I’m : a programmer, writer, podcaster, geek, and coffee enthusiast.

On reheating coffee


Marco is answering coffee questions today, so perhaps he can clear something up for me. Microwaving coffee. Good, bad, or horrible?


I just need to add a bit of heat, so I’ll frequently throw the mug of coffee in the microwave for thirty seconds. It fixes the temperature problem, but from my unscientific observation, it significantly degrades the flavor. Am I imagining this? Why does it happen? Is it really doing something to the coffee’s flavor or is it just that my conception of great coffee is so antithetical to my conception of something that comes out of the microwave that I feel I’ve committed some sort of sin against propriety and project this guilt onto my tastebuds?

Microwaving coffee makes it taste very bad, quickly and conveniently. I still do it when desperate, but I’ve found a better way.

The best way to have hot coffee over many hours, without re-making it every time you want some, is to thermally insulate it so you don’t need to reheat it.

My preferred way to achieve this is the 117-year-old technology embodied by the simple Thermos vacuum bottle. Get the largest one that you’ll want to fill on a regular basis. The Thermos Nissan briefcase-bottle lineup is great:

When you make coffee, pour the amount you want to drink right now, then immediately pour the rest into a nice Thermos bottle and close it. (By the way, I’m referring to Thermos Nissan as the brand, not as the generic, diluted term of calling all vacuum bottles “thermoses”. Thermos Nissan’s products are top-notch. Get the best.)

It will stay hot for about 6-8 hours and acceptably warm for at least 4 hours after that. And that’s with the smallest bottle, not being full the whole time. The bigger the liquid volume, the longer it stays hot.

It’s not a perfect solution: one problem is that the metal is slightly porous, so it imparts a slight metallic taste to the coffee. It’s relatively minor for the first few hours, and gets stronger as the day goes on. The effect gets weaker as the Thermos gets older, and you can accelerate the aging process a bit when you first get it by filling it up with boiling water and leaving it for a few hours. This would probably be alleviated with a glass-lined bottle, if you can find a good one and don’t plan on dropping it.