First, you will create a recipe.
Recipe # 1: "Traditional" Espresso
“Traditional” espresso is pulled close to a 1:2 coffee:water ratio. I would only recommend this for Octane or Monolith, because these coffees are chocolaty and tend to work well with higher strengths. These two coffees are typically darker roasted, which mutes some of the innate acidity found in the green coffees we source for these blends.
Typical “Traditional” Espresso Recipe:
20 grams of dry coffee
40 grams output of liquid
time: 25-33 seconds
Recipe #2: "New Wave" Espresso
“New Wave” espresso is pulled closer to 1:2.25 or 1:2.5 (I've also seen 1:3+) and tends to dilute the solution compared to "Traditional" recipes. I tend to take this approach for single origin coffees from Ethiopia, Kenya, and Colombia. These higher acidity coffees tend to be more balanced with a more dilute presentation because they can be too intense are higher concentrations.
Typical “New Wave” Espresso Recipe:
20 grams of dry coffee
45-50 grams output of liquid
time: 23-33 seconds
Second, you will make slight adjustments to get your coffee within optimal ranges.
What things can I change?
Change your grind size
Under normal assumptions a finer grind size will make the coffee Extraction % go up, and increase the strength or TDS %. With coarser settings, Extraction % will go down, and strength or TDS% will go down. Grind size surface area has a direct relationship with both TDS % and EXT %
Change your brew ratio
Using more coffee per gram of water will increase your strength or TDS % and decrease your Extraction %. Similarly, using less coffee per gram of water will decrease your strength or TDS% and increase your Extraction %.
Brew ratio has a direct relationship with TDS% and an inverse relationship with EXT%
How to Troubleshoot:
Always rely on grind adjustments first.
1.) Your coffee tastes sour and salty. This is likely under extracted coffee and I would try to grind finer and see if it fixes the problem.
2.) Your coffee tasted bitter and astringent. This is likely over extracted and I would try to grind coarser and see if it fixes the problem.
Always rely on brew ratio adjustments second.
1.) Your coffee tastes weak and looks like tea or dirty water. This is likely too weak and you need to use more coffee per gram of water.
2.) Your coffee tastes too strong and seems much too intense. This is likely too strong and you need to use less coffee per gram of water.
I rely on grind adjustments first because I want to manipulate one variable at a time to see the impact it has on the system. With grind adjustments, you are maintaining the same brew recipe and the same brew ratio, which makes tracking differences in time and it's relationship with TDS% and EXT% much easier.
I rely on brew ratio adjustments second because you are effectively creating a new recipe(a new brew curve, more on that later), which means you will have to again make adjustments to your grind size to get things balanced.