Coffee brewing variables
And alternatively, how NOT to brew.
Brewing the perfect cup of coffee may sound quite subjective, but it's actually quite easy if you have good brewing habits and good supplies.
We all prefer different flavors, roast levels, types of beans, brew strength, and additives (black, cream, sugar, etc.). All of this and more can be achieved in what we'll call the "perfect brew". Here we use the word "perfect" to describe ideal extractions and making the most (or getting the most) quality out of our equipment and supply.
Don't be overwhelmed by the many variables used to set a brew recipe: Brew Ratio, Time, Temperature, Turbulence, Grind, Pressure and Filtration. We'll cover these in turn, but just as important we should cover those things you should NOT do in order to get a perfect repeatable cup of coffee.
First, the 5 Commandments - Do NOT brew this!
- Do NOT randomize your brew time.
- Do NOT vary your water temperature.
- Do NOT randomly grind coffee more coarse or fine.
- Do NOT use dirty coffee equipment.
- Do NOT think that water is water and that it really doesn't matter.
In turn, the 5 Commandments - DO brew this.
- Plan a brew time that aligns with the brewing device.
- Stick with water temps between 90-96° C (195-210° F.)
- Grind your coffee to match the brewer you select.
- Clean your coffee equipment and give it a hot rinse before using it.
- Make sure your water is good, odor free, not too hard or soft. Good water in gives you the chance to get good coffee out.
A fine combination of art and science
The science of brewing doesn't change. Hot water must engage coffee grounds to be absorbed so that the water may dissolve the coffee matter. Perhaps that dissolved (extracted) coffee is caught and cleansed by a filter.
The art of brewing should also not change. Just as a painter applies methodical brush strokes and a pianist stays within a boundary of selected scales - so too your handcraft elements of dosing, pouring, timing and temperature should stay consistent within certain boundaries.
So how do you know where to start and how do you build those good habits from the beginning? Or, how do you recognize what bad habits you may have that should be broken?
Coffee : Water = The brew ratio
The Specialty Coffee Association recommends a brew ratio (which directly impacts the strength of your coffee) at 50g-60g of coffee per liter of water (1,000ml). For the Imperial US standard of measurement that is about 2 oz of coffee to 34 oz of water. There is no good way to convert the mass of 60g coffee to the volume of a scooper, but for simplicity that's about 12 level tablespoons for 1 liter of water.
Unlike Metric units which correlate mass (weight) and volume (liquid) closely, the US Imperial measures entirely confuse mass and volume. Yet, if you have no gram scale in your kitchen you can build some simple cheats and measures that work within these ratios. (hint: there are 3.78L / gallon so if you need an easy measure you could use about 4 tablespoons for 1 quart of water)
Coffee tastes best when it is brewed between 1:15 and 1:17 (coffee:water).
AKA 1g of coffee to 16g water.
The above ratio falls at: 1,000ml / 60g = 16.67 (or 1:16.67 brew ratio).
If you use much more than 1,000ml water for the same 55g of coffee, you will have a weaker (less strong) and possibly over-extracted cup of coffee. You may have extracted (dissolved) too much from the coffee grounds. The later stages of extraction may taste more woody and bitter.
If you use much less than 1,000ml water for the same 55g of coffee, you will likely have a strong and under-extracted cup of coffee. In this situation you have extracted (dissolved) too little from the coffee grounds to taste balanced and good. Your cup may be marked by sour or sharp flavors.
Coffee grind size and extraction
Some people wrongly think, "if I grind the coffee finer then it will be stronger and last longer." This is wrong for a number of reasons. Coffee grind size is not about flavor or efficiency - but rather it is a prescription of the brew method chosen. As a rule of thumb, follow these guidelines.
- Turkish (powder fine) grind for an Ibrik or Turkish brewer. Think powdered sugar.
- An espresso machine requires a very fine espresso-style grind. Think fine salt.
- A moka pot or Aeropress should should be ground fine like sand.
- A home auto-dripper, pour over, V60 and syphon should be ground medium like sugar granules or sea salt.
- A Chemex or Able Kone should be medium coarse like corn meal.
- A French Press and Toddy cold brewer should be coarse like golden sugar crystals.
The reason we don't use espresso grind in a french press is because all other variables are fixed in the french press. We wait 4-5 minutes and then plunge a metal filter through the coffee and water in a French Press. The temperature, turbulence, filter, time... everything is prescribed, so the grind should match. If you put espresso grind into the french press the coffee comes out muddy, cloudy, over extracted and unpleasant. The fine espresso grinds will seep past the metal filtration and present a very bitter cup.
Likewise if we put espresso ground fine coffee into a home brewer, the natural flow of water through the paper filter will clog. The time will go much too long. The machine may over flow and spill out onto the kitchen counter. The coffee flavors will be muddled and over extracted - this is altogether unpleasant.
Rules of thumb:
- Finer ground coffee extracts (dissolves) easier and requires less time - coarse ground extracts slower and requires more time.
- Hotter water extracts coffee faster - cooler water extracts more slowly.
- Turbulence (stirring) increases the rate of extraction.
- Pressure applied increases the rate of extraction.
- When time is extended for coffee to water contact, extraction increases.
By understanding the direct and indirect relationships above you can increase or decrease your coffee concentration (brew ratio) to find your preferred coffee taste.
Start with a brew ratio of 1:15 - 1:16 - 1:17
1:15 is stronger (less water = more concentrated)
1:17 is lighter (more water = less concentrated)
You may even find that you enjoy a 14 or 18.
Experiment!
Grind size must follow brew device.
Keep time & temperature fixed for consistency.
Filters and roast impacts on brewing
Over the ages, various filtration mediums have been used to filter grounds from coffee. Metal, cloth, and paper are the most commonly used. Metal will allow various coffee oils to pass easily or entirely into the brewed beverage. This creates a thicker body and more clouded flavors/aromas to the brew. Cloth and paper will yield a clean cup of coffee absorbing both oils and ultra fine dissolved coffee particles from the brew. This reduces the coffee body slightly but also increases the clarity (flavor perception) and cleanness (sweet acidity) of the brew.
However, all filters should be clean. Cloth should be cleaned well between uses since it is reusable. Paper is best when rinsed beforehand in order to remove any papery or cardboard like aromas and residues. Likewise, metal filters should be washed and wiped clean of oils which can easily become rancid and bitter if not cleaned properly.
Your goal is to brew a perfect consistent cup.
You can set a brew plan and prepare the stage!
It is worth repeating:
- Plan a brew time that aligns with the brewing device.
- Stick with water temps between 90-96° C (195-210° F.)
- Grind your coffee to match the brewer you select.
- Clean your coffee equipment and give it a hot rinse before using it.
- Make sure your water is good, odor free, not too hard or soft. Good water in gives you the chance to get good coffee out.
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