Coffee Shots & "The God Shot"
Understanding Shots and Ratios and Recipes has been a real education journey!
On the one hand you have coffee ratios which refer the ratio of ground coffee weight at the start of a dose, to the liquid weight of brew extracted.
Coffee strength is measured in Total Dissolved Solids (TDS) and is usually marked as percentages (%). These are the soluble solids part of the brew which is is the actual physical amount of coffee dissolved and pulled out of the dose by the water.
Understanding how important ratios are and understanding how they affect the taste of the final brew, became much more apparent when refractometers started to be used to understand the effect that altering those ratios, had, on the TDS being extracted and the resulting Yield.
For a more in-depth look at TDS and Yield, check out the article "What is TDS in coffee and how to measure strength of coffee?" by jori-korhonen
Ratios were used to help explain the differences between common coffee extraction recipes such as Ristretto's, Espresso's and Lungo's and the like.
A "Ristretto" a.k.a. "restricted" shot is usually considered to have a ratio of 1: 1
e.g. 7g coffee in for 7g brew out
... or be within the 1: 1 to 1: 1.5 ratio (Some sites say this ratio should result in "anything over 12%" TDS while others offer a range such as 30~40% TDS along with the resulting 82~60% of water making up the shot)
A "Normale" a.k.a. also referred to as a "single / regular / normale / espresso"
is a standard "shot" considered to have a ratio of 1: 2
e.g. 7g coffee in for 14g brew out (30ml or 1 liquid oz)
... or be somewhere within the 1: 1.5 to 1: 2.5 ratio (Some sites say this ratio should result in 8~12% TDS while others say 10~20% TDS along with the remaining 92~80% water)
Note: a "Doppio" a.k.a. "double" is simply a double shot espresso with a traditional double-shot being a 17g dose for 34g out.
For a good explanation, check out 'The Real Prometheus' video "ESPRESSO ANATOMY - The Double Shot" from 3:12 to 4:02
A "Lungo" a.k.a. "long" is usually considered to have a ratio of 1: 3
... with anything in the 1: 2.5 to 1: 4+ ratio considered acceptable (Some sites say this ratio should be 2~8% others say 6~8% TDS along with the remaining 98~92% water)
Side-note for filter coffee, the TDS should lie in the range of 1.15% ~ 1.35% or even 1.9% for mild / light coffee roasts.
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Lets quickly re-cap the key espresso extraction elements to save looking them up again:
Dose: The amount of ground coffee you start with
e.g. 18 grams for a double-espresso
Ratio: How much water gets pushed through the coffee dose
e.g. 36 grams for a double-espresso
Grind: Coarseness / Fineness - used to control flow rate within the 25~30sec to achieve
desired brew weight and get close to a good taste.
If taste is sour, grind finer.
If taste is bitter or harsh or puck is channeling, grind coarser
Special Note: We also discovered that while it is widely and commonly accepted that grinding finer increases the exposed surface area of coffee and therefor allows increased extraction, a scientific study titled "Systematically Improving Espresso: Insights from Mathematical Modeling and Experiment" published in the Matter journal has proven that this is NOT entirely accurate!
For a great explanation of this study, we suggest you watch James Hoffmann's excellent video "Did Science Just Reinvent Espresso?"
The pertinent summary occurs between 1:28 and 4:04 minutes into the video.
Temperature: of espresso brewing water.
85~90°C (185~194°F) for darker roasts
88~92°C (190~198°F) medium espresso roasts
and 90~95°C (194~203°F) for lighter espresso roasts
Pressure: of the water being produced by a pump to apply consistently to each dose
within the group-head, typically 9 bars (9 atmospheres or approx. 130 psi.)
is considered a sweet-spot for most espresso machines.
Flow: Is the resulting output of pressure
Time: Typically 25~30 sec,
28~30 secs for a slow extraction such as when using an extra 1/2 gram to fine-tune
(dial-in) the taste, rather than playing with grind density.
Another Special Note: following the above discovery on grind density vs extraction, there are growing reports of places doing things like 16g in for 30g out with 15 second brew times using only 5 ~ 6 bars of pressure, and getting excellent results!
There is no "correct" ratio, its all about preference of taste.
What ratios do is provide a common starting point from which to experiment and develop our preferred brews.
We also need to be aware that ratios differ depending on the brew extraction method.
Coffee extraction falls broadly into one of two methods;
1. percolation where water passes through a bed of coffee - think pour-over;
BTW: for a good read on making pour-over coffees, try Scott Rao's excellent book "Everything But Espresso"
2. infusion (also called immersion) where all the water and all the coffee intermingle for the whole brew-time - think French Press
Some common starting ratios are
60grams per litre of water for percolation brewing
Note 1: While espresso is technically a form of "percolation", the extraction is done using water at high pressure and temperature, so the espresso starting point is
16 grams coffee for 32 grams of extracted brew for a double-espresso shot
A Rule-of-thumb: Typically you would use a little more coffee for infusion than for percolation.
75 grams per litre of water for infusion brewing
Note 2: With the Aeropress infusion design you can choose either a strong short brew, or a regular coffee. For a regular cup, the above ratio is a good starting point, while for a stronger brew you could start with 100 grams per litre
You should only alter the ratio once you are happy with the taste.
If you brew a delicious tasting coffee but wish it was just a little stronger (more body), that is when you do change the ratio. If the brew is a bit tasteless, bitter or sour, don't alter the ratio, change the extraction and get that right first. Grind finer (bearing in mind the "Special Note" above) or steep-longer/extract-slower or even agitate more for infusion brews, to better mix the grinds with the water.
Now to add a bit of healthy confusion we also have shot measures!
On the one hand you have the "standard" measure and on the other the more recent "Third Wave" movement
You also have people talking in mixed-units citing metric grams (g) of coffee and imperial ounces (oz) of brew as well as those whom use grams-in and grams-out
All quite confusing to the newbie!
Further, the problem with ratios is that they do not account for all the other many variables which make up a delectable drink of coffee:
The design, quality and adjustability of the espresso machines;
The size and quality of the espresso machines filter baskets;
The barista's skill at pulling the required shot;
Grinder type and quality;
Where and how the beans were grown with variables such as altitude, temperature, sun/shade, soil, etc;
The bean roasting profiles (the darker the roast the easier to extract the solubles);
How the beans were harvested and processed;
How the beans were stored both pre and post roasting.
Most research will tell you that a traditionally brewed espresso shot was about 7 grams of finely ground coffee extracted into 1- liquid ounce(oz) of brew [there's those damn mixed-unit measures!] otherwise measured as 28~30 millilitres (ml). Hence the idea of approx. a 30 ml "shot" of extracted coffee.
And while 7g single shots were the "standard measure", the more popular serving size is the modern double-shot
We've already been told that espresso should have a ground-coffee to delivered-brew ratio of 1: 2 (... or at-least be within the range of 1: 1.5 to 1: 2.5)
Now math may not be a strong point, but a 1: 2 ratio means for every 1 in, there should be 2 out, so for 7 (grams of ground coffee) in there should be ... 14 grams of beverage out ... NOT 28~30ml
Now before we get further buried in the minutia of ratios, lets just recognise that ratios on their own are NOT the simple "how to make a perfect coffee" answer that we might all wish for, but if we really want to understand this stuff, lets dig a little deeper.
So we turned to our go-to source of all-things-coffee - Mr James Hoffman the author of
The World Atlas of Coffee and creator of a number of excellent videos which include:
He makes a number of excellent points including that its a damn-awful practice to use mixed-unit ratios! Why would you mix metric and imperial measures such as 7g of coffee to brew 1oz of drink! NO! That's a very bad and confusing approach to start with!
Stick to ONE type of measure and it's immediately easier ... grams-in, grams-out or at-least (milli-)litres if we must use volume as our output measure.
James goes on to explain that the whole concept of a fixed ratio of coffee-to-brew is also not that "fixed", due to other variables involved with brewing the coffee (as noted above).
"Typically" about 1/3 of coffee is soluble (around 28% typically) i.e. These are the parts of the physical coffee bean which can be dissolved with water and extracted as the coffee brew we drink. The rest will never dissolve and they make up the "grounds" which we discard. BUT ... that percentage does vary depending on the type of bean, where it was grown and how it was roasted.
Additionally, the temperature and pressure of the water used to extract the 'nectar' from the coffee, and in the case of espresso, even the way it was tamped into the the group-head basket, all impact on the resultant brew strength and flavour, regardless of the ratio of coffee-to-extracted-brew.
So James (and others ) make the point is that there is no "correct" ratio because he resultant brew is really all about how each individual prefers his or her coffee strength.
Ratios are (to coin a phrase from "Pirates of the Carribean") "more of a guideline really".
They are the starting-points which the majority of coffee consumers would consider their "Ristretto", "Espresso" or "Long" coffees to be pleasantly acceptable to drink.
However, we still haven't really answered the question of how an acceptable espresso ratio of 1:2 works out to be 7g in to 28ml out!
The short answer is, ... it doesn't !
In his video, James paid homage to Andy Schecter and his great contributions to the coffee community via the Home Barista forum, including his detailed explanation of coffee ratios in relation to the various coffee brew styles.
Andy points out that all the variables we mentioned above (and more) all influence the amount of crema produced and this can cause the measured volume of a shot to vary significantly. The only accurate way to measure the actual total amount of espresso produced (combined 'Heart', 'Body' and 'Crema') is by weighing it, NOT by measuring it volumetrically.
This photo shows the difference between volume (35ml) and weight (25g) of the same brew just because of the crema.
If you had said you pulled a 35ml brew you'd be wrong ... from an extraction ratio perspective. When the crema all fades away there will be close to 25ml of brew.
So there you have it ... use weight-in vs weight-out and avoid the confusion.
Using weight over volume provides far more accurate and repeatable variables which is key to achieving "successful" espresso recipes.
Single baskets are generally designed for dosing 7-9g coffee; double baskets for 14-18g.
If you want to dose higher, there are triple baskets designed for 21-24g.
A Rule-of-thumb: Lighter roasts - use the lower end of dose weight
With a lighter roast coffee you have to work much harder to extract it, so using a big dose of light-roast coffee requires a lot of work and can often wind up as weak, sour, harsh, under-extracted and lacking body. Generally the darker the roast the easier it is to extract from, so you can afford to use the upper end of dose weight
Playing with pressure and flow
There is a raft of information relating to pressure and flow which we may summarise in another post, but for the moment we'll just touch on the following significant points.
Again James Hoffmann has a good video on this topic if you want more information.
Pressure is an input to an espresso recipe while flow is the output of that. Understanding the output and how to control the input to get the output that makes the best coffee, is the key to working with pressure control.
Pre-infusion in various forms, is used to promote more even extraction when the full pressure is applied to the puck to perform full extraction.
9 bars produces about the 'peak-flow' for most espresso machines before flow starts to decrease due to puck compression.
The higher the pressure, the more likely channels will form through the puck, resulting in localised over-extraction and resulting bitterness.
Channeling becomes more likely toward the end of extraction, so there are machines which allow a step-down in pressure toward the end of the extraction process.
The higher the pressure the finer you can grind ... up to the point at which channeling and/or compaction occurs in the puck.
Using a lower pressure, say 6 bars, with a slightly coarser grind can sometimes produce a better tasting shot because of a more even extraction throughout the whole bed of coffee in the puck.
Playing with Brew temperature
The only other thing to expand upon a little in this post is regarding brew temperature.
How temperature affects taste.
Refer above for the typical ballpark temperature ranges for various roast profiles.
Adjusting temperature should just be another variable which can be 'tweaked' a tiny bit.
Understanding that increasing the temperature will increase extraction, you could make incremental (or decremental) adjustments of at-least 1°C each time, to tweak the taste, but only after playing with ratios and recipes.
Lets say you're left with slightly sour or acidic taste after altering ratios and grind/flow, you could then try increasing the temperature a degree or two to see if the increase in extraction offsets that acidity. Likewise, if after all else there remains a repeated bitterness, you could try dropping the temperature a degree or two.
The God Shot
So now we come to the perfect or "god shot" of coffee.
The "God shot" started out as a description for that espresso shot which a true barista might manage once in every few hundred pulls ... if they are lucky!
At best it is an objective description of a 10/10 espresso (only) coffee shot, using the absolute best of the best of everything! Perfect conditions, perfect equipment, perfect barista (if there is such a being) and planets in full alignment.
Using an A-class espresso machine, high-quality espresso coffee beans correctly prepared, stored and shipped, a top-tier grinder, pure well-balanced water, correct temperature and pressure of extraction with no channeling. The equipment needs to be set up by a pro and the pull must be done by someone who knows exactly what they’re doing.
Even then, the reality is that its a subjective assessment of how good a coffee pull tastes to the palate of each drinker.
The "god shot" should be an incentive in pursuit of becoming a better and better barista but is should not become a negative aspiration where your shots are never quite good enough that you wind up becoming frustrated and wasteful of what is probably already a heavenly-brew ... to others palates.