If you don’t have a kettle with temperature indication, the answer is probably yes. I previously followed guidance that I found on the internet of brewing coffee 30 seconds off the boil. My coffee, in many cases, would have bitter and astringent qualities that I didn’t taste at my local café. After a few years of struggling with bad tasting coffee, much to the bemoan of my wife, I finally found out that the water I was using was too hot.
For my kettle, which is a gooseneck Bonavita without temperature indication, 30 seconds off the boil will still result in a water temperature of 211 degrees. Pouring this directly onto the coffee will inevitably lead to bitter off-flavors. Now, I use water no more than 205 degrees. This means stopping the kettle early, waiting longer after the boil, or even adding an ice-cube to the kettle on the occasional impatient morning. To avoid losing thermal momentum during the brew, I will thoroughly heat up my brewer with hot water. In my v60, the slurry temperature will only lose 1 to 2 degrees during the brew process using this method.
. If you’re coffee is overly bitter, try dropping the temperature and see if the taste improves. With light roasts, 205 F is a great place to start. For darker roasted coffee, try 195 F to 200 F. Of course, experiment, taste, and let us know how it goes!