Tamping pressure and effect

[pie_in_ear]

There has been a lot of discussion about correct tamp pressure on the forums lately and I wanted to start a new topic to discuss it.

First off. Within reason I think that tamp pressure has very little effect on the pour. Effectively, the tamp is only sealing the puck from the initial pre-infusion. Once the puck is saturated it expands and your tamp pressure is irrelevent.

This also brings dosing into the equation, as your dose increases your puck expansion decreases. I think people are way to obsessed with updosing. We have been playing with dosing (thanks to Scotts tools which enable us to measure our dose accurately) and are discovering some very interesting results with grind & dose relationships.

Here is what we are aiming for, a 25 sec, 2 x 25 ml pour, from our double deep baskets (18gm). Regular dose is around 18gm, up dose can be as much as 20gm, under dosed as little as 16gm. There are about 20 steps inbetween 20 and 16 gram doses. At each step we get the grind right, taste, evaluate, change tamp (8Kg, 13 Kg, 20 Kg), evaluate. We repeated this with 3 different coffees. There are some interesting results.

1) The tamp pressure has very little effect on the taste of the espresso. There is a minor difference in the intitial few drops of the heavy tamp, but hardly detectable.
2) The espresso of each step had a different flavour. The best dose depended on type of coffee and age of beans.
3) We found as the coffee aged the required dose to get a consistant espresso flavour was changing.
4) As the dose decreased, the tamp pressure had a larger effect, but still very minor compared to the effect of the dose.

Our conclusions were that dose and grind are by far the most important things to consider. Tamp pressure is somewhat irrelevent as we were able to repeat the results of our dose-grind relationship between 3 baristas, all with different tamps. We are even starting to look at how important distribution is, I have had a very presise distribution method for years, and I am starting to get great results without doing any distribution. I am even looking at getting some 16gm Baskets to play with dose Vs basket size.

It just gows to show that you learn things everyday and can always improve what you do. It has improved our espresso making process majorly in terms of consistency from shot to shot and barsita to barista.

Would love to hear others thoughts.

[nunu]

Re: Tamping pressure and effect

I always tamp very firmly (read stand on it). Ive found that dose is probably the most important factor from shot to shot, once grind is dialled in.

Im usually dosing around the 16g mark. If the coffee is "fluffier" its closer to 15g. I say around, because my scale only has a resolution of 1g.

On the grind front, Ive seen the grinder go nearly 6 "bumps" change in two weeks with the same coffee as it ages. Would also have some sort of impact on the shot methinks.

[Dimal]

Re: Tamping pressure and effect

Yep,

Agree with you wholeheartedly Jason. My experience has also led me to a position where Dosing is the supremo element of the process to get right on a consistent basis. Due to a couple of strokes, it is really difficult for me to apply a consistent tamping force which can vary from a low of about 7Kg to maybe 12-12.5Kg. None of this seems to make a lot of difference to the shot outcome but the method needs to be consistent and I can manage that ok.

By far the biggest influence on shot quality outcome for me has been consistency with dosing, as you described above and once I worked out how to do this everything else started to fall into place behind this. It also makes sense that as dose is reduced, a variable tamping force will have an increasingly marked affect on the outcome but for all the machines Ive had a go at using, I usually dose such that the puck finishes up about 6mm below the rim with maybe just a touch on the shower-screen.... not always though.

Its an interesting aspect of the espresso making process though. Greg Pullman completed some experiments last year to try and establish the physical processes involved when varying the tamping pressure, and the results pretty well parallel the outcome re quality of the brew that you have observed. Interesting stuff mate.... [smiley=thumbsup.gif]

Mal.

[askthecoffeeguy]

Re: Tamping pressure and effect

Too true but I reckon that many domestic machines, especially those with a small boiler capacity are much more sensitive to tamp and grind.

And even at my work when the weather plays havoc with my grind I sometimes find that a lighter tamp gets a much better extraction (if its cool) and a firmer one (when its warm which is not often in Melbourne its either cold or bloody hot!) produces the same result...

Pat