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Usefulness of pre-heating TV carafe?  --  Test added
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Eiron
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Eiron
Joined: 12 Nov 2007
Posts: 343
Location: Loveland, Colorado
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Posted Wed Dec 19, 2007, 9:21am
Subject: Usefulness of pre-heating TV carafe?  --  Test added
 

OK, I've had my Technivorm KBTS for about 6 weeks now, & I've been thinking that pre-heating the Cater-Profi thermal carafe is an exercise in futility.  Why?  Well, this thing has to be about the best insulating container of anything I've ever owned.  I can fill it with boiling water & leave it sit for 20 min, & the exterior steel stays stone cold to the touch.  Only the plastic pour spout gets a bit warm (which is maybe why they redesigned the 10 cup carafe to eliminate the plastic?).  Even my 1 ltr stainless Thermos exterior gets warm after 5 min of pre-heating.

Admittedly, I haven't done any pre-heating temperature tests on the C-P carafe.  (I can tell you that 1/2 a carafe of coffee was only 108F after sitting for 9 hrs.)  So far I've been boiling a full liter of water & pre-heating the carafe for a minimum of 10 min whenever I make coffee.  I'm sure that heating up the interior skin provides some benefit, but if no heat is making it out to the exterior skin then I'm obviously not transferring heat to the space between the walls.  And if I'm drinking the coffee within an hour or so anyway, I'm beginning to think there's not much advantage to pre-heating.  Especially considering the extra time, energy & water waste it takes every time I want to make coffee.

So, is this ritual even necessary?  Has anyone done any C-P carafe temp tests to validate this process?  :-)

 
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svyerkgeniiy
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Joined: 14 Dec 2006
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Location: New York City, NY
Expertise: I love coffee

Espresso: (-ish) Bialetti moka pot
Grinder: Baratza Preciso
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Posted Wed Dec 19, 2007, 9:29am
Subject: Re: Usefulness of pre-heating TV carafe?
 

The benefit is that, instead of absorbing heat from your coffee and thus lowering its temperature from the initial drip, the carafe already has more internal heat from the pre-heat and thus your coffee stays hotter for longer than it otherwise would.

Having said that, I think there is some confusion out there about brewing temperature versus drinking temperature.  Brewing temperature should be between 195F-205F, but drinking temperature is significantly below that (maybe 150F-165F?).  This fact is proven when you have to let your coffee cool before you drink it.  There isn't really any need that I can see to try to keep the coffee hotter than you would drink it, except for the drop that it experiences being poured into a cold cup and from adding other non-coffee items such as dairy and sweeteners-- if you employ those.  The extra heat would also add some time to the period where it stays hot enough for you.

So, if the brew into the unheated carafe still keeps it above drinking temperature, then you really won't need to preheat.  If you want to keep it hot for longer, say for 10 or 12 hours, then a preheat would help.  Honestly I don't think brewed coffee keeps well for that long even when it isn't kept on a heat source, but perhaps you want to have a later cup without brewing a new pot at 2PM, or you have guests that you want to keep hot coffee available for.

As far as the preheat method, you are really only trying to add heat to the internal skin and not the space between the interior and exterior.  I wouldn't think you'd need 10 minutes, nor even boiling water unless you are trying to keep it really hot.  My method is to fill the carafe with hot tap water and let it sit while I prepare the rest (grounds, water, etc.).  Once the internal skin reaches equilibrium, that should be sufficient, and that happens rather quickly.  Water, and thus coffee, has a high specific heat compared to metal.  This means more energy has to be added to water than metal to raise it a given temperature differential.  This also means you get out more heat energy per degree that you do from metal, so the temperature doesn't change that much one way or the other if you're brewing a full pot.  For me, I usually brew a 3/4 pot and then pour a cup out immediately, so I don't keep that much in the carafe.

 
Donald Varona
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Eiron
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Eiron
Joined: 12 Nov 2007
Posts: 343
Location: Loveland, Colorado
Expertise: I love coffee

Espresso: Quick Mill 0930
Grinder: Quick Mill 031,...
Drip: TechniVorm KBTS
Roaster: Behmor 1600, Presto Poplite
Posted Thu Dec 20, 2007, 9:50am
Subject: Re: Usefulness of pre-heating TV carafe?
 

I agree, the first few cups from the carafe are always too hot to drink.  I also agree that it's really only the carafe's interior surface that should be getting warmed up by pre-heating.  So, since I'm off work this week, I decided to run a test.

Using a small (1" dia) frothing thermometer (like the one found here), I measured the water & air temps before brewing.  Then I measured the water temp as it fell from the filter cone into the carafe, the full carafe temp, & the carafe temp at 5 min & 10 min intervals.  I did not use any grounds in the filter basket.  I did this procedure twice.  The first round simulates what the coffee would be like if no pre-heating is done.  The second round simulates what happens when you do pre-heat.


First Round:
  • Fresh water temp:  70F
  • Internal carafe temp:  67F
  • Brewing temp:  185F
  • Initial carafe temp:  180F
  • 5 min carafe temp:  178F
  • 10 min carafe temp:  177F


Second Round:
  • Fresh water temp:  72F
  • Internal carafe temp:  140F
  • Brewing temp:  184F
  • Initial carafe temp:  182F
  • 5 min carafe temp:  180F
  • 10 min carafe temp:  179F


Bonus Reading:
  •  90 min carafe temp:  170F


I left the thermometer in the water for a full minute at each temperature reading, so the entire measuring process (after brewing) took approximately 13-14 min.  (Water finishes dripping into carafe, 1 min for temp reading, screw on lid & wait 5 min, remove lid & take 1 min temp reading, replace lid & wait another 5 min, remove lid & take final 1 min temp reading.)

Keep in mind that at these temps, a 2F difference is about a 1% change.  Can I tell at that point?  Probably not.  So I'm going to try not pre-heating my carafe for a few days.  I'll let you know if my TVBTOCD proves too strong for me to overcome.  :-)

Edit:  I should mention that I wasn't entirely correct in my earlier statement about the carafe being "stone cold" after pre-heating.  In actuality, only the lower half is cold.  The upper half does get "not cold," with the plastic pour spout getting "slightly warm."  Since I don't know how the carafe is constructed I can't tell you why.  Is it the plastic pour spout transferring heat to the metal?  Is it the top of the steel carafe (under the plastic) "wicking" heat from the inside skin?  Don't know.  And, since there's nothing I can do about it, don't care.  It's still the best insulating carafe I've ever owned.

 
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- my friend Mark, on being told of Coffee Geek's existence

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Christopher_01
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Posted Thu Dec 20, 2007, 8:47pm
Subject: Re: Usefulness of pre-heating TV carafe?
 

If it's 170 deg after 90 minutes, why bother preheating?  If you are going to drink it in 1-2 hours, and it's already hotter than you can drink it at that time, the experiment's are over.  You already answered your own question (before you even broke out the thermometer).  :^)

Best,
Christopher
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Eiron
Senior Member
Eiron
Joined: 12 Nov 2007
Posts: 343
Location: Loveland, Colorado
Expertise: I love coffee

Espresso: Quick Mill 0930
Grinder: Quick Mill 031,...
Drip: TechniVorm KBTS
Roaster: Behmor 1600, Presto Poplite
Posted Thu Dec 20, 2007, 11:50pm
Subject: Re: Usefulness of pre-heating TV carafe?
 

Hi Christopher,
Again I agree.  But the question wasn't really just my own, was it? ;-)  Most TV Thermal owners will swear by pre-heating the carafe.  Well, at least on the threads I read thru.  My goal was share the data so that others could decide for themselves whether or not this procedure is warranted.  'Cuz, as a group, us TV Thermal owners are wasting a bunch of water & energy on pre-heating!

As coffee common-sewers we often do many rituals without questioning whether or not there's any benefit to it.  Like the whole stirring-with-a-chopstick-with-the-brewbasket-closed thang.  If the silly coffee maker has been approved by both the American and European coffee brewing associations to brew "correctly" as designed/sold, then why do this??  If you want to, that's one thing.  But if you think you have to in order to get a great cup of coffee, then maybe something's wrong with either the brewer or the instructions.

Oh, & just so you have the data, the 90 min temp was taken on the 2nd filling of test brew water (i.e., pre-heated & completely full carafe).  It was a "bonus reading" 'cuz that situation would never happen at my table.  After 90 min, the most coffee I'd have left in the carafe is maybe a single cup, & I always have to warm it back up at that point.

Cheers!

Greg

 
"Just what I need - another 'geek' label..."
- my friend Mark, on being told of Coffee Geek's existence

Good, affordable espresso: www.coffeegeek.com/forums/espresso/machines/355707
Coffee's hot enough for OCD: www.coffeegeek.com/forums/coffee/machines/330079
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Christopher_01
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Posted Fri Dec 21, 2007, 3:03am
Subject: Re: Usefulness of pre-heating TV carafe?
 

Greg,

Perhaps I misunderstood, or read through your initial post too fast.  I thought you were going to do more temp experiments or further reversion to pre-heating.  I wasn't intending on implying that you shouldn't be doing the experiment in the first place.  It is nice to know that the thermal properties of the caraffe are such that you lose such a minimal amount of heat from the liquid.

I've found the same (without taking measurements) with french pressing and aeropressing straight into my Nissan mug.  There's no need to pre-heat as it's just ridulously  hot afterwards without such.

Best,
Christopher
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alsterling
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alsterling
Joined: 28 Dec 2005
Posts: 682
Location: Dana Point, CA
Expertise: I live coffee

Espresso: La Spaziale S1 (Had Expo)
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Vac Pot: Not yet...
Drip: Capresso MT-500 & Melitta...
Roaster: Hottop Digital
Posted Fri Dec 21, 2007, 12:38pm
Subject: Re: Usefulness of pre-heating TV carafe?  --  Test added
 

Eiron Said:

OK, I've had my Technivorm KBTS for about 6 weeks now, & I've been thinking that pre-heating the Cater-Profi thermal carafe is an exercise in futility..........So, is this ritual even necessary?  Has anyone done any C-P carafe temp tests to validate this process?  :-)

Posted December 19, 2007 link

Well......here's something you've mentioned that I've dealt with for years now.

While I've got a thermocouple thermometer handy, I haven't found it necessary to test and quantify pre-heating of the storing and heating ware.
We bought the Capresso TM500 for brewing of our fine ground Brasilian cafe. We drink our Brasilian cafe in demitasse cups. I have always preheated the final coffee dispensing device and the cups and saucers for serving. To extend the reply, more specifically, to the "new technology" (that could be a misnomer here...?) carafes that Technivorm and Capresso include, we preheat the carafe prior to brewing using our sink-based hot water in the kitchen. My espresso bar is in the garage and too much of a "shlep" to take the carafe on an early morning trip to the steam boiler water tap on the S1. Without preheating the carafe, it's reasonably easy to perceive a lower serving temperature of the coffee. We drink our coffee, usually, within the hour that it's brewed.

One of the challenges I've found with brewing and serving small volume Brasilian cafezinho, Turkish or Middle Eastern coffees, is the use of demitasse cups; usually thin walled porcelin. So keeping the temperature as close to the brewing temp is a goal we reach for, but obviously won't want to meet strictly.  

In general, and for all my brewing methods, I'm a firm believer that bringing any and all accessories and tools closer to the brewing temperature of the beverage is a good thing. As we all know, we don't drink at 200F, but the contact of all the items that touch the coffee from brewing to drinking is, cumulitively, one big heat sink. There's nothing less appetizing to us than drinking warm rather than hot coffee. As far as I can figure, the trick is to drink the coffee before it breaks down in its flavors and aroma.

Of course now you've got me wondering..........is this a balancing act......."I want to drink hot coffee, but heat probably breaks down the beverage." I suppose that unlike roasting, where you have to wait a few days for the beans to outgas, here the challenge is to drink the coffee as soon as you can! So while storing the coffee at higher temps is desirable; on the other hand higher temp storage probably speeds up the breakdown of the coffee!? (Maybe I should try just opening my mouth under the brewing spigot?)  :-/

Best, Al

 
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Eiron
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Eiron
Joined: 12 Nov 2007
Posts: 343
Location: Loveland, Colorado
Expertise: I love coffee

Espresso: Quick Mill 0930
Grinder: Quick Mill 031,...
Drip: TechniVorm KBTS
Roaster: Behmor 1600, Presto Poplite
Posted Fri Dec 21, 2007, 1:50pm
Subject: Re: Usefulness of pre-heating TV carafe?
 

LOL, sorry Christopher, I guess I misread your intentions as well.  Re-reading your post now, I understand your comments  completely.  No, I have no more tests planned, other than just seeing if I can re-train myself to brew w/o pre-heating.  (Shoot, this may be harder than weaning myself off 3,000 mile oil changes!)

Al, we have a Bodum "Curl" electric water kettle that I've been using to boil my pre-heating water.  It boils a full liter in just a couple of minutes, so its reasonably quick & convenient.  I'd have to run several gallons of tap water to get 125F "hot" water out of the faucet, which means that same number of gallons of 53F cold water is flowing back into my water tank & using more energy to get back up to tank temp.  Less energy & water waste with the Curl.  My mom would be so proud! :-)

Hook up that thermocouple & tell us how many degrees of cooling-off it takes until you perceive a lowered serving temp.  Are you musically inclined?  Perhaps you could write/play us all a "coffee breakdown" (on the banjo would be best, don't you think?) for our morning beverage enjoyment...  :-D

-Greg

 
"Just what I need - another 'geek' label..."
- my friend Mark, on being told of Coffee Geek's existence

Good, affordable espresso: www.coffeegeek.com/forums/espresso/machines/355707
Coffee's hot enough for OCD: www.coffeegeek.com/forums/coffee/machines/330079
Personal & global health: http://www.broomfieldenterprise.com/ci_12802509
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alsterling
Senior Member
alsterling
Joined: 28 Dec 2005
Posts: 682
Location: Dana Point, CA
Expertise: I live coffee

Espresso: La Spaziale S1 (Had Expo)
Grinder: Macap M4 & Gaggia MDF
Vac Pot: Not yet...
Drip: Capresso MT-500 & Melitta...
Roaster: Hottop Digital
Posted Fri Dec 21, 2007, 2:47pm
Subject: Re: Usefulness of pre-heating TV carafe?
 

Greg........interesting tradeoff between running the water until you get something hot versus using the electric kettle. For some reason, our kitchen sink has to run for a couple minutes or so before we get anything resembling full hot water. I've always thought that we ought to recycle the first few minutes, but my list of stuff to do is already too long. Oh well. BTW.......yes, your Mom would be proud; mine would push me aside and ask....."What are doing in my kitchen. Get outa' here!" (Love 'ya Ma)

So wanting to get "the official answer"........I called Capresso and a super nice fellow on the phones who knew less than I, and had only been with them for a short while. He gave me an 800 number to call their sales and marketing dept., but I ended up with flower shop in the state of MS??! Poor gal says she gets alot of those calls and has even called Capresso and the phone company. (I would think calling Capresso would be enough?) That ended my "go to the source" excercises for Friday, December 21st 2007.

Anyway, against all that's "he-man and masculine"...........I looked on line at the instructions for the MT500. Guess what I found when I downloaded the Adobe Acrobat file? (see their printed instruction below on the care and feeding of the carafe..............) I'm sure this would apply to your Technivorm. (While it's not an official decree...I find it conforting that my suspicions have been somewhat validated.)

Best, Al

alsterling: capresso MT500 carafe_12 21 07.jpg
(Click for larger image)

 
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CraigA
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Posted Fri Dec 21, 2007, 2:59pm
Subject: Re: Usefulness of pre-heating TV carafe?
 

alsterling Said:

Greg........interesting tradeoff between running the water until you get something hot versus using the electric kettle.

Posted December 21, 2007 link

Yes there's quite a difference in temps! Depending on where your hot water tank thermostat is set at 130, 135, 140F & a kettle right off the boil at 210 - 212F.

For some reason, our kitchen sink has to run for a couple minutes or so before we get anything resembling full hot water.

That's because you're pushing out all that cold water in that length of run of copper pipe that's just been sitting there, till the hot water exits.

 
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