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Topic: Vac pots and elevation (14 msgs / 597 lines)
1) From: Bill
This is me being anal-retentive, but curious if anyone has any thoughts
about vacuum brewing at higher elevations.  I live in Cheyenne, WY,
elevation 6062 ft.
Someone posted a link recently to a calculator for computing the temperature
of boiling water based on elevation and barometric pressure.  The link was:http://twoloonscoffee.com/map/boiling_point.phpOne thing that was mentioned was about vac pot brewing.  It said: "Vac pots,
or vacuum brewers, or balance brewers, don't rely on boiling directly, but
on vapor pressure. The process of boiling is by definition inextricably
linked with vapor pressure, so if you have a vac pot that brews at 200F =
at
sea level, it'll be brewing at 191F. when you move to Denver. You might
want to grind a little finer, and let the coffee stay up north a little
longer to compensate for the cooler brew temp."
I have only had a vac brewer for a week and I'm enjoying it quite a bit.
 And I should point out that I can't notice any deficiencies in the coffee
flavor.  But my question is: is there any way to increase the temp for
brewing to be "optimal", 195-200F?
I've searched the forums at CG and have done some google searches but I
haven't found anything that would answer this question.  I have been playing
with a thermometer and it seems that my temps are only hitting 190...  Mark
Prince at CG just did a how-to on siphon brewing and wrote: "If you leave
the siphon coffee maker long enough, eventually the top vessel water
temperatures will reach 100C, but this takes a very hot heat source and five
or more minutes of brewing time in most cases."  I have kept the vac pot on
heat for over 5 minutes but have not gotten temps to get higher than 190 F.
 That's just pure water, no coffee, to try to see if I could make it hotter.
Any thoughts?  My thought is that I shouldn't worry too much about the temp
of the water, that I should just enjoy the coffee that I'm getting from my
Yama.  But this is the detail-obsessed curiosity that has me wondering.  Any
input is appreciated.
Thanks in advance.
Bill in cheyenne
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2) From: raymanowen
I've thought about this myself.
Without heating and brewing taking place in a pressurized container like the
espresso machine, the temperature is totally limited by the atmospheric
(absolute barometric) pressure.
Actually, lacking an adequate valve body and pump construction, the brewing
water will be at atmospheric pressure unless the pump is actually operating.
Not the boiler's jacket pressure.
I don't know how they're built, so it's just a thought.
Cheers, Mabuhay -RayO, aka Opa!
Got Grinder?
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3) From: Paul Helbert
If I lived at your elevation I'd be experimenting with making a
pressure lid for my vacuum pot. Could start as simple as a flap of
inner tube rubber with a book for weight. Remove for the push down
phase. Look at old pressure cookers: It doesn't take much to add half
an atmosphere, and you don't need even that much.
That or add enough salt to your water to raise the boiling point.
-- 
Paul Helbert
Prepackaged, roasted & ground coffee,,,
Some of the worst ideas since sliced bread.
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4) From: Rich
I don't think that salt will  improve the resultant taste of the coffee.
The risk of a nice pleasant steam explosion complete with flying glass =
could be the result of placing a book on the top of the coffee pot and =
heating.  I would not  do it.  Adjust the grind and/or the extraction =
time.  The water will be very close to 201F
30 in. Hg: 212.15 F or 100 C (at approx sea level)
29 in. Hg: 210.3 F or 99.06 C (at approx 1000 ft or 305 m above sea l=
evel)
28 in. Hg: 208.44 F or 98.02 C (at approx 2000 ft or 610 m above sea =
level)
27 in. Hg: 206.59 F or 96.99 C (at approx 3000 ft or 914 m above sea =
level)
25 in. Hg: 202.89 F or 94.94 C (at approx 5000 ft or 1524 m above sea =
level)
23 in. Hg: 199.19 F or 92.88 C (at approx 7000 ft or 2134 m above sea =
level)
Paul Helbert wrote:
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5) From: Bill
I agree that salt probably wouldn't be what I'm looking for in all of this
coffee obsession...
Rich, I think that you provided boiling points.  The only thing that I've
found about vac pots at elevation I've put in the original post...  The
person who wrote that seems to indicate the vac pots are dependent on
atmospheric pressure, not boiling point...  Because water boils here at
200F, +/- 1 degree... so it's perfect initial temp for a french press...
So I'm curious about 2 things: does anyone know if the statement in the
original post is correct, that vac pots will work at lower temps at
elevation (a few tests that I've conducted indicate that 190 is about the
hottest I could get with the vac)?  2nd, are there any work-arounds that
would make the water in the top container hotter?
Thanks for all the input!  I'm hoping for some stuff that will really make
me think about this stuff...
bill in wyo
ps someone on coffeegeek recommended salt in coffee water as well... that's
funny to me!
On Mon, May 26, 2008 at 8:22 AM, Rich  wrote:
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6) From: webviking6
Bill,
I'm just outside of Denver at 5400 feet and I have the same concerns =
about water temperature that you do.
In any case, while I agree that vac pots don't rely directly on boiling =
water, but vapor pressure to achieve their brew pressure, there's =
something that you may not have considered.  Think about a typical vac =
pot with a lower heating chamber and a tube going up to a brew chamber =
on top.  The brew chamber is open to the air and thus at whatever the =
surrounding atmospheric pressure is.  In order for the water to get =
pushed up to the brew chamber, the pressure inside the heating chamber =
obviously has to be greater than the surrounding atmospheric pressure, =
whatever that is, right?  And that pressure increase also raises the =
boiling point of water in the heating chamber.  And it also =
correspondingly increases the temperature required to increase the vapor =
pressure enough to push the water up the tube. =
All you need to do to increase the temperature of the water hitting the =
brew chamber is increase the height of the tube between the two =
chambers.  A higher column of water to push requires a higher pressure =
to do the pushing.  And higher pressure in the heating chamber means a =
higher boiling point for the water in the heating chamber.  You'd want =
to insulate your tube, but it seems to me with a little experimentation =
you could come up with something that delivers perfectly heated water to =
your brew chamber.  You'd have to be a little bit careful, because if =
the water hitting your brew chamber is higher than the boiling point for =
water at whatever the barometric pressure is that day, it would flash =
into steam, and you'd end up with an indoor geyser.  Of course a =
Wyomingian?  Wyomingite? err... feller from Wyoming like yourself knows =
all about geysers, lol.
Ha!  If you had a flexible tube and a ring stand you could check the =
barometric pressure and raise or lower the brew chamber accordingly =
right before you brew.  People might look at you strangely, but hey, you =
can get used to that.  What's really important is the coffee!
LOL
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7) From: Ben Salinas
Bill,
What is your vacpot process?  How long do you leave the water in the bottom
chamber before sealing the top chamber in place?
I generally aim for 91C (but I sometimes go as low as 89C or as high as 93C,
depending on the coffee).  I find that if I leave the water in the bottom
chamber too long, I can get my water to be near boiling (I've gotten
temperatures as high as 98C in the top chamber).  But then again, I am at
sea level. So one thing you might try is not putting the top chamber in
until the water is fully boiling.  Putting the lid as the water is traveling
up would also help.  This should let you get your maximum temperature
possible.
As for the temperature relating to elevation.  If I understand the process
correctly, the elevation will dictate a maximum temperature for your top
chamber, but shouldn't dictate a minimum.  This could mean that if you
live too high, you might not be able to get a high enough temperature to
fully extract the coffee.  That being said, I wouldn't be surprised if you
could get something around 91C or 92C (with a bit of work), which is what
I prefer to brew at anyway.  I'm able to brew within 1-2C of my boiling
point (if I wanted to), so I wouldn't be surprised if you could as well.
All this talk about elevation makes me wonder about another method of
brewing.  One of the really nice things about a vac pot is the ability to
brew at a flat temperature over the entire extraction (which isn't the case
in a French Press or a pourover). I've heard about the "Cowboy" method of
brewing coffee, which was basically tossing some grounds into a pot of
boiling water.  This is bad for 2 reasons- 1) the water would be too hot and
burn the coffee and 2) the turbulence in the water would cause the coffee to
overextract.
I'm wondering what would happen if we were to hold a pot of water at just
below boiling at 7000ft and toss some coffee in (perhaps in a tea ball).
I don't necessarily expect the results to be fantastic, but it'd be an
interesting experiment.
On 5/26/08, Bill  wrote:
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8) From: Rich Adams

9) From: raymanowen
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10) From: Dean De Crisce
I wonder if the ideal brew temp is a function of the thermometer reading...=
or actually a function of the water's temp in relation to its boiling point=
 (a little less than boiling...whatever that is at). E.g. If you were on to=
p of Mt Everest and the water boiled at 170 (for argument sake)...the fact =
is that it is boiling hot and it may be the molecular process of boiling th=
at is too "hot" to brew.
Any chemists or physicists out there?
Dean De Crisce
Sent from a Treo phone.

11) From: Bill
Rich,
had been using week-old coffee for the last few days.  Today used
fresh-roasted coffee.  Like, 5 hours old... Anyway, it bloomed like crazy
and made a mess over my entire stove!!!  I should have predicted it, I was
just asleep at the switch.  So far, I haven't had a problem with the
bloom...
bill in wyo
On Mon, May 26, 2008 at 10:59 AM, Rich Adams  wrote:
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12) From: Bill
Ben,
great question.  you made me think.  I would love to hear other owners of
vac pots to chime in on their experiences.  I HAVE noticed that the vac pot
will send coffee north before it's boiling.  And if I boil it on the stove,
it'll go absolutely nuts in the upper chamber.
Here's my technique.  Give me feedback on what I can tweak.
I boil the water, turn on the electric burner to medium on my stove.  Pour
boiling water into the yama pot (a bit over the 5 cup line), dry bottom if
needed, put on burner on wire grid.  Wait until water is acting hot... I've
been playing with different variables lately.  But in general, I wait until
I see 1 big bubble come up, turn off the burner, put in the upper pot, grind
coffee, dump into upper pot, stir, steep 2 minutes, pull off heat.  kick
down takes too long, like 3 minutes.  am considering wet towel to wrap
around bottom chamber...
So anyway, what I'm realizing is that if I let the water boil in the lower
container, it would be hotter when it goes north.  Question: I use a glass
cona rod to filter... when I really get hot water in the bottom container,
it kicks the glass rod around a lot, making me worry about grounds in the
cup.  Can I let the bubbling subside in the top before I put the coffee in?
In answer to your second question about cowboy coffee... I'd seen some info
that cowboy coffee works great at elevation.  I hadn't thought about the
agitation provided by the boiling, as you wrote, but great thought.  But
yes, if water boils here at 200 F, that's perfect for extraction.  Sea
level, the water would indeed burn the coffee, but not at elevation.  I
heard that someone filters it through a swissgold filter after making cowboy
coffee...  Anyway, that might be a pretty useful experiment, I'll have to
try it sometime.
Still interested in feedback regarding vac pots and brewing temps...  I'll
check mine tomorrow with boiling water in the bottom container.
keep it coming
bill in wyo
On Mon, May 26, 2008 at 10:12 AM, Ben Salinas  wrote:
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13) From: Ben Salinas
My method varies some from the method Mark Prince recently posted on CG (http://coffeegeek.com/guides/siphoncoffee).I put hot water (usually just out of the tea kettle) into the bottom
chamber and place my thermometer and the top
(just resting; not engaged) into the bottom chamber.  I
put my butane burner on high, slightly off center
(the reason for this will be explained in a little bit).  Once the
water is around 92 or 94C, I take the
thermometer out, put the top chamber in all the way, and place the
thermometer in the top chamber.  At this point, while the water is rising, I
grind and weigh my coffee.  Once the water is all up, I watch the
temperature.  If it is too hot, I remove a spoonful of water and replace
it with a spoonful of cold water (or I simply stir the water
some).  If it's too cool, I usually put the lid on for a
little bit.  If that still isn't working, I'll
remove the burner for about 4-5 seconds and then
place the burner back under.  This lets a bit of water fall, heat
up some more, and then rise back up.
Once I have the water at the right temperature (around 91C usually),
I turn down my butane burner till it is just barely keeping the water in the
bottom chamber boiling.  If it gets too low, the water will fall, and if it
is too high, I get insane bubbles up top which lead to
overextraction.  The reason that I put the burner off center, is that I find
I get less bubbles up top if it is off to the side
(because the strongest boiling is not
directly underneath the tube leading to the top).
At this time I put the coffee in, start a timer, and stir quickly.  I don't
really have the stir down yet, but I am aiming to get the coffee wet without
agitating it too much.  I have found that the difference between a good pot
and a bad pot is oftentimes dependent on the stir.  If my stir takes too
long, I'll have a bitter cup.  It's especially hard in the bigger siphons.
 I had a Yama 5 Cup, and was dosing near 50g.  To stir all the coffee so
quickly is very difficult.  I just got a Hario TCA-2 and the difference is
night and day, though I am still getting used to it.
I generally let the coffee extract for about 50seconds (or maybe 1 minute).
 With the Hario, I will use a wet rag to get the coffee down as fast as
possible.  (I didn't do this with the Yama because I have been told by
people who know more than I that the Yama's will crack; Some people I have
met have had them crack on them).
My method is far from perfect, but it's an ever evolving work in progress.
It should be noted that this method was developed by Simon Hsieh of Taiwan
(a roaster there) and some friends just starting out a roastery in the
Boston area (I say this not to try to say it is better than other methods,
but because credit should be given where credit is due)
-Ben
On 5/26/08, Bill  wrote:
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14) From: Ben Salinas
<Snip>
water, but vapor pressure to achieve their brew pressure, there's something
that you may not have considered. Think about a typical vac pot with a lower
heating chamber and a tube going up to a brew chamber on top. The brew
chamber is open to the air and thus at whatever the surrounding atmospheric
pressure is. In order for the water to get pushed up to the brew chamber,
the pressure inside the heating chamber obviously has to be greater than the
surrounding atmospheric pressure, whatever that is, right?
Most definitely.  The physics of a vacpot are not too simple, but can be
conceptualized.
Assuming you don't have a lot of bubbles coming from the bottom chamber to
the top chamber (which is generally bad, in my experience), the pressure in
the bottom chamber should be approximately atmospheric pressure plus an
amount proportional to the height of the water in the top chamber (or it
might be the distance between the top of the water in the top chamber, and
the bottom of the tube; i'm not sure).
At 5000ft atmospheric pressure is approximately 12.2 psi (25 in Hg) compared
to 14.7 psi at sea level.  If I remember my physics, the pressure from the
water held up is equal to rho*g*h where rho is the density of water, g is
the acceleration due to gravity, and h is the height of the water.  Assuming
a reasonable size for h (let's say 6 inches), we get a pressure of about 0.2
psi (1440 Pascals)
So for our example of 5000 ft, the pressure inside the chamber should be
around 12.4 psi.
If these calculations are correct (I might be overlooking something very
important), then the temperature of water inside the chamber won't be that
much higher than the boiling point outside the chamber.
Pressure is interesting stuff.  It makes me wonder why we don't pull partial
vaccuums in our espresso boilers so that the water boils at the precise
temperature we want to brew at (then, by changing the pressure inside the
chamber, we could change our brewing temperature).  It would mean that our
water couldn't get hotter than our desired temperature, and it would be easy
to regulate it just be heating it.  It would probably mean that you would
need two pumps- 1 to refill the boiler, and one to draw water from the
boiler to the grouphead (as current boilers work since the boilers are
sealed- then if we push with 10 bars on the input, 10 bars will push on the
output into your grouphead).
-Ben
On 5/26/08, webviking6  wrote:
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