How to Tamp Espresso Coffee Puck? How Much Pressure Should You Apply When Tamping?

The Art of Tamping: A De-stressing Observation

Sometimes, observing a barista's tamping technique can be a de-stressing experience! This is because every barista has a different understanding of tamping, resulting in unique tamping movements.

The Consensus and Divergence in Tamping

There's general agreement that tamping the coffee grounds evenly is essential. Uneven tamping with one side higher than the other will cause channeling, leading to uneven extraction. However, where baristas differ is in their understanding of how much pressure should be applied to properly compact the coffee grounds.

Two Different Schools of Tamping

Baristas who believe that simply creating a level and compact coffee puck is sufficient typically apply gentle rotation of the tamper with slight pressure during tamping. Their entire movement flows like water—graceful and elegant. They believe that regardless of how much force is applied, the density of the coffee puck becomes insignificant when faced with the high-pressure extraction of an espresso machine!

In contrast, if you encounter a barista who believes in using maximum force to thoroughly compact the coffee puck, you might witness all their strength channeled into their tamping arm! Using what appears to be enough force to lift themselves, they tamp as if declaring that either the table or the coffee grounds must be level! They believe that the force used to tamp the puck can effectively control flow rate—greater force leads to more even extraction.

The Tamping Experiment

So, how much pressure should we actually apply when tamping a coffee puck?

FrontStreet Coffee will conduct experiments using both fine and coarse grind settings, creating two groups of tests with different tamping pressures for each group. Let's see whether controlling tamping pressure is truly necessary! The experiment will use a Galileo Q18 grinder, with a 20g dose and a target extraction weight of 40ml. The fine grind setting is 1.5, while the coarse grind setting is 2.5. We'll evaluate whether tamping pressure affects extraction by measuring extraction time!

(The left image shows coffee grounds ground at setting 1.5, while the right image shows grounds at setting 2.5)

Fine Grind Tamping Comparison

Using 20g of coffee ground at setting 1.5, after distribution, we applied different levels of pressure: 1.5kg (normal) force and maximum force.

(The electronic scale's maximum capacity is 3kg, so we borrowed our neighbor's body weight scale. The maximum force tamping measured approximately 9kg.)

The 20g puck tamped with 1.5kg force required 30 seconds to extract 40ml of liquid, while the puck tamped with maximum force required 33 seconds. To prevent variations in the coffee grounds, we repeated the extraction and the time remained 33 seconds. This shows that for finely ground coffee, changes in tamping pressure do affect extraction.

Coarse Grind Tamping Comparison

Similarly, after distribution, we applied different levels of pressure—1.5kg and maximum force—to tamp the coarse ground coffee puck. The results were surprisingly consistent, with both requiring 20 seconds to extract 40ml of liquid (shorter time due to the coarser grind).

Experimental Conclusion

From the above experiments, we can see that differences in coffee ground density lead to varying force requirements to achieve optimal puck compaction. What does this mean? For instance, our fine grind experiment produced different results due to varying tamping pressures because the coffee particles were smaller. Compacting them to a dense state requires greater force! The 1.5kg tamping pressure was clearly insufficient—it needed more force to achieve maximum compaction.

If we slightly increased the force to 2kg, the extraction time matched that of the maximum-force tamped puck, because at this point, both pucks had reached the same level of compaction, naturally requiring the same extraction time! The coarse grind experiment demonstrates this point well—because there are larger gaps between coffee particles in the puck, 1.5kg pressure was sufficient to achieve optimal compaction. Therefore, even if you use maximum force to tamp the puck, the extraction results will be nearly identical to those achieved with 1.5kg pressure.

Therefore, we can appropriately adjust the tamping force needed for different grind sizes—the finer the grind, the slightly more force can be applied~

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