I recently switched from a Bonavita electric kettle to the Stagg EKG 0.6L, with an Aeropress. Before trying the Stagg, I matched the water temperature inside both with a Fluke thermometer to check the accuracy of the displays. I then brewed the same coffee with both kettles, and tasted. To my surprise the coffee from the Stagg came out way worse- underextracted.

I found that the water coming out of the Stagg's spout was almost 5 degrees cooler than from the Bonavita, even though the water inside the two was the same temp. It turns out that at idle, the water in the spout is (unsurprisingly) much cooler than it is inside the kettles which the display is showing.

The Stagg's spout is smaller in diameter than the Bonavita, and it seems to lose more heat in the spout at idle and during the pour. Another factor seems to be that the Stagg takes longer to fill the Aeropress and does not agitate the grinds as much during the pour. Both lead to underextraction.

So I ended up plugging the spout in the Stagg and pouring right out of the top into the Aeropress. Problem solved, taste was good again.

It's possible that one could avoid most of the temperature shift by first pouring into the sink to clear the cool water from the spout. But that still leaves me with a slow pour with no agitation for the Aeropress. (For pourover that may be a good thing.) Stagg now makes a kettle with just a lip spout instead of a gooseneck, which would likely work fine for my purposes.

Bottom line(s)-

- A precise display of the wrong thing can throw you a curveball.

- After many trials with consistent technique, I found the taste of a 1 degree shift is consistently noticeable, and 2 degrees is significant - roughly equivalent to 1 click on my Virtuoso. The Stagg with its PID is able to hold +/-1F; if you surf it, even better.

Disclaimer, as these days seems to be necessary: I am only a retail customer, no connections.

cpreston wrote:After many trials with consistent technique, I found the taste of a 1 degree shift is consistently noticeable, and 2 degrees is significant

That's extremely difficult to believe, given the myriad variables in play. Just for starters, tasting a cup dripped at 200F (say), then tasting a second one 5 minutes later dripped at 201F---the odds are infinitesimal that the two cups are 1 degree apart when they hit your taste buds.

Why not figure out how hot to get the water in the new kettle to get it the same out the spout?

wsfarrell wrote:That's extremely difficult to believe, given the myriad variables in play. Just for starters, tasting a cup dripped at 200F (say), then tasting a second one 5 minutes later dripped at 201F---the odds are infinitesimal that the two cups are 1 degree apart when they hit your taste buds.

I make them hours apart and taste each at the same temp. I go back and forth many times. Definitely not blind or direct a/b but after many trials with several coffees I am convinced. But in order to see it you do have to hold the technique very constant. Nonetheless of course YMMV. And possibly not true of pourover which is harder to repeat.

I found the taste of a 1 degree shift is consistently noticeable

I disagree

I can definitely notice a difference with two degrees F in the flavor of coffee with my Behmor BraZen which is very temperature stable. I tend to drop the temp for coffee from Ethiopia and dark roasts and recently forgot to do this with an Ethiopia so I had a recent occasion for comparison.

Maybe there's a way to purge the water in the spout back into the kettle to mix the water temps a bit with some air pressure from a syringe, baster, or even the Giotto rocket blaster that some use for clearing grinders from stray grounds.

BTW maybe I should explain a little more about how this came about... I was trying to see what I needed to do, within reason, to get a more consistent cup. My experience has been that making very good coffee is not so hard, but making it taste exactly the same every time is hard.

For reasons of consistency I have stayed mostly with immersion brewing, first with a Clever and now, because I like a dense cup, an Aeropress. I drink only one cup at a time.

Here's how I experimented using the Stagg. Every morning I made two cups, maybe an hour or two apart, during which time the brewer cooled back down. To hit my temperature I would wait for the kettle temp display to just tick downwards to my test temp, then use the Aeropress the same way each time.

For the second cup of the morning I would adjust the temperature either up or down a degree or two, and again wait for the temp to tick downwards to the new temp, first raising it above target if necessary (surfing). That way I made sure that the reading was not off by an extra degree. OK, very fussy... but it did seem to make the results clearer.

Some days I made the hotter cup first, and other days I made the cooler cup first. I did this for weeks, through several coffees. Almost every time I felt that the taste went detectably in the direction of the temperature... lower temperature-more acid/sour, higher- more bland/bitter. All of the cups were good, but one of the two was almost always preferable.

So, no, nowhere near a blind test. But the taste results seemed so consistent for many cups over several weeks that I have become convinced. As a cross check, I tried adjusting the Virtuoso to match the effects of the temperature, and as I mentioned, it seemed like 1 click was roughly equivalent to 2 degrees.

Not science, and I'm not trying press the point. But I feel it has given me more consistent coffee with the Aeropress.

That is interesting about your experience with the Stagg 0.6L. I recently switched from the Bonavita temp-control to the Stagg EKG (the regular, 0.9L). I have not experienced a difference at all in taste at the same temperature setting, and do not seem to have the same issue of the water in the spout being different in temp to the water in the body of the kettle. Of course, I haven't precisely measured, and if there is a difference in temp within the kettle, it must be similar to the 1L Bonavita for the 0.9L EKG model. It sounds like there might be a design flaw with the 0.6L model, and I would say you should at the very least inform Fellow of this so they can test it or perhaps inform you if it is atypical. Is the spout on the 0.6L much thinner in inner diameter? I wonder if that is affecting it.

As far as taste being different between 1-2° F difference, I agree. I think that if you're looking for a difference and tasting to test that, you'll see one, at least with lighter roasted coffees or coffees with more aromatics. I don't think that it is a significant enough difference for anyone blindly served to notice it unexpectedly. I do think 5° would be very obvious to anyone, however, if they are familiar with that coffee. This is of course only if the rest of your variables are consistent enough to not cause variation in taste themselves.

Yes, I can't really explain it. But an accurate thermometer did show that the water inside the Stagg and the Bonavita were at the same temperature. Although even there it's a bit tricky because it depends on how far in you insert the probe.

Also I am pouring out only a small amount of water to fill the Aeropress. For larger brews the initial cool spout may make less difference.

Would it help if you poured out the first 100 ml or so from the Stagg to warm up the spout before pouring into your aeropress? Or maybe insulate the spout of the Stagg?