What water temperature?

 Kettle with custom thermometer

Kettle with custom thermometer

Ask any barista at what temperature coffee should be brewed (in any form) and you'll get a variety of responses - I've heard anywhere from 88 to 97 degrees C (190 to 207 F). Most answers however cluster between 90 and 95 degrees (190 to 203 F). This applies to both espresso and drip/immersion brews. But most of us do not have an espresso machine that can control temperature (like the Breville Oracle - subject of a later review), so this article is mostly about drip (like Chemex or V60) or immersion (like Aeropress) brews, which can be brewed with a relatively cheap kitchen thermometer. The following are some general tips.

  • Between 90 and 95 degrees C (190-203 F) is 'about right'. The most frequently cited temperatures are 92-93 degrees C (198-200 F). However, there is a significant number of baristas that like cooler at 90 C (190 F) or hotter at 95 C (203 F), and outliers that will recommend 88 or 97 degrees C (190-207 F). Do not stray further than these outliers. You'll find that much colder than 88 C (190 F) and your coffee will be underextracted and too sour/acidic, and hotter than 97 (207 F) and you risk scalding it and not extracting precious flavour notes, leaving your coffee with a flat, bland flavour.
  • You can estimate temperature with time. When boiling about 1L of water, waiting for 60 seconds post-boil will bring the temperature down to the right area. Of course this depends greatly on environmental factors and your kettle (i.e. its insulation effectiveness, which translates to a conductive coefficient in physical terms). In general, if at all possible, I would recommend getting a simple thermometer as a priority.
  • Hotter brews emphasise bitterness, sweetness and body, whereas cooler brews emphasise acidity. Sweetness and body being positive attributes, the idea of cooling a brew temperature is to reduce bitterness while not allowing acidity to overwhelm the cup. Thus, a naturally acidic ('bright') roast/bean might favour a hotter brew, as a cooler brew will allow acidity to overwhelm. However, a roast/bean that lacks acidity can be brewed cooler and still be quite pleasant.
  • Manage the cooling period. Depending on the kettle you have and the amount of water boiled, water will inevitably cool as you pour it. If you have a small, thin-walled pouring kettle, then your brew may cool by 10 degrees C (or even 20 F) or more during the pour.

In general I would always suggest experimenting with brews and seeing what works at different points along the spectrum, trying them in an immersion brew (where temperature is easiest to control) and documenting the results, then applying those results to whatever brewing method you use.