HomeRoast Digest


Topic: moka pot, elevation (30 msgs / 809 lines)
1) From: David Martin
I bought a 10-tasse moka pot a few weeks ago. Purely as a piece of
equipment, I really like it - it has a certain 'metallic' aesthetic -
but up until now I've had trouble getting it to brew a good cup. When
I use it in the recommended way the coffee comes out lacking flavor.
However, after following some of the techniques from the recent MP
discussion, I think I've finally had some success. I just brewed up
some Yemen Mokha Mattari, which came out quite good. Here's what I
did:
  0. Used a fine grind, just a little bit courser than what I do for AP
  1. Pre-boiled the water.
  2. Held the MP partly off the electric burner, moving it closer and
farther to ensure a small but steady flow
  3. Took it off the heat before it finished, yielding a concentrated
brew which I then diluted with hot water
The result was good enough to ensure my MP does not find its way to
the back of the cupboard with  the other forsaken appliances.
I'm curious about one thing - if I understand the principle correctly,
the key is to minimize the rate of flow, thus preventing the water
temperature from going too high. If so, could it be the case that the
moka pot is best used at higher elevations, where the boiling point is
lower? I'm pretty close to sea level. If I were at 6000 ft, maybe it
wouldn't require as much manual intervention. Opinions?
-Dave
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2) From: Bill
Dave,
I haven't experimented enough with flow rate.  I'm the type that once I find
a way to make it good, I don't mess around to make it amazing...
Yes, you're asking the question that I've wondered.
What's the principle of the moka pot, boiling point or atmospheric pressure?
I suspect that it's pressure.  That's the case with the vac pot, which means
that in Cheyenne (6000 ft), the water goes north around 190F.  And I believe
that at sea level, the pressure in the vac pot equalizes right about 200F...
I think that the Moka Pot operates by the same principle, that the water
begins to travel through the grounds and into the reservoir, once the
pressure in the water tank equalizes with atmospheric pressure.
Man, I would love it if someone who actually knows some science would jump
in here and tell me if I'm close or totally off-base!
Great question Dave
bill
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3) From: Bill
I've googled the question of how a moka pot functions, without a decent
find... lots of the basics, but nothing beyond that.  Anybody got a good
site that explains the way a moka pot works??
bill
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4) From: Ira
At 03:24 PM 10/5/2008, you wrote:
<Snip>
When you heat water it turns to steam and that steam pushes the water 
up the tube through the coffee and out the top. I usually start with 
cold water and put it on a very low flame. I don't know if it's 
boiling in the bottom when it starts going up, but it seems to be 
boiling at the end. I'd guess that in order to get much pressure it 
would have to be at the boiling point. Some with an espresso machine 
with both pressure and temperature might give us an idea of what 
happens.  I have my Brewtus set at 96 and there is just enough 
pressure to get water to come out of the group without the pump 
turning on, I doubt it's enough to brew a moka pot.  Something you 
might try is putting a glass marble, stainless ball, penny or 
something similar in the bottom. It creates a place for the boiling 
to start so you might get more control or find the brew temperature 
is slightly decreased.
Ira
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5) From: raymanowen
I'm an absolute MP freshman wannabe. There is hope. In the right hands, it
will prove to be an astounding brew.
I think your 10-T might fill with 16 oz of hot water to the relief valve in
the lower tank. At a nominal coffee : water ratio of 1.5g : 1oz to as much
as 2.0 : 1, the brew is totally sensitive to the grind size and the actual
brewing time. 24g - 32 g of grounds
More than that, I know nothing. My next brew in the 6-T Bialetti (10 oz H2O)
will be 21g of Brazil Cerrado S-D Moreninha Formosa, ground at 1.0mm burr
separation, 2:30 time.
The brew timer starts when the floor of the upper tank gets hot with the
rising brew. Let's see what happens this time...
Cheers, Mabuhay and Magandang Gabi -RayO, aka Opa!
Got Grinder?
On Sun, Oct 5, 2008 at 2:23 PM, David Martin  wrote:
<Snip>
-- 
"When the theme hits the bass, I dance the Jig!" - -Virgil Fox at the Mighty
Wichita (ex- NYC Paramount) WurliTzer- 1976
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6) From: David Martin
On Sun, Oct 5, 2008 at 7:13 PM, Ira  wrote:
<Snip>
Now I'm curious. My hunch is that it's possible to achieve enough
steam pressure without reaching the full boiling point, but I don't
know for sure. Some time this week I'm going to see if I can figure
out a way to get a thermocouple probe into the grounds as they brew.
Not sure if this is possible without damaging the MP, but if it is, I
should be able to tell whether moderating the heat actually affects
the extraction temperature.
-Dave
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7) From: Bill
Ira, of course!  You hit it on the head.  The important thing to note on the
MP is that the water is forced up a stem by pressure.  If there was no stem,
if the water just boiled into the upper container, it would be 212 at sea
level.  But it isn't.  The water vapor pushes the water up the stem, and
that is dependent on atmospheric pressure equalization, not boiling point.
I was googling and actually ran across a post that I made regarding vac pots
back in May and it had the link I was looking for:http://twoloonscoffee.com/map/boiling_point.php They claim in section 2
that the atmospheric equalization point of water at sea level is 200F, and
at 5000 ft it's 191F...
So that explains why you lowlanders need to keep your MPs to a seep and make
sure you pull well before you get a full-blown 212 steam jet scalding
through your grounds....
But RayO, doesn't that mean that we want to have boiling water (or near)
pushing through the grounds?  I'm 1000 ft higher than you, but still...
I was searching the archives in regard to this issue, and I saw Pecan Jim
say that the MP should only be used at 7000 ft or higher...  I wonder if
that's what he was getting at...
I love this list, roasting, and drinking delicious coffee.
bill
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8) From: raymanowen
"Now I'm curious.
My hunch is that it's possible to achieve enough steam pressure without
reaching the full boiling point, but I don't know for sure." [Vapor
Pressure- it's minor below the boiling point (bp)]
[Below the bp no steam pressure is generated. In the liquid phase, (0° C -
100° C) water has a temperature-dependent vapor pressure. 100° C is the
normal sea level temperature at which the vapor pressure has risen to the
atmospheric or barometric pressure.] The temperature stops rising at the
boiling point.
The steam temperature doesn't rise above the bp until all of the water has
been vaporized. It takes a lot of heat and just makes steam. Steam is a gas
like air, and can also be heated. Otherwise, it's the temperature of the
water that vaporized, =bp.
"Some time this week I'm going to see if I can figure out a way to get a
thermocouple probe into the grounds as they brew."
[The grounds receive heat from the boiling water forced up from the bottom
reservoir.]  It's not magic- the heat source gives up energy to the water at
the bp. As the water heats everything it touches, it loses energy and the
water temperature drops below bp.
If a container of water feels hot to you, it is losing thermal energy to the
air or your finger tips. If it were not losing energy and cooling off, it
wouldn't feel hot either.
Midway through the brew cycle, I measured 186° - 187° F in the Technivo=
rm
basket.
Cheers, Mabuhay, Magandang Gabi -RayO, aka Opa!
On Sun, Oct 5, 2008 at 9:11 PM, David Martin  wrote:
<Snip>
od
<Snip>
at
<Snip>
me
<Snip>
us
<Snip>
m.
<Snip>
or
<Snip>
ee.com
<Snip>
-- =
"When the theme hits the bass, I dance the Jig!" - -Virgil Fox at the Mighty
Wichita (ex- NYC Paramount) WurliTzer- 1976
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9) From: Bill
A little light reading before bedtime RayO.  I suspect you might understand
it better than I!
But if I read it correctly, doesn't it say that atmospheric pressure is
equalized before 100C?
I would really love to understand this... not sure that I will...
bill
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10) From: David Martin
On Sun, Oct 5, 2008 at 8:56 PM, Bill  wrote:
...
<Snip>
I wonder if there's a correlation between people who like moka pots,
and high elevation.
-Dave
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11) From: raymanowen
OK - But the MP is going to speak in a few hours.
Hmmm- just thought of something. It would be inconvenient, but the top of
the MP could have a soft gasket installed on the top rim, to seal a glass
cover. Plumb in a vacuum line to the Sharper Image Bean Vac.
Sarah got me one before they went to blazes. She's managing a Lane Bryant
now- about where her Uncle Bill used to take off from Stapleton Airplane
Patch.
That would have the opposite effect of a pressure cooker, and cause the
water to boil and make steam at a lower temperature. You could monitor the
actual water temperature in the lower tank with a short metal-sheathed
thermocouple.
Just remove the safety relief valve and install a compression fitting to
match the thermocouple sheath diameter (S/S or Inconel, with a grounded
junction, a couple of feet of s/s braid lead wire and a miniature male
connector, type K to match the digital meter compentation.)
Then all you have to do is monitor the progress of the forced brew through
the glass top and watch the temperature of the water in the lower tank. The
brew temperature will drop as you force the water to vaporize (boil). You
wouldn't care about the actual vacuum level, only the brew rate and
temperature.
Maybe a little counter intuitive, but prototype operation (hot modding) is
inconvenient, as advertised.
Cheers, Mabuhay and Magandang Umaga -RayO, aka Opa!
On Sun, Oct 5, 2008 at 11:54 PM, Bill  wrote:
<Snip>
-- 
"When the theme hits the bass, I dance the Jig!" - -Virgil Fox at the Mighty
Wichita (ex- NYC Paramount) WurliTzer- 1976
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12) From: raymanowen
"...meter compensation." Duh
On Mon, Oct 6, 2008 at 1:29 AM,  wrote:
<Snip>
-- 
"When the theme hits the bass, I dance the Jig!" - -Virgil Fox at the Mighty
Wichita (ex- NYC Paramount) WurliTzer- 1976
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13) From: kevin creason
<Snip>
No, I don't think so anyway... I'm about ten or twelve over sea level and I
like MP. I like it mostly when I'm camping though since I have a Cory VP
(that is more fun to watch) and an espresso machine for home.
-- 
-Kevin
/* Never argue with an idiot. They drag you down to their level and beat you
with experience. */
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14) From: Rich
RayO;
Casting real thermodynamics in front of imitation ... .  A loosing =
proposition, I think.
raymanowen wrote:
<Snip>
<Snip>
C -
<Snip>
he
<Snip>
<Snip>
as
<Snip>
<Snip>
 at
<Snip>
<Snip>
the
<Snip>
<Snip>
vorm
<Snip>
<Snip>
<Snip>
te:
<Snip>
<Snip>
od
<Snip>
at
<Snip>
me
<Snip>
us
<Snip>
m.
<Snip>
or
<Snip>
fee.com
<Snip>
<Snip>
<Snip>
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15) From: Brian Kamnetz
Same here, I use a moka pot daily, and am barely above sea level,
couple hundred feet at the most is my guess. But I am very careful to
keep the seep as slow as possible, though findings seem to be
indeterminate. Kris addressed this a while back:
Let me know if your brew changes.  When I first got a moka pot, I looked up
a number of how-tos (including Tom's, discussion on this list, and
Stumptown's) and was doing all sorts of tricksy maneuvers right out of the
box - preheating, stopping early, letting the flow stop and start, etc.- but
the brew was always a little bitter.  However, whenever my husband was in
charge of the pot, it came out great, no bitterness at all.  I assumed he
was following all my complex directives until one morning I just asked him
how he was doing it.  He said, "Well, I put it on low heat and take it off
when it sputters". :-)  Darn it!
Brian
On Mon, Oct 6, 2008 at 7:55 AM, kevin creason  wrote:
<Snip>
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16) From: David Martin
<Snip>
Enlightenment! Epiphany!
This reduces it to just two variables - the grinder setting and the
burner setting.
I will try this. :-)
-Dave
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17) From: Rich
One of the reasons for the very slow heating is to heat the bulk of the 
water to the boiling point.  Hot watter rises to the top and is replaced 
with cold water which heats and rises. this cycle continues until the 
bottom water in contact with the heat source reaches boiling and 
internal pressure starts to rise forcing water up through the ground 
coffee.  The temperature of the boiling point is determined by the 
internal pressure switch is a combination of the barometric pressure and 
the additional resistance of the ground coffee.
Brian Kamnetz wrote:
<Snip>
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18) From: Cameron Forde
I think that one of the reasons not to tamp the MP is so that the
"puck" introduces little pressure gain.  The pressure gain comes
entirely from the height of the column of water (rho.g.h).  This
corresponds to about 5 milli-atmospheres over atmospheric for a column
of 5 cm.  This shouldn't have much affect on the boiling point.
Cameron
On Mon, Oct 6, 2008 at 1:42 PM, Rich  wrote:
<Snip>
-- 
ceforde
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19) From: David Martin
A quick followup: I've brewed a couple of pots this way - not
bothering to pre-heat the water, leaving it on very low heat and
basically ignoring it until it's done - and I'm pleased with the
results. For what it's worth, I stuck a thermocouple probe in the
coffee as it exited the spout and it read 198F, which I guess is
ideal, even if it's a couple of degrees hotter in the grounds. Now I'm
curious to see what temperature it would be if I put the burner on
'high'...
On Mon, Oct 6, 2008 at 9:42 AM, David Martin  wrote:
<Snip>
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20) From: raymanowen
"...I'm curious to see what temperature it would be if I put the burner on
'high'..."
You'll have to watch it like a hawk- when the brew actually starts, it'll go
like Mt. Vesuvius! The temperature will rise a little. Wonder what that will
do to the flavor?
I'm just finishing up a 6-T Moka pot "Americano" from 24g of the Brazil
CS-DM Formosa, 26 hrs since FC+ roast.
Grind = 44 (0.0267"), brew time = 1m:57s.
It would have brewed much faster if I hadn't modulated the heat. (After the
preheated water started boiling rising, brewing and rising in the upper
stem, I held the pot in the heat plume above the surface element.) If I
hadn't done that, it would have gone too fast
Hint: You could even start out with a lower tank full of ice cubes. What
will the water temperature be when it starts boiling and the water starts to
rise up the funnel stem?
Added 2 oz hot water to brew, and this has lasted hours in the Nissan
Stainless travel mug with some steam from the Carpeso Leaks. Unequaled
flavor, toasted Hazelnuts, Smoooth.
Tuesday morning's cup, I guess. Nice, relaxing cup. Last sip and lights out.
Cheers, Mabuhay and Magandang Umaga -RayO, aka Opa!
On Tue, Oct 7, 2008 at 11:46 PM, David Martin wrote:
<Snip>
-- 
"When the theme hits the bass, I dance the Jig!" - -Virgil Fox at the Mighty
Wichita (ex- NYC Paramount) WurliTzer- 1976
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21) From: David Martin
On Wed, Oct 8, 2008 at 12:50 AM,   wrote:
<Snip>
Based on experience I think it will kill the flavor. I used a hot
burner (not full heat, but a fairly high setting) on my first attempts
with the MP, and I suspect this is the reason they ended up tasting
like Maxwell House.
<Snip>
I'm having good luck with just using cold water, sticking it on the
burner at a low setting, and just forgetting about it until I notice
that it's brewing. I seem to be getting a nice gradual flow this way
without any intervention.
-Dave
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22) From: Brian Kamnetz
On Wed, Oct 8, 2008 at 12:25 PM, David Martin  wrote:
<Snip>
I heat the water in the microwave nearly to boiling first, but only to
speed up the process, not because I think it produces better coffee. I
use a Bialetti "Class" Stainless Steel moka pot, which because of the
way it is rounded is hard to heat on my gas burners.
Tom's current offering, the Bialetti Musa, is broader and flatter on
the bottom and therefore probably heats a bit more handily on gas
burners. So I like the shape of the Musa more, but I like the mirror
finish on the Class. Can't have everything, I guess....
Brian
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23) From: Angelo
I'm wondering if anyone has tried this item, or something similar?http://snipurl.com/46w42    I wouldn't pay to much attention to the 
description.
I have one that I picked up in a thrift shop, but I don't own a 
microwave. I was just curious about the quality of the brew. It seems 
like it should work because all the water would heat to the same temp 
at the same time, thereby insuring that the first of the rising water 
would not be cooler than the later water, which is what  happens in a 
metal moka pot, as well as in a vacuum brewer.. As a matter of fact, 
the bowl that holds the coffee basket is lined with a metallized 
plastic which, I would imagine, heats the water even more as it 
enters the chamber...
I guess I'll have to bring it w/me when I visit someone with a 
microwave...  :-)
Ciao,
Angelo
<Snip>
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24) From: raymanowen
"It seems like it should work because all the water would heat to the same
temp at the same time...insuring that the first of the rising water would
not be cooler than the later water, which is what  happens in a metal moka
pot,"
[Herein lies a little project- stay tuned.] -ro
On Wed, Oct 8, 2008 at 3:57 PM, Angelo  wrote:
<Snip>
-- 
"When the theme hits the bass, I dance the Jig!" - -Virgil Fox at the Mighty
Wichita (ex- NYC Paramount) WurliTzer- 1976
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25) From: raymanowen
The "little project."
Starting with hot water from Technivorm carafe.
Set directly on heat. Did not modulate heat to extend brewing time since I'm
not really brewing
T=0:00   80° F At top of upper stem
    0:05   85° F
    1:10  102° F
    1:25  201° F  ?? Just steam vapor, no liquid . Forgot the lower funne=
l !
!
Restart- with complete  assembly!
T=0:05   140° F  Hot start again - Not brewing yet. Set directly on med=
ium
electric heat...
    1:00   200° F Suddenly started brewing, no heat modulation.
    1:15   201° F Upper tank 1/2 full of hot H2O. Measured H2O temp = 1=
87° F
    2:15   201° F Completed, no more H2O rising, just blowing steam vapor.
This is just an anecdotal test result.
For a real test, at least 5 runs required, with lowest and highest results
discarded. Average the data from the remaining three runs.
Who cares? It's just numbers.
This test was not definitive, just showed the trend.
Cheers, Mabuhay and Magandang Gabi -RayO, aka Opa!
Hope this doesn't doom the flavor in my cup...
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26) From: james McDougal
I was just rereading this interesting series of posts and think maybe
we were emphasizing the wrong concepts.
Isn't it possible that all the discussion about the pressure at various
altitudes and temperatures is not so applicable to a MP as it is to a
percolator.
Could it be that the coffee puck provides back pressure and the water will
not move up through the coffee until that pressure is overcome. Here's my
argument: It is possible to pack the coffee too tightly for the MP to brew
(voice of experience) and there is a pressure relief valve in the bottom of
the MP. Therefore both of these suggest that the pressure provided by the
coffee puck has to be overcome by the thermal energy applied to the bottom
of the MP before the seeping starts.
This suggests that a MP packed with coffee the same way would brew the same
at altitude as sea level. It's a high pressure system.
Am I way off base here?
Jim
On Wed, Oct 8, 2008 at 11:04 PM,  wrote:
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27) From: raymanowen
"...a MP packed with coffee the same way would brew the same at altitude as
sea level. It's a high pressure system"
? ?
The INSTRUZZIONI D' USO say that il filtro should be filled with coffee
grounds without pressing it.
The filtro on mine is about 61mm diameter. I might be tempted if I had a
58mm tamper, but it would still violate the INSTRUZZIONI D' USO. "non
lasciare, oder ohne dabei diesen fest zu drücken."
If you do pack the coffee, it evidently will brew the same at s/l as in the
mountains- bad.
Die GEBRAUCHSANWEISUNG so versprechen.
If the coffee were packed to the point of restriction of the rising water, 1
bar gauge pressure in the lower tank would disperse coffee grounds out from
the filter with 67 pounds of pressure. Pressure can not even exist in the
pot unless there is a restriction to flow.
The Mocha pot is similar to the espresso maker in two respects: coffee and
water. Pack the coffee grounds in one, not the other. The one uses pressure
extraction, not the other.
The machine that fills the filter with ground coffee is the likely culprit
if you're getting croppy caffee.
Cheers, Mabuhay, Magandang Gabi -RayO, aka Opa!
Got Grinder?
On Wed, Oct 15, 2008 at 2:00 PM, james McDougal wro=
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"When the theme hits the bass, I dance the Jig!" - -Virgil Fox at the Mighty
Wichita (ex- NYC Paramount) WurliTzer- 1976
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28) From: james McDougal
Hey Rayo,
Think there is any chance that a full untamped (but tapped on a counter)
filter would provide backpressure when the coffee swells with water and the
vapor pressure in the bottom half presses it against the bottom of the top?
Visual inspection of a filter prepared according to instructions suggests
that it has been pressed tightly against the top.
Jim
On Thu, Oct 16, 2008 at 1:26 AM,  wrote:
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29) From: raymanowen
"...any chance that a full untamped (but tapped on a counter) filter would
provide backpressure when the coffee swells"
At first, I thought "Yeah, sure, it could do that if you stacked that much
coffee in it before you put the top filter plate on it and screw it
together..." Then I realized that the actual words in the directions say to
do just that.
"Fill with cold water the little tank without exceeding the hole of the
safety valve..." [Check]
"Fill the filter with ground coffee without pressing it and remove the
coffee powder from the rim of the little tank." [Oops!]
Nothing to say about the actual brew, between "Put the coffee pot on the
heat source," and "When the upper part is full of coffee, take it off the
heat..."
RTFM will be my next procedure. Thanks for the clue, Jim.
Cheers, Mabuhay and Salamat Po -RayO, aka Opa!
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30) From: raymanowen
Update:
The filter holds 30g+ of beans.That was very intense straight, but Karen,
the Celtic Critic, loved the resulting Americano when I added 40% water by
vol. I just brewed 20g straight: Panama Carmen Estate 1800m, C+, roasted
8hrs ago.
2 batches in the FR, 432° F, 16:05 end-to-end. Previous roast of this PCE
1800m was more like FC+. An entirely different flavor experience- sure glad
I got the Fiver.
Cheers, Mabuhay, Magandang Umaga -RayO, aka Opa!
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