"Dialing In" a coffee for espresso can be both a precise skill and an art form.  It typically stems from years' of experience, benefiting the speed at which it's done, or how many (few) changes need to be made.  Efficiently and confidently working through this process is very important to the home user that isn't pulling hundreds of shots a day with an unlimited supply of coffee.  As with anything food/cooking related, there are numerous ways this can be done, but hopefully by walking you through my workflow, things I think about or note, and supplementing a few resources along the way, it can expedite your learning curve.  

The Coffee

I always start by thinking about what kind of coffee I'm using and what trends or tendencies the particular coffee may have including:

• Is it a single origin coffee or a blend?  Roasters will tend to roast single origin coffees lighter to showcase that coffee's terroir or the origin's traits.  And typically speaking, lighter roasted coffee requires a finer grind, particularly for espresso.  Blends tend to be more forgiving than single origins since the particle distribution will be a little more homogeneous with different coffees and some origins or processing methods are more forgiving than others, creating a little forgiveness factor.  Blends may also have a little more developed roast profile, which will allow them to be more forgiving and necessitate a coarser grind.  
  • If it's a single origin, how is it processed and where is it from?  Processing method can also play a role as natural or dry process coffees tend to be more forgiving and require a coarser grind than washed or wet process coffees.  This again is a generalization, but typically washed coffees require better distribution and prep skills and a finer grind.  
  • Certain origins (and varietals within that origin) tend to require finer or coarser grind as well.  I tend to find some African coffees, particularly Kenyans, need a very fine grind setting for espresso.  Whereas washed Colombian coffees may not need a grind setting any finer than a naturally processed Ethiopian.  This again depends on the roaster, the varietal and the origin.  
  • Without getting too deep into varietals, I tend to (vastly) generalize it like this:  large bean size varietals or coffees that feel "softer" tend to need a coarser grind than small sized beans and coffees that feel hard, like little stones.  
• You've probably already caught on but the roaster and how the coffee is roasted plays a huge role in this.  The same coffee can be roasted to two different levels that would necessitate two different grind settings.  Generally speaking, darker roasted coffee (within reason, not Charbucks dark) will need a coarser grind than lighter roasted coffee.  
  • Some roasters have a reputation or label their roast profiles as well.  For example, a roaster like Counter Culture or Mountain Air believes all coffees should be developed enough to be brewed by any method.  #AnyCoffeeAnyBrew.  Whereas some roasters will roast with a brewing method in mind.  49th Parallel will sometimes offer the same coffee at two different roast levels for filter and for espresso.

Control Your Variables

It's always going to be easiest to control and manipulate the coffee when you limit your variables, and know what they are.  To do just that, you should:

• Know how much coffee you're dosing into the portafilter basket to the tenth of a gram using a digital scale.
• Prepare the coffee in a consistent manner each time; dosing, distributing, tamping, as consistently as possible.
• Use a bottomless portafilter so you can watch your extraction - this is more technique and prep related but I do find I can better watch how the coffee is extracting.  I can see when the first beads form, how fast or slow the coffee is flowing, and when it blondes.  
• Watch your shot.  This is one of the most important reasons why I use a bottomless portafilter; so you can identify the blonding point.  At some point (assuming you're in the ballpark for your grind setting to begin with) the water has extracted all it can from the water and there is a visual change in the stream.  The stream of coffee gets thinner, runnier looking, and lighter in color, or goes blonde.  This is the blonding point.  With practice, you will begin to identify when this is about to happen to be able to cut the shots right before they hit the blonding point.  After the coffee reaches this point, you are diluting your beverage by adding more water, that is generally over extracted, since all of the solubles have been extracted from the dose.  Some styles of coffee and espresso shots work well going past the blonding point, but identifying this and how it effects flavor is important.
  • This article, "Barista Technique: Good Extraction, Good Espresso" does a nice job explaining why and how to end an extraction by color.  
  • "Photos of Common Espresso Problems - Perfecting the Naked Extraction" provides a good visual to what is being discussed and what you can learn by using a bottomless portafilter.
• Time your shot, note how long the shot ran when you cut it off at the blonding point.  Although, I find shot time to be the least important factor, it's one less variable or one more control to monitor how things are changing.  Even if a coffee tastes great, but maybe you're curious about how pulling it differently might change it, knowing the time is useful.  
  • For example, if you're using a coffee that has great balance, body, mouthfeel, and viscosity but maybe you want to see if you can bring out more acidity or fruit and floral qualities, you know you want to keep the brew ratio, or the proportion of the dose to the final beverage weight relatively the same, but speed up the extraction by making the grind coarser. 
  • For reference, I start the timer when the pump is activated.  Any preinfusion is counted as happening before the shot. 
• Weigh your output.  This provides your brew ratio, such that if you dose 18 grams of coffee into the portafilter and your final beverage yield is 36 grams, your brew ratio is 1:2 or about traditional normale range.  If you decrease the ratio or say pull a shot to 18 grams in to 28 grams out, the shot becomes tighter or ristretto.  If you increase your yield to say 42 grams, the shot becomes a lungo.  

Evaluate and Adjust

Now evaluate what just happened both from a data standpoint and more importantly, by taste.  Starting strictly with data, we know in general a double espresso shot should be a 1:1 - 1:3 brew ratio in about 25 - 30 seconds.  Given the styles of coffee you use and the shots your prefer, I would even make that window even more liberal and say time could be between 23 and 40 seconds.  Notice, I did not reference beverage volume; the liquid volume of the beverage can vary greatly in mass, making it another variable, and also doesn't make much sense to switch units when we are weighing the dose (mass).  

This tells us that if the first drops of coffee hit the cup almost immediately, went blonde at 14 seconds, with a beverage weight of 38 grams, the grind was way too coarse, the shot ran too fast, and the coffee is going to be very under-extracted, sour, and acrid.  A shot that ran like this would probably go straight in the drain with a dramatic grind change (finer) to follow.

Provided your shot ran around the general window of espresso extraction, the next step is to taste it.  After all, delicious espresso is what this is all about.  If you're lucky, you just pulled a banger and you can enjoy it and be on your way.  Assuming additional dial in is needed, developing the skill to do so by taste is an invaluable barista skill.  If you are new to espresso or this process, I highly recommend you start by reading (home) espresso guru, Jim Schulman's, "Espresso 101: How to Adjust Dose and Grind Setting by Taste" over at Home-Barista.com.  The following two charts are from that post, and I include both, because I find they compliment each other and that reading the same information presented in different ways develops a deeper understanding.  

Jim Schulman's guide is super helpful in thinking through the process by controlling variables, and even selecting an approach to do so.  As you develop your skills, you can modify the process to your own almost instinctively.  Being that a majority of the coffees I use are single origin and lighter and brighter, I tend to stick to the 18 gram VST basket, which typically doses well with an 18 gram dose, regardless of the coffee density.  It may need a slight manipulation in dose here and there, but in general my dose is almost always the same.  

Because of this, when I'm dialing in a coffee by taste, I'm mainly paying attention to the yield and the time.  I know I said time is probably the least important variable, but I'm not thinking of it as a parameter but rather a reading or data.  I think of the time as the extraction, or that increasing shot time, increases extraction.  I can't take credit for this line of thinking, as the Espresso Compass by Barista extraordinaire, Matt Perger and Barista Hustle lays it all out there.  I started using this chart identifying the actual adjectives as guides, and I still consult it from time to time when I'm puzzled, but I now find myself using the tips and the overall graph as the guide to manipulating the coffee.  

Putting it into Action

This week's coffee for #whatsCTpulling inspired this topic and serves as a great example of an outlier coffee and my thought process of working with it.  Kenya Gachatha AB from Kuma Coffee is a lightly roasted, washed Kenyan coffee that has the visual characteristics that it would need a fine grind.  The coffee I was using before this was roasted darker, was a "softer" feeling bean, and was being pulled through the IMS Precision Double baskets, which require a coarser grind than VST filter baskets.  I chose to use the VST basket, because it was a lightly roasted single origin coffee, and I had heard from others that Kuma does lightly roasted coffee very well, so I should be able to really work to maximizing the extraction, which is exactly what VST baskets are designed to do.  

So, I adjusted my grinder finer, dosed 18 grams into the 18 gram VST filter basket, and went through my typical prep routine.  The shot pulled very slow and tight, first drops didn't hit the cup until around 10 seconds after pump activation.  The final extraction was 18 grams in to 29 grams out in about 42 seconds, and it was delicious!  The coffee tasted like homemade cherry syrup or a rich grenadine with a hint of floral spice.  I then looked at the tasting notes on the bag to see "cherry candy" and "jasmine" as two listed...boom!

I pulled another shot a few hours later with the same settings and parameters with equally delicious results.  However, being that this shot was pulled so tight, and these were my first two pulls, I decided to see what would happen if I sped up the extraction a little.  Would I get more brightness and start to see the Watermelon and Currant flavors listed on the bag come forth?  Would the cherry syrup give way to a fruit punch medley with juicy acidity?  So, I adjusted the grinder coarser to try and decrease the extraction, and increase the yield.  This is typically the opposite of the way you would usually go, since the goal is usually to maximize the extraction, but I thought this reverse look at it would supplement the charts and information linked above.  

By coarsening the grind, the shot ran faster, which by the charts above, should decrease any bitter flavors / highlight or bring forward more sour/acidic characteristics, or by the Espresso Compass, decrease extraction.  A by product of this was the yield did increase slightly as well to about 35 grams, which weakens the coffee, which in this case I wasn't concerned about since the initial 18:29 gram ratio is quite dense and concentrated.  I continued this process trying shots at 35 seconds and 30 seconds.  

These faster shots, though still drinkable and sweet, lost their oomph that really wow'ed me to begin with.  The balanced acidity of previous was cranked up, and the coffee was losing the syrupy sweetness, bordering on more astringent grapefruit notes.  The cherry syrup went away in favor or more of the watermelon and grapefruit like flavors that don't really showcase how good this coffee really is.  

I ended up taking this coffee back to where I started with a very tight and slow flow and low yield, which opened up the "sweet spot" on the Espresso Compass.  Improving and increasing the extraction to these lengths can be common for lightly roasted single origin coffees.  So, what I'm hoping this showed is that you should really let your palette be the judge and make the most delicious tasting coffee possible.  Think through  what you're tasting and what you would want to change, and then think through how the shot was pulled and which variable(s) need changing to take you in the right direction.  With practice, this will all kind of take place simultaneously, and you may even be able to start manipulating multiple variables at once.  

Between the main articles linked in this post (all bold font is almost always linked), and the underlying concepts of these charts, you will begin to identify immediately what needs to happen based on what you're tasting.  This post is certainly not the end all be all, and that's part of what makes coffee so fun.  I am hoping that it helped gather some various resources, elaborate on the process, and supplement some of the basic principles found in the Coffee section of the website, and in the other Improving Espresso posts, which will be ongoing.  

There's a lot here, so if you have any questions, comments, suggestions, or care to discuss, please contact me or leave a comment below!  

Thanks for reading.