What is tamping espresso, why is it important and what is the right method?
Tamping compresses the fluffy dose of coffee grounds into an evenly dense coffee bed, so when high pressure water is forced through, it has to do the work of absorbing all those flavors before going into your cup as espresso.
If there’s air between the coffee grounds, the water will find it (water takes the path of least resistance) and zip through those less dense areas more quickly. This is dreaded channeling, which produces over extracted espresso, under extracted espresso, and a disappointing morning, all at the same time.
I decided to run a small and pretty entertaining experiment for my own education, and made a few shots of espresso without tamping, just to see what would happen. Brewing the shot was pretty ugly:
The first image is at 3 seconds, espresso extracting in a "donut" on the edge of the basket. The next image (7 seconds) reveals heavy channeling, with espresso leaving in multiple streams while other areas aren't being extracted at all. The third image is at 18 seconds, near the end of the extraction time, and there are still 3 streams of espresso. The espresso only collects into one stream at the very end of extraction, at 27 seconds.
The puck is cracked all around the edge, and there is a huge crater in the side of the puck. The shot tasted thin, bitter, and sour all at the same time.
I made another few shots with an uneven tamp and it came out, well, unevenly. The espresso clearly favored one side of the basket and the drink was not *as* bad as the completely un-tamped version- but it still tasted pretty bad. The shot had a better texture than the previous one, but was still pretty sour and bitter.
So my evenly tamped shot, while not perfect, tasted great. In the first image, the espresso is beginning extraction evenly across the surface of the filter basket. At 3 seconds, there are three streams, and at 5 seconds, they collect into one stream of espresso. The last shot is at 26 seconds, and shows the striping of dark and light brown that indicates good extraction.
It wasn't exactly in the center, but it came out balanced, with just a little bit of sweetness rather than bitterness, and a smooth texture to the shot. So in case you needed visual confirmation: tamping makes better espresso.
First, make sure you have the right tamper- one that fits well in your hand and in your portafilter, one you enjoy using. Using one that doesn’t fit you can be uncomfortable and potentially bad for your wrist, and using one that’s too small for your portafilter can lead to channeling around the edges.
The way you stand and hold your body is important too, as you want to keep everything aligned in such a way that you aren’t straining yourself. Turn your body to the side, so you come towards the counter hip first, which allows you to press on the coffee bed using the strength in your shoulder instead of just your elbow and wrist.
Most coffee blogs recommend 30 pounds of pressure, which sounds great, but maybe isn't the most intuitive of measurements. You can take a bathroom scale and push down to get the "feeling" of that amount of force- I found I was pushing with about 35 lbs. of pressure, which was more than I needed, so I backed off a bit.
If you don't want to put your bathroom scale on the counter, another good way to practice is to press down on your tamping mat until you feel the counter “push up” against you- that’s the feeling you should get from the coffee as you tamp it down. Once you get to that point, you aren't going to compress the puck any more, so just stop there.
- Hold the tamper handle as though you were holding a doorknob, and keep your wrist straight as you tamp.
- Place the portafilter edge flat against your tamping mat or stand, if it's bottomless. If it's double spouted, rest the spouts and handle on the bench. I find it’s easier for me to stay level if the basket is flat to begin with.
- Turn your body so you are standing with your hip to the counter, or angled towards the counter (not straight ahead).
- Get your elbow up so you’re coming straight down on the coffee bed.
- Press against the grounds and maintain a steady pressure, until the tamper stops moving. If you can’t go any further, you’re done.
- You can spin the tamper, which baristas call “polishing,” but it doesn’t do anything- though it does look cool.
- I check the tamper handle to see if it’s slightly askew, which lets me know if I was coming in at an angle of any kind. You can also use your fingers to feel how level the tamper is in relation to the portafilter edge.
- Don’t try to adjust from here- if you’re a bit off kilter, just keep that in mind for the next shot you make. If you’re REALLY off… well, make the shot and see what it tastes like. It’s always good to know what you’re trying to avoid.
- Don’t jostle or bump the portafilter on the way to the group head, as it might loosen the puck or crack it.
- Pull your shot and enjoy!
Nailing down the proper technique requires a little practice- just remember that even, consistent pressure is more important than lots of force. The end result is delicious coffee- so it's definitely worth the effort!