Tamping is the act of compressing ground coffee in an espresso filter with a compressor before brewing to ensure a uniform espresso extraction because the water from the Espresso machine has tremendous pressure. If the coffee layer inside the filter funnel is unevenly distributed and tight, the water will only go through the core between the delicate coffee areas – low pressure, leaving behind “dry” areas and creating an uneven extraction.
Therefore, the purpose of Tamping is to remove “paths” (also called drainage channels) of low resistance in the coffee powder and force the water to permeate evenly for a uniform extraction.
Purpose and tools of Tamping?
The main task of the compression operation is to remove excess space and make the coffee powder in the basket tighter, creating a uniform resistance on the surface of the coffee layer, so under tremendous pressure from the machine. When brewing Espresso, the extraction will be more even, limiting the condition of Channelling (The phenomenon of hot water creeping through the slits, the places where the coffee is unevenly distributed in the brewing hand – making the extraction taste less – Under Extracted).
Tamping is a balancing act between three variables. You have to practice some exercises to get the hang of it, but it’s pretty easy to become consistent once you get it.
- Coffee Layer Distribution – Before getting your Tamper, you need to ensure that the coffee has been distributed relatively evenly in the portafilter. Tamping on an unbalanced coffee surface will not make sense.
- Tamping Angle – Make sure you press the tamper perpendicular to the coffee layer. Otherwise, water will flow down the angle of the filter, creating a drain channel and resulting in an unbalanced shot.
- Tamping Pressure – Most official guidelines recommend 30 pounds (about 13kg), but as long as you’re using 5kg+, it’s okay. The most important part is not the exact amount of pressure but the consistency with achieving that pressure every time – see more below.
Note about compression when tamping!
First of all, it is essential to know that the force of Tamping when Tamping depends on many different factors, including the pressure generated by the Espresso machine, the quality of the beans, the fineness of the ground coffee and the freshness of the coffee used…
However, the issue of compression when Tamping still receives a lot of debate, between should squeeze be tight or just moderate compression? As an explanation for this, according to Scott Rao, the most muscular contraction produced by the barista in the range of 22.5kg (50 lb) is practically no help to the more than 225kg (approximately 500 lb) force generated by the machine. Espresso under 9 bar pressure. So performing a standard compression of 9-13kg (20-30lb) will save more effort and evenly distribute the coffee layer in the basket.