You know your tamp is correct if the espresso puck is level and smooth, comes out in one piece, and leads to a balanced extraction (not too bitter/sour) with a steady flow rate (around 25-30 seconds for a standard shot). Key signs of a good tamp are a flat puck, no grounds stuck to the basket sides, even flow during brewing, and a balanced taste in the cup, while channeling or spurting indicates an uneven tamp.
Signs of Under or Over-Tamping: Under-tamping leads to fast water flow and weak espresso, while over-tamping slows water flow and creates bitter flavors.
At a certain point (usually around 30 pounds of force), you have filled in all the air pockets in your untamped bed with ground coffee. After this point, it is impossible to tamp further. There is physically no where else you can make the coffee go with human force. So, always tamp with as much force as you can.
In simple terms, a 2:1 ratio means you're extracting twice as much liquid espresso as the weight of the coffee grounds you use. For example: 18 grams of ground coffee in = 36 grams of espresso out.
The hardest thing for a barista to make is a Ristretto. This coffee extraction is known for its precise balance, being the first part of an espresso shot that's smoother and sweeter.
The 25 to 30 Second Extraction Rule
For a double shot, aim for 25 to 30 seconds of extraction to yield 35 to 40 grams of espresso, about 2 ounces. How to adjust: Grind size has the biggest impact: finer slows extraction, coarser speeds it up. Dose matters too: more coffee slows extraction.
The 80/20 rule for coffee states that 20% of the brewing variables contribute to 80% of the final flavour quality. Focus on water temperature and grind size because these primary factors dictate the success of your extraction process.
More and more baristas are finding that tamping pressure is overrated—hard on the wrist and cause an over-extracted, bitter brew. Use a twisting motion as you pull up to “polish” the puck. Just be sure not to twist as you push down, which will disturb the packed coffee.
Tamp twice. For the first tamp, apply a light amount of pressure to form a puck shape and for the second use give it a bit more force and press heavily down to remove any obvious spaces between the grinds.
Hold your portafilter firm and level on the tamp mat or stand (it's important that the portafilter basket is flat, and that you are not tamping at an angle). Grasp your tamper as if you are shaking hands with a doorknob, and apply light, even, and equal force to the coffee bed.
Espresso is defined at around 9 bars of pressure. Some machines advertise 15–20 bar pumps, but that figure refers to maximum pump output, not the pressure used for brewing. The best espresso comes from a stable 9 bar; anything higher doesn't improve flavour.
A very common issue for the Barista Express is where the water won't come through the group head (the bit that you connect the porta filter to) when making coffee. Usually the steam-wand and hot water outlet are still working (sometimes they are not working either).
And below we have the top ten mistakes home baristas can make:
Four minutes or less. That is how long the Starbucks chief executive officer would like for it to take from order to drink in hand. The new operating model is called "Green Apron Service," according to WGN.
From holding up the queue to making unreasonable demands, these 10 habits will annoy your barista.
3. Thin flavor. The under-extracted espresso doesn't have the full range of flavors extracted from the ground coffee. Compared with a well extracted espresso, which is more full bodied and syrupy, an under-extracted espresso will not only deliver an unpleasant sourness, but it will also taste watery and thin.
A sturdy measuring cup could become a makeshift tamper. A thumb: once you do not have any tool to tamp, use your thumb. Move your thumb in a circular motion. Then, you move from a section to the next one with slight pressure.
Let's say you are brewing a double shot espresso (1:2 ratio); you should expect the total ground coffee to equal 18 – 20 grams. Dosing your coffee also refers to correctly choosing your grind size, as your grind size will significantly impact your extraction yield and shot time.
The Espresso Golden Ratio
The golden ratio for espresso brewing is typically a 1:2 to 1:2.5 coffee-to-water ratio – that's one part coffee to two to two and a half parts water.
Serving Size. Most standard espresso cups are designed so that they can serve a single shot of espresso with an average serving size of 30ml, and double shot of espresso, with an average serving size of 60ml.