The Operating Pump Pressure Is Wrong If your operating pump pressure is set too low, your coffee will dispense too slowly—or sometimes it won't dispense at all. The optimal pressure is considered to be around 7 to 9 bars, so make sure you check the needle on your gauge before brewing to see if the setting is right.
Grind Size
The rocks will obviously allow water through much more quickly than the sand. This effect is the same with grind size and espresso. The finer/smaller your grind size, the slower the flow will be. The larger/coarser your grind size, the faster the flow will be.
In order to pull the perfect shot of espresso, you are hoping to achieve an extraction time between 25 - 30 seconds. This can be affected by a number of factors including the grind size and quality of the beans you're using.
There are two main reasons there's no flow coming from your group: a clog or a faulty brew valve. Have you been experiencing anything abnormal before the flow stopped? Low flow would likely indicate a clog, while strange noises would be more indicative of a faulty valve.
If you tamp low-quality coffee grounds too hard, your espresso becomes over-extracted and thus extremely bitter. Besides pressing too hard or too light, a lot of beginning baristas tamp unevenly. While this mistake is underrated, it occurs frequently.
Apply 20-30 pounds of pressure, and polish
Baristas often recommend 30 pounds of pressure, but some do as little as 20 pounds. More and more are finding that tamping pressure is overrated—it's hard on the wrist and cause an over-extracted, bitter brew. Use a twisting motion as you pull up to “polish” the puck.
It takes 10 seconds for an espresso shot to “go bad”. That is, for the heart, body and crema to blend together into a big black bitter mess. If you're drinking espresso straight, it doesn't matter.
The brew ratio we'll follow today is 20g of ground coffee to 30g of liquid espresso. Time ties everything together - the total number of seconds a shot takes. Aim for your shot to pull between 25 and 30 seconds.
The stream of espresso coming out of the portafilter should look something like thick, warm honey. The finished shot should be golden and have a crema thickness of about 1/4" to 1/3".
If your coffee shots are pouring longer or shorter than 35 seconds, your coffee grind needs to be made coarser (larger granules). The space between the coffee grinds in your basket must be altered to allow the right amount of space for water to pass through between 27-35 seconds.
If the coffee comes through too fast, try to grind your coffee finer. If it comes through too slow, grind your coffee a little more coarse and try again.
The rule of thumb with espresso grind size is that the coarser the grind is, the faster it will pull the espresso. What is this? So, if you're looking to slow down the pull of your espresso, then you'll want to change to a finer grind.
The higher the temperature of the water, the more quickly extraction will happen. If water is too cool, extraction takes much longer. At a certain point, some compounds simply won't extract. This is why a cold brew takes much longer and has a much more mellow flavour than a hot brew of the same beans.
For a double shot, grind between 18–21 grams of coffee into your basket. The proper grind is crucial to a balanced, delicious shot of espresso. It might be necessary to adjust its fineness a bit. In general, the grind ought to be quite fine.
It will have a burnt, ashy flavor and may be less palatable than fresh shots; however, they still contain caffeine. The length of time it takes for a shot to 'die' is debated, ranging from ten seconds to three minutes.
The best grind size for espresso is fine. A fine 1/32 size coffee grind will help avoid a sour taste or bitter flavor, over-extraction, or under-extraction. The wrong size can make it hard for the hot water to force through the coffee bed or lead to channeling. This all affects the taste and strength of espresso.
Consuming 20 shots of espresso in a single day is not advisable. Though it is possible to consume up to 400mg (0.014 oz) of caffeine per day, the recommended limit for good health, drinking more than 6 shots of espresso would exceed this amount and can put your health at risk.
If you drink one espresso shot (which has about 50-65 mg of caffeine) and your personal caffeine half-life is about five hours, you'll have a pretty negligible amount of caffeine in your system ten hours after ingestion.
With a slightly curled finger, spread the grounds out so that they are level with the top of the handle's basket. 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.
The ideal level of BAR passing through your coffee grounds should be around 7-11 BARs of pressure, though some espresso machines will be able to hit higher BAR. Machines capable of hitting 9 BARs of pressure will have the ability to produce a rich and concentrated espresso shot.