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The most important article about Tamping you'll ever read

Tamping is one of the crucial steps to espresso preparation. Many baristas have been taught to tamp evenly with 30 pounds of pressure and to ensure tamping levelness. Today there are also different tampers from flat bases to concave to ribbed surfaces and even different base sizes. This week we set out to test two different aspects of tamping; the levelness of a tamp, the tamper's base size and their effects on the resulting espresso.
Tamping is one of the crucial steps to espresso preparation. Many baristas have been taught to tamp evenly with 30 pounds of pressure and to ensure tamping levelness. Today there are also different tampers from flat bases to concave to ribbed surfaces and even different base sizes. This week we set out to test two different aspects of tamping; the levelness of a tamp, the tamper's base size and their effects on the resulting espresso.

If you are unfamiliar with the workings of expresso extraction percentages and the use of the coffee refractometer, you can always read our previous article over here : https://compoundcoffee.com/experiments/9_King-of-Distribution-Techniques to get a quick overview and understanding of espresso extraction percentages.

Now let's dive straight into the experiment!

Disclaimer : We are by no means statistical / math / science experts. This is just a simple experiment carried out to give us an idea of the performance of each method only. People are more than welcome to give their feedback on how we can improve and carry out a more academically approved experiment / report.

Coffee 

Ethiopia, Sidamo Guji
Process : Sundried Naturals
Variety: Ethiopian Heirloom
Roast Age: 8 days from roast date 
Agtron : 70 (Whole Bean), 90(Ground)

Equipment

Grinder : Nuova Simonelli Mythos One Climapro Grinder
Distribution Technique : Stockfleth Method
Tamper : (Controlled Variable) / Initial Calibration with Stock La Marzocco 58mm tamper
Portafilter Basket : VST 20g
Espresso Machine : Slayer V3
Coffee Refractometer : VST Coffee III
Calibration : 20g Dose, 40g Yield, Shot : 14s Pre-infusion slow ramp to 3 bar, 13s 9 bar full pressure, Total brew time: 27s
                   Water temperature : 91.3°C. Final EY 17.75% (La Marzocco Stock Tamper).
Dose Tolerance : 20g ± 0.1g
Shot Tolerance : 40.0g ±  0.5g

Null Hypothesis 1:
A crooked tamp does not have any impact on the espresso extraction percentage.

Null Hypothesis 2:
A larger diameter tamper base does not have any impact on the espresso extraction percentage.

The tamper that we will be using for the control is the stock La Marzocco(LM) 58mm wide base Tamper:



To test the impact of tamping levelness on extraction percentage, we will be pulling shots as per normal with the stock LM Tamper and comparing it to shots pulled with the LM Tamper at an intentionally uneven angle. The uneven angle is meaured at a rough 5mm above the top of the portafilter on the left side of the portafilter like below:

Crooked Tamper

To test the impact of a larger tamper base diameter on extraction percentage, we will be pulling shots on two tampers, the Pergtamp and the Levy Tamp to compare to the control. Both tampers utilise a 58.5mm diameter base.


Levy Tamp:
handle+options.jpg (750×438)

Pergtamp:



Methodology:

(Steps)
1. Pull 15 espresso shots using the calibrated settings using the LM Tamper.
2. Pull 15 espresso shots using the calibrated settings using the LM Tamper at a crooked angle.
3. Pull 15 espresso shots using the calibrated settings using the Pergtamp.
4. Pull 15 espresso shots using the calibrated settings using the Levy Tamp.
5. Wait for espresso shots to cool to room temperature.
6. Measure Total Dissolved Solids (TDS%) and Extraction % for each sample.

Results:



LM Tamper (Control)LM Tamper (Crooked)PergtampLevy Tamp
YieldTDSExt %YieldTDSExt %YieldTDSExt %YieldTDSExt %
140.18.6517.9740.18.7718.2239.68.3917.2139.99.1118.83
240.28.8918.5240.08.2917.1839.69.3219.1240.38.9518.69
340.18.3117.2740.18.3617.3740.29.2219.239.98.8118.21
440.18.1716.9740.58.7218.339.79.2218.9739.89.1318.83
539.88.6017.7339.78.7317.9639.99.2819.1940.08.6918.01
639.58.5917.5839.98.3717.340.39.0818.9640.08.9418.53
739.98.4317.4339.98.3617.2840.39.2319.2740.58.7018.26
839.58.6117.6239.88.4717.4739.59.2618.9540.09.1118.88
940.38.1617.0439.58.7317.8740.29.1719.139.58.9118.24
1039.88.4317.3839.78.8518.240.48.8518.5340.29.0718.89
1139.88.5417.6140.18.6517.9740.29.2719.3140.09.0118.67
1239.78.8918.2940.08.5017.6240.09.5319.7540.19.3419.41
1339.68.9718.440.08.6918.2139.89.1918.9540.19.3319.39
1439.58.7717.9540.28.6217.9539.79.2318.9940.39.2519.31
1539.68.9818.4339.98.6917.9739.69.4919.4740.28.7718.27
Average Ext %17.75%17.79%18.998%18.69%
Range1.55%1.12%2.54%1.38%
Standard Deviation0.5000.3870.5660.446
Variance0.2310.1500.3200.199
P-Value10.7834945686.41263E-077.81852E-06


Conclusion:

For those who might be unfamiliar with statistics, you can read  the conclusion of our previous article to get a quick explanation on statistical significance here: https://compoundcoffee.com/experiments/9_King-of-Distribution-Techniques

Based on the data that we found, comparing the extraction percentages of the Crooked LM Tamper to the stock LM Tamper yielded a P-value of 0.78. This means that we are unable to reject the Null Hypothesis 1 as we do not have a significant result. An uneven tamp level does not have any significant impact on espresso extraction percentages. Although taste is subjective, we do want to state that when we tasted the espressos from both methods, there was noticably more notes of over-extraction, particularly bitterness and astringency, in the shot with the unevem tamp level. Therefore we will not be belittling the importance of a level tamp any time soon. We would suggest others to test and taste for themselves to draw their own conclusion as we can only present the numbers as objective data.

The second set of data from the tampers with the larger 58.5mm diameter base yielded a P-value of less than 0.01. That means that we can confidently reject the Null Hypothesis 2. A larger 58.5mm diameter tamper base does have a significant impact on espresso extraction %. Based on the results, we may also infer that a larger 58.5mm diameter tamper base is correlated with a higher extraction %.

Looking into the future, we will be comparing the Pergtamp to the Levy Tamp specifically to compare the differences between the two tampers to see if the levelness of the Levy Tamper has a significant improvement over the Pergtamp since both have the same base diameter.

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2 Comments

    • Avatar
      ANG PENG HWA
      Sep 4, 2016

      Hi. The use of "null hypothesis" to test is wrong. Instead, you should just use hypothesis.Also, if you have the results, there is no need to "infer". You just show.You only infer when the results are indirect.Minor details.But keep up the experimentations.Ang

    • Avatar
      Kenneth
      Jun 6, 2017

      Thanks Ang! I'll keep that in mind when writing the future experiments!

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