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Topic: Vac-Pot Temp (15 msgs / 453 lines)
1) From: John M. Howison
IMHO, my Vac-pot with a glass rod rather than cloth brews coffee as
good as it gets.  One of my kibitzers opines that during the minute
that the water on the grounds is bubbling it exceeds 212 degrees, with
heated air and water rising under pressure.  Said kibitzer compares
the situation to that of liquid in a pressure cooker, where
temperatures exceed 212.  I disagree, because water at 212 degrees
does not produce great coffee in a French Press or an Aeropress.  I
allow for the possibility that toward the end of the "fill" very hot
water may be arriving, but does not necessarily raise the whole potful
to 212.   Scientists please comment.
-- 
Contra muros, mater rubicolla
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2) From: Doug Hoople
Hi John,
No scientist here, but I have measured the water temperatures in the vacpot
funnel, and, in my experience, you're going to have a hard time getting the
water temperature any higher than 205F under any circumstances.
My method is to take water out of a hot water kettle just off boil, pour it
into the pot (lower portion) and place the pot on a hot stove burner, let
the water rise into the funnel, and then dumping the grounds into the
funnel.  Because the rise is governed by temperature differences and not by
absolute temperatures, you can get water to rise into the funnel when it's
as cool as 155F or so.
Even taking water just off boil (just slightly less than 213F), the first
bit of water rising into the cold funnel is somewhere around 175F (!).  The
cold funnel continues to act as a heat sink, and by the time all the water
has risen to the top, I get readings around 195F.  The grounds are also
cold and will cool the water in the funnel briefly as well. The water temp
might rise another 5 degrees during the 2-minute steep time, and maxes out
around 200F or so.
I've also recommended the 'burst of heat' just before drawdown (to prevent
delays and stalls), and that burst of heat, lasting no more than about 5
seconds, doesn't raise the water temperature measureably.
You can get higher water temps by letting the water bubble at idle in the
funnel for a while before dropping in the grounds, but if you drop your
grounds in as soon as the water's at the top, your temperature curve should
be mostly as described above.  If you start with the grounds already in
your funnel, there is probably no difference in temperatures whatsoever.
I've found that coffee brewed in the 195-200F range is just about right.
 It seems that, the cooler the water, the less bitter the coffee.  Even
when the temps creep up above into the 200-205F range, it seems that the
coffee flavor takes a bitterness hit, so cooler is better IMHO.
But no, I don't think there's a problem with overheated water in a vacpot.
 .
Thanks.
Doug
On Mon, Mar 19, 2012 at 8:40 AM, John M. Howison wrote:
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3) From: John Stewart
I have the same observation on temperature.  It takes a bit more time and=
 patience to get the temperature on the vacuum pot over 190.  I usually s=
tick a thermometer in the top to track the temperature.
As to the other thread on stalling.  I use a yama pot and cory glass rod.=
  Getting the temperature on top up to 190-195 means that steam is bubbli=
ng through the top for a couple of minutes.  I'm speculating that brewing=
 to the 195ish temperature does a couple of things.  It increases the bre=
wing temperature, increases the brewing time, and it increases the agitatio=
n in the brewing chamber.  (I'm not averse to stirring the top a couple o=
f times.)  I'm thinking that the increase in brewing time and agitation m=
akes the process less likely to stall.  My speculation is that the increa=
sed time more fully expands the coffee granules and the agitation helps kee=
p the coffee from settling together.  One other note that may effect thin=
gs here is the rate and method of cooling.  I use a gas stove, and once I=
 hit the target temperature, I remove the vacuum pot from the burner and pl=
ace it on a pot holder.  My thought here is that I want the cooling proce=
ss
 to begin quickly - as opposed to leaving the vacuum pot on a hot surface.=
  I could see that leaving the brewer on a hot electric coil for instance=
, would allow the grounds to settle fully before the bottom is cool enough =
to draw the coffee down.
John
 From: Doug Hoople 
To: "A list to discuss home coffee roasting. There are rules for this list,=
 available athttp://www.sweetmarias.com/maillistinfo.html" =
Sent: Sunday, March 18, 2012 2:19 PM
Subject: Re: [Homeroast] Vac-Pot Temp
 =
Hi John,
No scientist here, but I have measured the water temperatures in the vacpot
funnel, and, in my experience, you're going to have a hard time getting the
water temperature any higher than 205F under any circumstances.
My method is to take water out of a hot water kettle just off boil, pour it
into the pot (lower portion) and place the pot on a hot stove burner, let
the water rise into the funnel, and then dumping the grounds into the
funnel.  Because the rise is governed by temperature differences and not =
by
absolute temperatures, you can get water to rise into the funnel when it's
as cool as 155F or so.
Even taking water just off boil (just slightly less than 213F), the first
bit of water rising into the cold funnel is somewhere around 175F (!).  T=
he
cold funnel continues to act as a heat sink, and by the time all the water
has risen to the top, I get readings around 195F.  The grounds are also
cold and will cool the water in the funnel briefly as well. The water temp
might rise another 5 degrees during the 2-minute steep time, and maxes out
around 200F or so.
I've also recommended the 'burst of heat' just before drawdown (to prevent
delays and stalls), and that burst of heat, lasting no more than about 5
seconds, doesn't raise the water temperature measureably.
You can get higher water temps by letting the water bubble at idle in the
funnel for a while before dropping in the grounds, but if you drop your
grounds in as soon as the water's at the top, your temperature curve should
be mostly as described above.  If you start with the grounds already in
your funnel, there is probably no difference in temperatures whatsoever.
I've found that coffee brewed in the 195-200F range is just about right.
It seems that, the cooler the water, the less bitter the coffee.  Even
when the temps creep up above into the 200-205F range, it seems that the
coffee flavor takes a bitterness hit, so cooler is better IMHO.
But no, I don't think there's a problem with overheated water in a vacpot.
.
Thanks.
Doug
On Mon, Mar 19, 2012 at 8:40 AM, John M. Howison wr=
ote:
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4) From: Seth Grandeau
I like to get the water boiling on the bottom, without the funnel in
place.  Once I get a good boil going, i dial it down to low (simmer is too
low on my stove) and add funnel with glass rod and coffee.  The water
starts rising immediately and I've measured the temp, it's always between
200 and 205.
On Mon, Mar 19, 2012 at 12:35 PM, John Stewart wrote:
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5) From: Larry Dorman
As a new yama owner who has brewed only once, what is the advantage of
a cory rod?  A response here or a link to the answer are both good
choices.  :)  Thanks!
LarryD
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6) From: j3r
On 12-03-22 03:57 PM, Larry Dorman wrote:
<Snip>
The coffee never touches anything but glass and water. The traditional 
cloth filters do have residual oils in them after cleaning, whether that 
matters or not to you is personal choice (and sensitivity of your taste 
buds perhaps).
I picked up a metal screen for the vac pot but have not tried it yet. I 
figure this may be the best tradeoff between good filtering and good taste.
Jeremy
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7) From: Doug Hoople
"I like to get the water boiling on the bottom, without the funnel... The
water starts rising immediately and I've measured the temp, it's always
between 200 and 205."
I personally think that 200-205 is on the high side, even though it's still
within the recommended 195-205 range.   For one thing, it's invites
inadvertantly slipping higher than 205, which brings on bitter notes. For
another, I think the cooler end of the favored range yields a generally
sweeter, less edgy cup.
That's actually a good reason to boil separately in a kettle and pour the
water just off boil into a room temp pot.  That small amount of extra
cooling brings the temperature to just the right level.  The general range
in the funnel from the end of the rise to the beginning of drawdown will be
between 195-200.
YMMV, though. And if you like the brew you're getting, don't change your
procedure.
Doug
On Fri, Mar 23, 2012 at 1:32 AM, Seth Grandeau  wrote:
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8) From: Doug Hoople
Hi Larry,
I'm assuming that you're asking about the glass rod vs. the cloth filter,
and not about the Cory rod vs. the Cona rod.
With the cloth filter, flavor elements of both the cloth and of residues
from prior pots make their way into the cup.  Some people don't detect
this, but others (myself included) find the taint to be quite pronounced.
With the glass rod, the coffee comes into contact with nothing but glass,
and the resulting cup is as pure as you could possibly hope for.
The glass rod is also a lot easier to clean vs. the cloth filter.
If the question was Cory vs. Cona, the Cory is a bit heavier, and the extra
mass seems better suited to brewing in the Yama.
The disadvantage of the glass rod, of course, is that it's prone to delays
and stalls during drawdown.  Totally manageable with a simple modification
in the brewing procedure, so no big deal.  But there is a small level of
skill required in using the glass rod.
The cloth filter is utterly flawless in that regard, and can be
successfully used on day one by a complete newbie.
Doug
On Fri, Mar 23, 2012 at 8:57 AM, Larry Dorman  wrote:
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9) From: Larry Dorman
This seems like a really good idea...  where do you get the metal
screen?  I would expect this is something that could be thoroughly
cleaned between uses, minimize any sediment, and avoid most stalling
situations...
LarryD
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10) From: Larry Dorman
Thank you, Doug...  very thorough answer to both the question I asked
and the one I didn't know to ask.  :)
I can certainly see where the cloth filter would offer some taint over
time.  The instructions told me to store it in a tub of water in the
refrigerator between uses.  Is this what others do?  It looks like I
got a second filter with mine... how long do people usually go before
changes?
LarryD
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11) From: Seth Grandeau
For me, the big advantage of the glass rod is cleanup.  I'd love to say
it's that I taste a "cleaner cup" knowing that my coffee has never touched
anything other than glass, but it wouldn't be true.  I brewed with the
cloth when I first got the vac pot and I personally (YMMV) did not notice a
difference, when I switched to the cory rod.  I did notice that my cleanup
went to almost nothing, as the glass rod is very easy to clean up, compared
to reusing the cloth filter.
Regarding the sediment issue, I agree that it is much less than a french
press.  I always move the brewed coffee to a thermal carafe, after
brewing.  Give the coffee a few seconds to settle, then pour into the
carafe.  When I see the tiny trail of sediment making a run for the
thermal, I stop pouring.  What ever little bit may make it into my thermal
carafe settles out and never seems to get into the cup.  In fact, I usually
get a "cleaner" cup than my drip coffee maker with gold filter does, as a
some always seems to run over the top and into the carafe.
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12) From: John Borella
You can buy the stainless screen from Northwest Glass for around $6 & it
fits right into the Yama/Hario paper filter holder. I got one in recently &
tried it for 3 days before switching back to my cloth filters. The screen
does improve drawdown times but it also lets sediment/fines pass through
into the lower globe. This gave the brew a bitterness that I never get with
the cloth filters. I played with different grind settings but wasn't
interested in wasting a lot of time & coffee over the screen. With the
cloth filters I get a sweet, clean pot every time & I don't mind cleaning
them as I keep 4 in use so I only have to give them an Oxyclean Free bath
every 4 days. Once clean I store mine dry & have had no issues with smell
or taste in over 3 years of using this method.
John B.
On Fri, Mar 23, 2012 at 11:48 AM, Larry Dorman  wrote:
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13) From: sci
I even use my Cory glass rod in the Bodum Santos (as well as my larger
Cory). Works fine. And, I use the Bodum disk filter (a hard plastic disk
with special grooves, without any cloth) in my table top Hario. It works
fine too. I never have to worry cleaning a cloth filter. What's not to
like? Maybe a touch of sediment. But like others here, I pour the coffee
into an insulated carafe and stop pouring the last 1/2 ounce where the
sediment is. As for temps, I have done temp probe checks throughout the
brew process and here's how I get best results: add hot water in the base,
add the siphon top and let water go up, bring to a slow boil, let it sit
and preheat the whole unit, add coffee, stir, set timer. I usually get
temps around 202F (I'm at 350ft above sea level), but some of the bubbles
coming up and around the seal can get upwards to 208f. Still, the taste is
what counts and it isn't bitter. I initially had a problem with very low
temps in the upper. The water will go up even at 150f, far too cold.
Another tip to the wise: be very careful with flash boil and superheated
water.
Here's my short tale: I preheated water for my Hario T5, poured it in the
perfectly clean base to preheat, dumped that, added full amount of hot
water (20 oz.). I put it over a butane micro burner, and waited . . . and
waited. No boil?? I'm hovering over the top (what an ignoramus), looking
down the neck, nothing. It took far too long to reach boil with the burner
turned up high. I walked to the other side of the kitchen to get my ground
coffee out of my Virtuoso. Then BOOM!!!! A volcanic like explosion of
violent proportions, nay epic proportions, blasted out of the little base
all the way to the ceiling. It all happened in 1/4 of a second; I saw it
all. There was less than half of the water left in the base. What happened?
Superheated water. I've been told that there were no nucleation sites for
the bubbles to form, so ALL of the water reached 212f at the same time.
Every molecule crossed the threshold simultaneously. I still shudder to
think what I would be like today if I had remained hovering (stupidly of
course)  over the top, blinded no doubt. Well . . . there was never a
warning anywhere about this. Now I know that you are supposed to put the
top chamber on and bubbles will form allowing a normal boil.
FWIW,
Ivan
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14) From: Seth Grandeau
Super heating means that you got the water well above 212, because without
nucleation sites, you don't get the boiling process, which holds the temp
at 212.  Then, when you get one bubble, it's spontaneously sets off the
others, releasing all that energy at once.  I've done it with the
microwave, but I've never heard of it happening on a burner.  I'm glad you
didn't get hurt.
On Tue, Mar 27, 2012 at 9:53 PM, sci  wrote:
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15) From: Doug Hoople
+1 for relieved that you weren't hurt.  That was a close call.
Interesting stuff, though.  Everyday life is teeming with dangers, isn't
it?
Doug
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