Avoid any coffeemaker with a hot plate that continues to apply heat to the coffee. After more than 15 minutes’ exposure to direct heat, your coffee changes chemical structure, and all kinds of bitter, acrid compounds emerge.
Use clean, fresh water.
Coffee is 98% water, so it is essential to use clean, fresh water for proper extraction. You may need to filter your water to reduce impurities, and if your water is extremely hard, or you have old plumbing that gives it an “unpleasant” flavor, use bottled water.
Water should always be freshly drawn and never re-boiled. Hot water pulled from the tap or water that’s boiled for a long time becomes deoxygenated, the result is a cup that’s flat, lacking clarity and acidity.
Use the correct water temperature.
Unfortunately, most auto-drip coffee makers do not heat water to the correct temperature. If your coffee is under extracted, you probably need to replace your brewer or use a pour-over or immersion method to brew.
For brewing coffee, the proper water temperature is between 195-205°F. If your water is too hot, you will scald the coffee and produce bitterness from over-extraction. If the water is not hot enough, the result will be under-extraction and result in sour, bitter flavors and a thin, watery consistency. As a rule of thumb, you will be close to the correct temperature if you pause a moment after the water comes to a boil. If you are after perfection, use a thermometer.
For pour-over or other manual brewing methods, it’s best to use water that’s on the hotter side, try to keep the coffee slurry at about 200°F. It’s also important to remember to preheat the brewing equipment to ensure proper heat retention during the brew cycle.
Measure your coffee and water every time.
There is only one way to ensure consistent brewing results. Use a scale. Preferably a metric scale. By weight, the water-to-coffee ratio should be between 15:1 and 18:1 depending on desired brew strength. If you insist on winging it, that’s roughly two tablespoons of coffee per 6 oz. of water.
Start with fresh roasted whole bean coffee.
Once it’s roasted, coffee is sensitive to air, moisture, heat, and light. Keep your whole-bean coffee in an air-tight, opaque container at room temperature. Set your grinder for the brew method you are using and only grind the amount of coffee needed for the next brew-cycle. Grind too fine, and you will have a bitter and over-extracted cup. Too coarse, the results will be watery and under-extracted.
Only brew what you plan to drink.
Many volatile aromatics and flavor compounds in brewed coffee will dissipate in a short period of time. For the most satisfying experience, consume your coffee within 20 minutes of brewing.