filter before hand, horizontally and vertically. The humidity in my area varies a lot and the coffee reacts differently day to day and the coffee tends to clump if and when it is fiddled with too much which makes this method of tamp more important.

Martin Luff
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Martin Luff

Great work with the Hustle Matt. Finally, a place to find actual, validated info from a pro. A much needed and generous idea to share your extensive knowledge – keep up the good work. A question on tamping pressure, like many I’ve had it drilled in to me for years about using a specific tamp pressure, and now you’ve thrown that all out of the window. Can it really be true that there is no such thing as ‘too much’ tamping pressure? So as long as the pre-tamp distribution is thorough and the pressure is even / square, then it’s… Read more »

John Cain
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John Cain

Great blog – thanks Matt. As I read this, I recalled a passage from Scott Rao’s “Espresso Extraction” – “Tamping pressure influences head space above grounds and preinfusion time. increased tamping pressure has little effect on flow rate once full pressure is reached but delays the onset of full pressure, wreaking havoc on the machine’s intended pressure curve”.

Is it correct to assume that once maximum density has been reached, increased tamping pressure wouldn’t have any impact on the preinfusion time?

Thanks!
John

Alex
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Alex

What is nutating?

alexevansohio
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alexevansohio

I’ve never seen anyone choke a machine that was otherwise pulling shots within range simply by tamping harder. There’s always another factor at play — an increased dose, a finer grind, etc. The only possible exception I could see would be nutating, but folks shouldn’t be doing that anyway, and it’s not really “tamping” in the traditional sense.

Alex
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Alex

If you can’t overdo it how come it’s sometimes possible to nearly choke the machine? Are you saying the grind is off and needs to be adjusted to be coarser?

Love coffee? Encourage baristas to love and take care of their bodies. – Movementary Micky
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Love coffee? Encourage baristas to love and take care of their bodies. – Movementary Micky

[…] the most? I will have to get to that some other time!) As explained in more detail on the blog of Barista Hustle, the goal with tamping is gently squeezing out the air pockets between the coffee grinds and to […]

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