[Homeroast] Vac-Pot Temp
johns_webmail at yahoo.com
Mon Mar 19 11:35:08 CDT 2012
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 stick 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 bubbling 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 brewing temperature, increases the brewing time, and it increases the agitation in the brewing chamber. (I'm not averse to stirring the top a couple of times.) I'm thinking that the increase in brewing time and agitation makes the process less likely to stall. My speculation is that the increased time more fully expands the coffee granules and the agitation helps keep the coffee from settling together. One other note that may effect things 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 place it on a pot holder. My thought here is that I want the cooling process
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.
From: Doug Hoople <doughoople at gmail.com>
To: "A list to discuss home coffee roasting. There are rules for this list, available at http://www.sweetmarias.com/maillistinfo.html" <homeroast at lists.sweetmariascoffee.com>
Sent: Sunday, March 18, 2012 2:19 PM
Subject: Re: [Homeroast] Vac-Pot Temp
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.
On Mon, Mar 19, 2012 at 8:40 AM, John M. Howison <johnmhowison at gmail.com>wrote:
> 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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