The Denver effect?

Beginner and pro baristas share tips and tricks.
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shadowfax

#1: Post by shadowfax »

So, I remember reading about this as something that David Schomer complained about some time ago, but that it turned out to be something altogether different from the lower pressure, because, of course, at 9 bar, it doesn't matter that the boiling temperature is lower at 7320 feet above sea level--it's still way, way over brew temperature.

True.

But with any machine with preinfusion, there's a ramp-up. You start out with the water just sort of flowing onto the coffee. My concern is, it seems like this very initial bit is leaving me with spots of burned crema and tainted shots.

Most of the shots I have been pulling, I flush between 4-7 oz; haven't tried more than that yet, as the shots do begin to get sour at 6-7 oz, though again it's mixed with a burnt taste when I sip the dark part of the crema off. Again, my shots are pouring beautifully, it's just that it seems no matter how long I flush, I get a patch of very dark brown in my otherwise pretty golden crema.

Does anyone have experience pulling shots up this high? The boiling point is like 197.2-198.2 here, depending on the weather, much lower than at somewhat lower elevations (temperature is logarithmically related to pressure, I believe). Is there some other common mistake I could be making that would lead to brown patches like I am getting?

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malachi

#2: Post by malachi »

I've never worked that high, but I ran a coffee bar at about 5k feet elevation and it was really challenging. A higher elevation still seems like it would be a nightmare.

We found that it was key to stick with beans that preferred a lower brew temp, run at a slightly lower pressure, flush very thoroughly and pull short shots.

My experience was that the "window" you have to work within (where all the variables align) was much, much smaller than at lower elevations.

All that being said... it was, in fact, possible to pull great shots.
"Taste is the only morality." -- John Ruskin

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shadowfax

#3: Post by shadowfax »

Do you have any recommendations for some good low brew temp preferring blends that I can get over the internet?

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malachi

#4: Post by malachi »

Try Black Cat as a starting point.
"Taste is the only morality." -- John Ruskin

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shadowfax

#5: Post by shadowfax »

Hrm, I looked at black cat, and I'm not in the mood to dump the money for their 2nd day shipping. Maybe some other time... I ordered some more Caffe Fresco Daterra's reserve, which Anthony recommends a range of 198-201 on. Also got some Ethiopia Harrar, which he also recommended a low temp on. That should be interesting.

At any rate, just to followup, Dan deemed my post on what I think could really be going on as new-thread-worthy, so I thought I'd link to it in here: Uneven Extraction.