Tamping is a fundamental skill and technique required when preparing espresso coffee. This is a how to guide which looks into the processes and reasons why tamping is necessary in the preparation of espresso.
There are a few key steps to ensure an accurate well executed tamp, this together with the correct ergonomic techniques will ensure that not only does your coffee taste good but you avoid any long term issues with repetitive stress injury - especially if you use an espresso machine for a living. The method that I will outline here applies to hand held tamps as these are by far the most widely used.
This process will be based on the fact that you have already dosed the correct amount of ground coffee into the filter basket, if you would like to find out some more please visit my post on dosing.
Start tamping by lightly sitting your tamp in the filter basket, ensure that both the tamp is sitting level in the basket and that the group handle is being held level and sitting on a bench top. Then remove the tamp - this will work by gently leveling the coffee in the basket.
The tamp should be held in a similar manner to how you would hold onto a bicycle handle, the handle of the tamp sitting in the palm of your hand with thumb resting on the base of the tamp. Using this grip place the tamp back into the filter basket, at this stage your forearm should be positioned vertically above the tamp to minimise muscle strain using the strength in your arm push directly down using firm pressure. This action will compress the grounds, if you have dialled in your grind using more pressure here will slow down the pour, less pressure will speed up the pour.
After applying the downward pressure, release the tamp - without lifting it out of the basket. Simply use your fingertips to gently twist the tamp. This is the process is referred to as polishing, it helps to smooth out surface of the puck and also release the tamp. If you simply lift the tamp off the basket before polishing you run the risk of the grinds sticking to the base of the tamp.
Some schools of though suggest tapping the group handle to release any coffee grounds, however I would not recommend doing this as you run the risk of creating cracks or channels in the coffee puck. So there you have it, the process of tamping. For those visual learners out there I have embedded a YouTube video from the crew at Seattle Coffee Gear which runs through the process for a visual demonstration of the whole process. Enjoy!