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The Science of the Espresso

A quick guide to dialing in that perfect shot


We've all been in a coffee shop, patiently waiting for the barista to prepare our drink. Latte, double espresso, or maybe a something a bit more exotic like an iced cinnamon almond milk macchiato. In all, the process seems to be pretty straightforward. Grind the beans, fill the portafilter, pull the shot, then add the additional flavors. That's it right? Well, not quite. Yes, there are some newer machines out there that do a lot of the work for you. However, for those of us not using top of the line $25K espresso machines in a coffee shop, or looking to become a better home barista with a basic machine, here's some tips to ensuring you can still get an amazing espresso shot.

Espresso is all about the extraction of the coffee from finely ground beans, under a high level of pressure. Quality control is very important to ensure the proper extraction.

Control of the grind. Control of the brew ratio. Control of the tamp. Control of the brew time.

Each of these components will ultimately contribute to the end result.


The grind is an important component that will contribute to extraction of the coffee. The grind should be slightly finer than table salt (click here for more about grind size here: A grind that is too fine will result in over-extraction and a more bitter taste. A grind too course results in under-extraction and a more acidic, sour taste. Adjusting the grind of course will lead to a faster, or slower brew. This will be directly related to your brew time to ensure that perfect shot!


The generally accepted ratio for a standard espresso is 1:2. Based on standard accepted sizing, that means a general serving will be 18g of coffee leading to a 32g finished espresso. This leads to a well-balanced, properly extracted cup. For those of us who need more of a kick, you may want to lean more towards "ristretto," with a 1:1 ratio, leading to a darker and heavier dose. On the other hand, a lighter dose of "lungo" generally is the result of a 1:3 ratio. As you work to perfect your espresso shot, these ratios can help you get where you want to be for that perfect extraction. Ever wonder how Europeans can drink 3, 4, or more espressos per day? By revising down the overall amount of coffee used to 10g or less, you too can be an all day espresso drinker. Just don't forget the ratios.


Creating a proper pre-brew "puck" is one more thing you need to consider while prepping your shot. The puck is the dense form of coffee within your portafilter. Why is this critical you may ask? Once you have hit "brew" for your espresso, a high amount of pressure is applied to extract the coffee, much more than a traditional drip cup. By applying pressure with your tamper of choice at 90 deg to the portafilter (look for a good spring-loaded tamper) you ensure a flat, level puck. Baristas will often cite between 20-30 lbs of pressure being the proper application. This will ensure the water being injected through the coffee particles is as evenly applied as possible, contributing to that perfect extraction. Once the coffee has been compressed to the proper density, load your espresso machine immediately and start the brew.


If you are able to get the other variables of your espresso under control, the brew time should come together a bit more naturally. A general target is 25-30 seconds. Longer brew leads to more extraction and strength, with naturally the opposite case for shorter brews. Start with a small food scale under your brew cup, and your finger on your timer. Once you've identified your desired target ratio (1:2 preferably), and you've loaded your portafilter to the 18g weight, begin the brew and start timing. And now for the moment of truth! If you have achieved a high level of precision with the other factors, you have a good chance of nailing the time. Enjoy your espresso as quickly as possible, as it will sour as it cools. Add sugar if needed, but here at Corberosa our Espresso Blend is perfectly delectable as is.


So after all this, your final product is going to come out perfect the first time, correct? We certainly hope so, but if not don't stress! Controlling the numerous factors is an ongoing challenge, and one of the reasons why baristas are coveted for their skills. Aside from the general factors outlined above, some other factors which could impact your overall product include calibration, maintenance, and pre-heating of your machine, as well as water quality. Darker roasted beans (esp Vienna) with more oil will definitely play a factor as well.

You want to minimize the time between grinding your coffee and brewing your espresso. You should be prepared to immediately load your machine and start your brew once you have ground to the desired weight.

You can tell the quality and age of the beans based on the crema in your final product. A general rule of thumb is 10% creme in the final product. When you see an espresso that is a dark black, and no crema that's a tell-tall sign of old beans.

Still looking for some more information? James Hoffman's YouTube series "Understanding Espresso" is a great resource. You can find it at the following link:

We are always looking for feedback,, and recognize there are many other excellent resources out there. Feel free to email us with any other tips and experiences!

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