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premature drawdown in vacuum pot - why?
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NoahB
Senior Member


Joined: 24 Mar 2009
Posts: 28
Location: NY

Espresso: Caravel
Grinder: Asst. hand grinders
Vac Pot: Yamas
Drip: Technivorm KBTS
Roaster: Modded air popper
Posted Wed Jun 3, 2009, 1:50pm
Subject: premature drawdown in vacuum pot - why?
 

Method is as follows with 8-cup yama and cory glass rod:

Bring water in kettle just to boil.
Measure and pour water into bottom carafe and turn flame on lowest setting.
Once all water has risen I pour in the coffee grounds and give a few very gentle back and forth stirs, essentially just to get the grounds submerged.
Wait about 3 minutes and allow drawdown.

However, I have had several instances where some coffee began to siphon down into the bottom pot only moments after I added the grounds (the top globe and the glass filter were definately not disturbed or bumped). The amount of coffee (or perhaps just grounds) that gets into the bottom carafe is way more than enough to consider the pot ruined. A few more particulars:

This has happened more often than not using darker roasts (vienna). I have had successful pots using the cory, but now the failure/success ratio is about 50/50. I have never had premature draw-down using the cloth filter (which is enough for me to eliminate the possibility of a seal problem). I usually only make 12 onces at a time. (I know, I know, only full pots, but I compensate by using about 21 grams of coffee, or 4.5 tbsp). I am using my KYM hand grinder, which I admit is not a real heavyweight with grind levels outside of the espresso range. I suspect that this is on the short list of culprits, but am hoping that someone else has had issues with adding your coffee, gently submerging the grounds (no circular stirring going on here!) and looking down to notice that the water in the bottom pot is now almost black from the coffee and water that has fallen down.

I went through the list of post topics already and did not see any post subjects that pointed to a problem like this, but please accept my advance apologies as I imagine that has most likely already been covered.
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JKalpin
Senior Member
JKalpin
Joined: 28 Dec 2008
Posts: 814
Location: Thornhill, Ontario Canada
Expertise: I love coffee

Espresso: Aerobie Aeropress
Grinder: Baratza Maestro Plus
Vac Pot: Yama 5-Cup
Drip: Krups Moka Brew, BraZen
Roaster: Freshroast+8, Behmor 1600+
Posted Wed Jun 3, 2009, 7:17pm
Subject: Re: premature drawdown in vacuum pot - why?
 

NoahB Said:

Method is as follows with 8-cup yama and cory glass rod:

Bring water in kettle just to boil.
Measure and pour water into bottom carafe and turn flame on lowest setting.
Once all water has risen I pour in the coffee grounds and give a few very gentle back and forth stirs, essentially just to get the grounds submerged.
Wait about 3 minutes and allow drawdown.

However, I have had several instances where some coffee began to siphon down into the bottom pot only moments after I added the grounds (the top globe and the glass filter were definately not disturbed or bumped). The amount of coffee (or perhaps just grounds) that gets into the bottom carafe is way more than enough to consider the pot ruined. A few more particulars:

This has happened more often than not using darker roasts (vienna). I have had successful pots using the cory, but now the failure/success ratio is about 50/50. I have never had premature draw-down using the cloth filter (which is enough for me to eliminate the possibility of a seal problem). I usually only make 12 onces at a time. (I know, I know, only full pots, but I compensate by using about 21 grams of coffee, or 4.5 tbsp). I am using my KYM hand grinder, which I admit is not a real heavyweight with grind levels outside of the espresso range. I suspect that this is on the short list of culprits, but am hoping that someone else has had issues with adding your coffee, gently submerging the grounds (no circular stirring going on here!) and looking down to notice that the water in the bottom pot is now almost black from the coffee and water that has fallen down.

I went through the list of post topics already and did not see any post subjects that pointed to a problem like this, but please accept my advance apologies as I imagine that has most likely already been covered.

Posted June 3, 2009 link

What is so nice about the Vac-Pot is that you can prove that the water is at 212F because it is boiling.  If it is boiling (slowly) in the carafe and then migrates up to the top bowl it will probably be in the range of 195 to 205F, optimum for brewing.

You should be aware that it is the steam created by the half-inch of water in the carafe that keeps the water from commencing it's drawdown.  If you see steam bubbling in the upper bowl, you are in no danger of drawdown.

Once you feel the brew is complete and want to begin drawdown you remove it from the heat.  Then, steam in the carafe condenses back into water and creates a vacuum.  The brewed coffee is literally sucked down.

 
Jerry
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NoahB
Senior Member


Joined: 24 Mar 2009
Posts: 28
Location: NY

Espresso: Caravel
Grinder: Asst. hand grinders
Vac Pot: Yamas
Drip: Technivorm KBTS
Roaster: Modded air popper
Posted Wed Jun 3, 2009, 10:02pm
Subject: Re: premature drawdown in vacuum pot - why?
 

Well, I tried going through the motions this time, with just water, and am disappointed to say that the same thing happened. I brought the water to a boil in the kettle, measured out 12 oz., poured it into the carafe and put a flame under it (lowish). Once small tiny bubbles were visible inside the carafe, I put the lid on with the cory rod in place. The water rose, but once it had all just about risen, it couldnt quite get all the water to stay up. The last ounce or two (not including the 1/2 inch of water that remains under the syphon) kept shooting up into the top globe and then come right back down again. The process repeated itself. I tried raising the heat - same thing. When I tried lowering the flame to its lowest possible setting, draw-down began and completed.

Afterwards I put back in the cloth filter and proceeded to make a succesful cup. Any thought on why the rod is not working?
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BoldJava
Senior Member
BoldJava
Joined: 2 Jun 2006
Posts: 1,545
Location: St Paul, MN
Expertise: I love coffee

Espresso: '82 Oly Cremina 67
Grinder: Macap MC4 Doserless Stepped
Vac Pot: Yamas
Drip: Hario, Beehouse, Cilio, Kone...
Roaster: RK Drum and Gene
Posted Thu Jun 4, 2009, 1:01am
Subject: Re: premature drawdown in vacuum pot - why?
 

>>>I have never had premature draw-down using the cloth filter (which is enough for me to eliminate the possibility of a seal problem). I usually only make 12 onces at a time. .  . >>>

I never make partials so I don't know if that is contributing to your dilemma of premature drawdowns.  

Take a very good look at your Cory.  The raised, bumped area where it rests in the globe - do you see any missing or chipped areas that is preventing a clean seal?   What you describes suggests you are not getting a vacuum and something sounds amiss at the point of the filter where the seal would be created.

Second, hold the filter at a distance.  Does the bottom, descending portion of the rod hang straight or does it bend to one direction or another?  I have seen several that were miscast and "lean" in one direction.  If that is your case, toss it.  There is no salvaging it.

B|Java

 
"On the trail for the goats' grail..."

Dave Borton
St Paul, MN
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NoahB
Senior Member


Joined: 24 Mar 2009
Posts: 28
Location: NY

Espresso: Caravel
Grinder: Asst. hand grinders
Vac Pot: Yamas
Drip: Technivorm KBTS
Roaster: Modded air popper
Posted Thu Jun 4, 2009, 2:11am
Subject: Re: premature drawdown in vacuum pot - why?
 

No visible defects on the rod... :(
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JonR10
Senior Member
JonR10
Joined: 26 Apr 2004
Posts: 10,376
Location: Houston, Texas
Expertise: I love coffee

Espresso: E61 Legend, Livietta,...
Grinder: Robur, B-Vario-W
Vac Pot: Hario Tabletop, Yama...
Drip: Technivorm
Roaster: 1-lb US Roaster, Behmor 1600
Posted Thu Jun 4, 2009, 2:52am
Subject: Re: premature drawdown in vacuum pot - why?
 

Does it behave the same way with a full pot of water?

 
Jon Rosenthal
Houston, TX
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NoahB
Senior Member


Joined: 24 Mar 2009
Posts: 28
Location: NY

Espresso: Caravel
Grinder: Asst. hand grinders
Vac Pot: Yamas
Drip: Technivorm KBTS
Roaster: Modded air popper
Posted Thu Jun 4, 2009, 5:30am
Subject: Re: premature drawdown in vacuum pot - why?
 

Just tried a full pot (water only). All the water rose to the top. The bubbling action was a bit too tumultuous, so a lowered the flame a tad. A few moments later (about 15 seconds after all the water had risen) the ounce or two of water began its bouncing up and down the syphon a few times, and then all the water drew down into the bottom carafe, all with the flame still on!!
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JonR10
Senior Member
JonR10
Joined: 26 Apr 2004
Posts: 10,376
Location: Houston, Texas
Expertise: I love coffee

Espresso: E61 Legend, Livietta,...
Grinder: Robur, B-Vario-W
Vac Pot: Hario Tabletop, Yama...
Drip: Technivorm
Roaster: 1-lb US Roaster, Behmor 1600
Posted Thu Jun 4, 2009, 5:42am
Subject: Re: premature drawdown in vacuum pot - why?
 

NoahB Said:

A few moments later (about 15 seconds after all the water had risen) the ounce or two of water began its bouncing up and down the syphon a few times, and then all the water drew down into the bottom carafe, all with the flame still on!!

Posted June 4, 2009 link

It seems to me that the only way for this to be physically possible is that there is most likely a seal problem between the top and the bottom.  If the only airflow path into the bottom globe is through the neck of the funnel (top part) then keeping the bottom pressurized with heat will keep the water in the top.  

If the seal around the neck of the funnel leaks and allows air to escape the bottom globe, the pressure is lost and the weight of the water will draw it down.  

It seems most likely to me that the cory gasket isn't sealing properly when it gets hot.  I had a very similar problem with an antique cory vacpot. That's why I ended up getting a new Yama pot with a nice, soft, squishy rubber neck seal.

 
Jon Rosenthal
Houston, TX
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NoahB
Senior Member


Joined: 24 Mar 2009
Posts: 28
Location: NY

Espresso: Caravel
Grinder: Asst. hand grinders
Vac Pot: Yamas
Drip: Technivorm KBTS
Roaster: Modded air popper
Posted Thu Jun 4, 2009, 11:46am
Subject: Re: premature drawdown in vacuum pot - why?
 

i am using a yama, only the rod is a cory
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BoldJava
Senior Member
BoldJava
Joined: 2 Jun 2006
Posts: 1,545
Location: St Paul, MN
Expertise: I love coffee

Espresso: '82 Oly Cremina 67
Grinder: Macap MC4 Doserless Stepped
Vac Pot: Yamas
Drip: Hario, Beehouse, Cilio, Kone...
Roaster: RK Drum and Gene
Posted Thu Jun 4, 2009, 2:50pm
Subject: Re: premature drawdown in vacuum pot - why?
 

I just took a look at my 8-cup Yama.  I wonder if Jon is onto it.  The cloth filter is supplementing a faulty gasket and making the vacuum complete; the Cory rod isn't?

I give.

B|Java

 
"On the trail for the goats' grail..."

Dave Borton
St Paul, MN
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