Heat loss? What heat loss?

So, here’s a confession: I have never measured the temperature of the water I use to brew coffee. Or at least I can’t recall doing so. Yep, it’s true.

I’ll give you a minute to soak that up, throw up your hands, maybe give out a guffaw, delete me from your bookmarks, whatever … … There. All done? Ok, moving on …

It’s not that I don’t have a standard. :30 – :45 off the boil. I think that’s adequate. The emphasis is on repeatability around here, not pinpoint precision accuracy. It’s worked out quite well but this time curiosity got the better of me. Or maybe it was frustration.

In “the lab” this morning I decided to go that “extra mile” and use a thermometer to test the temperature of my brew water in the Buono. This was brought on by a particularly temperamental coffee or, to be more precise, a particularly temperamental flavor I was getting from a particular coffee, a flavor that is obstinate and tenacious in the face of my attempts to avoid it: “burnt”. My first thought was that the water was too hot so I decided to get all scientific on its ass. I don’t call it “the lab” for nothin’

This little experiement was also brought on by an idea that has been floating around, that the Buono is poor at maintaining a consistent water temperature over a brew cycle.

The hypothesis

 By heating the water in the Buono on the stove, as opposed to heating it in another vessel and then transferring it to the Buono, the kettle is material is raised in temperature such that the heat of the metal sustains the temperature of the water inside over an amount of time sufficient to brew a cup of coffee in a Hario V60 or, for that matter, any number of pour-over methods.

The setup

My rig? A small kitchen thermometer – the kind you see in the pockets of chefs all the time – held by a pair of kitchen tongs.

The thermometer was checked for accuracy the way I used to do it back when I worked at Peet’s: fill a cup with ice (really pack it in there), gently fill with water, give it a bit of a stir, place the thermometer in the cup and wait. Give it a few minutes. It should read right around 32º F. If not, it’s time to calibrate. Luckily for me, it was spot on because I have no idea where the plastic calibration wrench that came with the thermometer went.

It was crude setup, I admit but by pure chance, it had at least a couple advantages over simply placing the probe end of a corded remote thermometer into the pot and definitely one over holding it with my bare hand. I’ll let you figure out that last one but as for the other two: because I held it with tongs and because the ends of the tongs were plastic, I was able to keep the thermometer off the sides of the kettle and have some measure of assurance that there was little to no heat transfer from the ends of the tongs to the thermometer itself.

I measured the water temperature at various points along the way toward boiling and also, just for another accuracy check, after the water was at a full boil. Once again, spot on: right around 212º F.

Just as I did for the brew immediately preceding this one, I let the water sit for a full 1:00 off the boil (I had been attempting to cool the water down beyond what it would normally be at :30 – :45 off the boil to get rid of the burnt flavor). The temp? Right around 190º – 195º F.

I started the pre-infusion (AKA, at least around here as “makin’ the bed). It went a little over (≈1:00) because I was busy taking temperature measurements. The temp this time? Again, right around 190º – 195º F.


After the brew was done I took another measurement and again it was right around 190º – 195º F.


This was a full 4:00 off the boil and the water temperature inside the Buono was amazingly stable. Far more stable, in fact, than I have been led to believe I could expect it to be.


The take-away, then? I heat my water on the stove in the Buono – i.e. I’m not simply using it as a transfer pitcher – and am getting an incredibly stable temperature during the brew process and I believe it is because I am heating my water in the kettle on the stove and not using it simply as a transfer pitcher.

A couple questions/issues/blah, blah, blah this brings to my mind:

  • Why is it that in 1:00, right off the boil, the temperature of the water in the kettle came down by about 17º – 22º F but came down no further in the succeeding 3:00? I suspect that holding onto a temperature sufficient to boil water is difficult but that 190º – 195º F is easier to maintain with little to no additional energy input and that temperature plateau would probably be even lower without the insulating effects of the heated kettle.
  • How long does the heated kettle preserve the temperature of the water at the proper brewing temperature i.e. if I wanted a lower water temp for brewing a particular coffee how long would I need to wait? Another experiment, perhaps.

That was fun. I need to do more of these.

Please feel free to add your two cents in the comments.


P.S. I really gotta get on it – I’ve been meaning to create a “My Brewing Parameters” page for some time now.