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Topic: Adjustments for altitude (3 msgs / 108 lines)
1) From: James Pratt
Howdy!
     First post on this list, but I must say that I'm impressed with the steady volume of traffic I've seen for the past few days; it make another list I'm on (w/ something over 1000 members) seem like pikers; you guys must have even less of a life than me! I did a bit of a search of the list's archives, and didn't see anything over the past few months, so here goes: I live in Colorado Springs (elevation roughly 6000 feet), and this seems to make a difference in both roasting and preparation for me - I end up using somewhat (5-10 degrees lower) temperatures on my i-Roast than Tom's recommended profile, generally (though I tend to use a somewhat higher "warm-up temperature", usually 355 but sometimes higher than that. Second stage is usually 390-395, and 3rd stage is usually in the 420-430 range, depending on what I'm going for; if I use 395 for a second stage, I'll hear a few early first cracks after around 2 minutes (I'm usually using 2:30). Presumably this is due to the low
 er boiling point of water at this altitude, around 202 F. Does anyone know if there's a similar shift for second crack? I'm guessing so, since I'll get into second crack (I think - can't really hear it, what with the noise the blower makes and my tinnitus - but it sure seems to look and taste like it!) after around 3 minutes at 430. I've been toying with the idea of raising the second stage up to around 410, which should give a fairly slow-developing first crack but probably not reach second, to allow me to do a slower roast than I've been doing when I want more chocolate notes and less brightness, possibly combined with a 425 or 420 3rd stage, for when I want to get to FC+ (or higher, if I want to get beyond it). Any thoughts on this?
      Also, I was reading at the SM site about the new Technivorm drip makers, which prompted me to find a review of one on-line. It looks like at this altitude, it's probably going to be a wee bit cooler than one (or the SCAA, anyway) might like, unless one insulated the "arm" at the top of the machine that delivers water from the reservoir to the filter. (This is a guess, based on how much drop people are getting at lower elevations.) I have friends who live up around 9000 feet (boiling point, about 196 F) who'd have even more problems, too, but even here, it seems the only chance I have of getting coffee brewed "correctly" is either 1) with a vacuum pot (and probably then only by pushing the water up a lot quicker than you'd want to, at lower elevations) or 2) using a press (my normal method of late), with water taken all the way to boiling, then added to it. (If it weren't a lot of extra hassle, I'd want to preheat the press, as well; it's a vacuum-insulated stainless one
 , with a little bit of thermal mass to it, but I REALLY don't relish the idea of boiling 2 pots' worth of water, using the first to preheat, and also having to then empty it to add the ground coffee before the second pot-full. Instead, I just use somewhat more coffee, and/or extract a little longer. I do transfer to a Thermos afterwards, though, to keep from over-extraction.) All and all, I can't complain too much about the results, but I bet that if I was going for as good a cup of espresso as possible (on a machine that has it), I'd probably have to make pressurstat adjustments (among other things), too... Anyone done any research on this? 
     Well, that's probably way more than enough questions! You should probably hope I don't post too often!
                     James

2) From: petzul
Hi James,
Am I correct in thinking that boiling point of water depends on vapor 
pressure, and the vapor pressure decreases with altitude therefore it 
takes less temperature to boil. A thermostat should function the same as =
long as you are staying below the boiling point. 190F is 190F is 190F.
All that said, I am not sure how hot the Technivorm makes its water. Is 
it hotter than the boiling point at your altitude? If not you should not =
have a problem.
Hope this helps,
PeterZ
Roasting at 1200 ft above sea level, here in LHC (I am up on a hill here =
)  :)
James Pratt wrote:
<Snip>
 steady volume of traffic I've seen for the past few days; it make anothe=
r list I'm on (w/ something over 1000 members) seem like pikers; you guys=
 must have even less of a life than me! I did a bit of a search of the li=
st's archives, and didn't see anything over the past few months, so here =
goes: I live in Colorado Springs (elevation roughly 6000 feet), and this =
seems to make a difference in both roasting and preparation for me - I en=
d up using somewhat (5-10 degrees lower) temperatures on my i-Roast than =
Tom's recommended profile, generally (though I tend to use a somewhat hig=
her "warm-up temperature", usually 355 but sometimes higher than that. Se=
cond stage is usually 390-395, and 3rd stage is usually in the 420-430 ra=
nge, depending on what I'm going for; if I use 395 for a second stage, I'=
ll hear a few early first cracks after around 2 minutes (I'm usually usin=
g 2:30). Presumably this is due to the low
<Snip>
now if there's a similar shift for second crack? I'm guessing so, since I=
'll get into second crack (I think - can't really hear it, what with the =
noise the blower makes and my tinnitus - but it sure seems to look and ta=
ste like it!) after around 3 minutes at 430. I've been toying with the id=
ea of raising the second stage up to around 410, which should give a fair=
ly slow-developing first crack but probably not reach second, to allow me=
 to do a slower roast than I've been doing when I want more chocolate not=
es and less brightness, possibly combined with a 425 or 420 3rd stage, fo=
r when I want to get to FC+ (or higher, if I want to get beyond it). Any =
thoughts on this?
<Snip>
akers, which prompted me to find a review of one on-line. It looks like a=
t this altitude, it's probably going to be a wee bit cooler than one (or =
the SCAA, anyway) might like, unless one insulated the "arm" at the top o=
f the machine that delivers water from the reservoir to the filter. (This=
 is a guess, based on how much drop people are getting at lower elevation=
s.) I have friends who live up around 9000 feet (boiling point, about 196=
 F) who'd have even more problems, too, but even here, it seems the only =
chance I have of getting coffee brewed "correctly" is either 1) with a va=
cuum pot (and probably then only by pushing the water up a lot quicker th=
an you'd want to, at lower elevations) or 2) using a press (my normal met=
hod of late), with water taken all the way to boiling, then added to it. =
(If it weren't a lot of extra hassle, I'd want to preheat the press, as w=
ell; it's a vacuum-insulated stainless one
<Snip>
e idea of boiling 2 pots' worth of water, using the first to preheat, and=
 also having to then empty it to add the ground coffee before the second =
pot-full. Instead, I just use somewhat more coffee, and/or extract a litt=
le longer. I do transfer to a Thermos afterwards, though, to keep from ov=
er-extraction.) All and all, I can't complain too much about the results,=
 but I bet that if I was going for as good a cup of espresso as possible =
(on a machine that has it), I'd probably have to make pressurstat adjustm=
ents (among other things), too... Anyone done any research on this? 
<Snip>
obably hope I don't post too often!
<Snip>
cribes) go tohttp://sweetmarias.com/maillistinfo.html#personalsettings<Snip>

3) From: James Pratt
<Snip>
Yes, if I remember my physics (or was it high school chemistry?) correctly.
<Snip>
Definitely true.
<Snip>
Well, I don't have a problem with it - I don't own one of them! And looking at the pictures I saw in a coffeegeek review, it doesn't look like they're likely to have a problem with explosion or anything like that - it looks like they use steam pressure to push the water up and over to the filter basket. sort of like a vacuum coffee maker. What I'm curious about with them is whether or not it makes much (if any) difference in how the coffee tastes. I mean, it might well be that the same forces that make for a lower boiling point might also make for better extraction at lower temperatures. I thought about this because of homebrewing (beer), oddly enough: for some varieties of mashing, I end up adding boiling water to my mash (mixture of malted barley and warm water) to raise its temperature, and I have to use more of it to get the same "step" in temperature. Also, to sterilize some "premixes" for brewing, I want a higher pressure on my pressure cooker, to get to the same temper
 atures. (Fortunately, that higher pressure is well within the safety limit of the cooker!)
At any rate, beyond a certain elevation (I'd guess around 10000 feet), I suspect it's impossible to reach the SCAA lower limit, without a pressure greater than the ambient one. 
OTOH, there are so many other ways to screw things up that I guess I shouldn't be surprised that I have never had an even halfway decent cup on an airliner; considering what most of them serve for food, it should be even less of a surprise! (And to think that it was an old college roommate, now an airline pilot, who got me into home-roasting...)
                              James


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