How does high altitude affect brewing? - Page 2

Beginner and pro baristas share tips and tricks for making espresso.
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#11: Post by HB »

another_jim wrote:Doing this very accurately is expensive; but for this purpose, cheap will do just fine - an inexpensive thermocouple up the spout of the PF will tell you what you need to know.
I wondered if Eric's thermocouple adaptor would be helpful, even if you used a type K sheathed TC and a cheap multimeter. OK, it's probably a little overkill...

Dan Kehn


#12: Post by mteahan »

All the speculation about boiling temperatures at altitude and the effect on extraction is missing the point. The water temperature of the boiler is not affected at all by altitude.

Nada, Zero, Zip.

Can I be more clear than that?

The only argument that could be made is that the water leaving the group at a temperature above the boiling point at altitude would vaporise the water upon contact with the outside air. However, once the pressure in the portafilter chamber hits 0.5 bar, even that argument goes away as the pressure would compel any water that WANTED to transform itself into a gas would be prevented from doing so.

If the operation of the boiler in heating water was somehow determined by the boiling point of water, then altitude could make a difference, but it doesn't.

"This is not the droid you are looking for"
Michael Teahan
analogue | coffee

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#13: Post by HB »

mteahan wrote:All the speculation about boiling temperatures at altitude and the effect on extraction is missing the point. The water temperature of the boiler is not affected at all by altitude... Can I be more clear than that?
Sorry, did I miss something? While you, Jim, Ken, and I haven't said it the same way, I believe we are all in complete agreement.
Dan Kehn


#14: Post by mteahan »

You might be right. I suspect the conversation has moved to the water temp as it exits the group, which I addressed in the second part of the post.

The espresso leaving the portafilter will not be at a temperature above the boiling point of water at altitude.
Michael Teahan
analogue | coffee


#15: Post by bruce »

Wouldn't the dissolved solids in the espresso raise its boiling point above that of pure water?

Matthew Brinski

#16: Post by Matthew Brinski »

I have been really biting my tongue on replying to this thread. I also have a Vetrano and a Macap just as you. Furthermore, I live at 8,500 feet. I will tell you that you can get really decent shots at this elevation, in my opinion. I have had a few cups that left me saying "Damn, that was REALLY good!" Having said that, I have also had a lot of bad shots. The reason I have been reluctant to reply is that I don't know if I have found the best routine for brewing at this altitude, and I want to relay a somewhat quantified and systematic approach to you.

My current practice consists of:

1. I flush the group while listening to it without the PF (I usually flush while simultaneously distributing and tamping), and cut the pump just as the audible
boiling/hissing fades out. I have learned through practicing some group flushes that the "hissing" returns at 25 - 30 seconds after the group flush which
I presume is the onset of boiling water at the local boiling point (approximately 196 - 197F). To avoid brewing with boiling water, I start my extraction
at 25 seconds after the stop point of the group flush so that I am brewing with as high of a temp water that is possible without boiling.

2. I pull a restricted double (mine are usually 1.25 to 1.5 oz) in a range of 24 - 28 seconds. I pull a double ristretto based on the learned theory (thanks to
Jim Schulman on your awesome article) that the bitters will balance out the initial acids/sours that are more prominent in a low temp extraction - at
least, this is the way I have understood and experienced it thus far.

3. If I experience trouble with acidity with certain blends, I'll sometimes cut the initial 1 - 3 seconds of the shot (let it go into the drip tray). I really don't
like to depend on that approach though. I feel as if I'm robbing the potential of the shot as a whole.

I have been trying to experiment some with letting the HX rebound longer than my normal interval to increase extraction temp. The problem with this is that I have no idea what temp I'm extracting at.

It's been mentioned by some (people who have coffee knowledge many levels above mine) that local boiling temp is not a concern due to the brew water being under pressure. I totally understand the concept. My issue with this though is that when I let my hx rebound longer, the shots can taste burnt or bitter. Is this due to the initial infusion that is boiling water (you can hear it during the initial extraction)? Is this due to the rebound being too long with the temp getting too high? I don't know. Furthermore, I have had more hit and miss shot consistency with channeling while extracting with the brew temp being above boiling. I think that the initial "gassing" infusion of brew water compromises the integrity of the prepared puck. Maybe there's something I can do to correct this through my technique - I don't know.

Speaking of technique, if you don't have a bottomless pf, I would encourage you to get one. I prefer spouted pf's, but my bottomless was INVALUABLE in self training my dosing, distribution, and tamping. If those aspects of your technique aren't consistent, neither will the taste of your extractions, regardless of a stable and proper brew temp.

Anyway, I have been sticking to my 25 second routine lately due to the amount of guessing that goes into other approaches. I have a Scace on order, and I will do A LOT of experimenting when I get it. Hopefully, I'll be able to relay a flush/temp control routine after I get some hard data that correlates to good extractions. My data logger is going to be busy.

Matthew Brinski

mtnwoman (original poster)

#17: Post by mtnwoman (original poster) »


I'm glad you stopped biting your tongue!! I'm excited to find someone else who has the same set-up as I do. At the very least we need to share notes...either in this forum of via email! I'd love to know how you have your grinder set, what beans you are experimenting with, etc.

It sounds like you are doing some version of "flush-and-go" as Dan has recommended. I plan on trying this with my next shots.

I did get my bottomless portafilter yesterday and pulled one hurried shot this morning. I think my tamping is spot-on, but I still need to fiddle with the dosing to get the timing of the shot closer to 25 seconds.

I really appreciate all of the good advice this newbie is getting from the seasoned folks!

Espresso Smith

#18: Post by Espresso Smith »

"It's all in the cup" I have always said this and I continue to say it.

You have all mentioned that the temperature/pressure in the boiler is not affected by the altitude - this is true.
However, the water boiling temperature will affect the extraction of the espresso (the most common problem is the flash of boiling water and steam towards the end of the extraction, which destroys the crema).
Boiler pressure/temperature will affect water brew temperature and group temperature.
I read more than 10 posts on this forum from people that have high altitude problems with their espresso extraction.
Why are temperature sensors being installed directly on the group heads?
Because there is a direct relation between the boiler pressure/temperature, the group head temperature and the water brewing temperature.
Without going into all of the details of thermosyphoning, heat transfer, heat exchangers, group head mass, preinfusion, etc. there definitely is a challenge in extracting excellent espresso at high altitude! The 9 bar pump pressure/1.2 -1.4 bar boiler pressure/18-22 second extraction time should be erased from the espresso machine manuals.
I have tasted wonderful espresso extracted at 16 seconds and at 45 seconds.
The boiler pressure, pump pressure extraction time will change from location to location, machine to machine, and from espresso blend to espresso blend. Again - It's all in the cup!

If you find that at 8 bars of pump pressure, 0.9 bar boiler pressure at 30 seconds - the espresso tastes "out of this world" then that is how you need to extract your espresso.
At high altitudes, due to the problem of boiling points, you need more time to extract the espresso. This requires slightly lower pump pressure, slightly lower boiler pressure and longer extraction time. This is achieved easier by using a lighter roast of beans and working with the elements (water, boiler pressure/temperature, pump pressure, grind - and even messing around with the thermosyphon), to create the profile you are looking for.
I make a living making sure that my customer's blend profiles taste the same whether in Denver (5280 ft. elevation), Breckenridge or Aspen (8,000 - 10,000 ft. elevation), and beg to differ with anyone who claims there is no problem extracting espresso in high altitude.

Espresso Smith Inc.

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#19: Post by hbuchtel »

Espresso Smith wrote:"It's all in the cup" I have always said this and I continue to say it.
Great, you are in good company!


Matthew Brinski

#20: Post by Matthew Brinski »


I'm glad you jumped in on this. I REALLY want to experiment with pump pressures and extraction times/volumes (and I have already to a certain degree), but I'm waiting for a Scace device to arrive so I can correlate brew temperature to the other variables. I want to know the specifics of what works not only to make repeatable extractions, but also to make an attempt of actually understanding the hows and whys of what works well. One thing that you mentioned that I have found to be true through experience is the use of a lower pump pressure. I am currently having best success with 8.5 bar. I am also having greater success with pulling restricted shots. I have had good shots up to 40 seconds (triple basket at 1.5 ounces), but lately have been sticking around 28 seconds (using both ridged and ridgeless double baskets at 1.25 - 1.5 ounces).

Something that I'm curious about is whether or not the actual extraction process at the coffee grind itself behaves differently at high altitudes. I would guess not, but I have no idea.

Matthew Brinski

PS - Can you recommend any places in Breck that pull decent shots? I have experienced nominal at best in just about every town in this state, with exception to a couple shops in Denver and Boulder.