[Homeroast] Vac-Pot Temp

Doug Hoople doughoople at gmail.com
Sun Mar 18 16:19:54 CDT 2012

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.


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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