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Netphilosopher
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Posted Thu Apr 19, 2012, 7:44am
Subject: Re: coffee refractometer
 

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gt
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Posted Thu Apr 19, 2012, 9:27am
Subject: Re: coffee refractometer
 

I would say:

((.0193x215.4) / 23.9) x 100 = 17.4%
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Netphilosopher
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Posted Thu Apr 19, 2012, 11:58am
Subject: Re: coffee refractometer
 

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gt
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Joined: 29 Jan 2007
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Location: Mpls/St Paul MN
Expertise: I like coffee

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Grinder: Virtuoso
Drip: Cones & CCD
Roaster: P1 w/ variacs
Posted Thu Apr 19, 2012, 12:27pm
Subject: Re: coffee refractometer
 

So did you press a little harder on the first cup?

Maybe try pressing 3/4 into one cup then the last 1/4 into a second cup and see how the strengths compare.
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Netphilosopher
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Posted Thu Apr 19, 2012, 1:34pm
Subject: Re: coffee refractometer
 

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Netphilosopher
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Posted Thu Apr 19, 2012, 1:37pm
Subject: Re: coffee refractometer
 

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jpender
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jpender
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Posted Thu Apr 19, 2012, 6:05pm
Subject: Re: coffee refractometer
 

I recently did an immersion brew at 21% brew ratio. Just under half the water was retained in the grounds. The standard way of calculating extraction is just solids in the cup divided by initial coffee and this resulted in a value of 12.3%. This was a hot brew that was left on the grounds for many hours and it sure didn't taste underextracted.

But suppose all of the liquid in the grounds was included in the calculation?
Then the extraction would be given by:

adjusted extraction = (s/c)*(mc + mf + (1/(1-s))*(mp + s*(mc+mp) - c)

where

s = strength
c = initial coffee mass
mc = mass in cup
mf = mass in filter
mp = mass of puck

In the case of my brew the adjusted extraction is 23.5%.

For Netphilosopher's brews, the adjusted extractions are 20.7% and 20.6%, respectively.

For an apples to apples comparison with other brews it probably makes sense to pretend that some "typical" fraction of the liquid in the puck is not part of the extracted solids.
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Netphilosopher
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Posted Fri Apr 20, 2012, 4:45am
Subject: Re: coffee refractometer
 

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jpender
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jpender
Joined: 11 Jul 2011
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Location: California
Expertise: I like coffee

Grinder: OE LIDO
Vac Pot: S/S Moka Pot
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Posted Fri Apr 20, 2012, 9:51am
Subject: Re: coffee refractometer
 

Netphilosopher Said:

The calculated extraction was 18.3%, but using the brew mass technique, it's more like 21%.

Posted April 20, 2012 link

I don't know if you remember in the old Aeropress thread where Alan Adler was doing what we're talking about. AndyS reprimanded him for using a non-standard extraction value in order to fluff up his results. I always thought that was an interesting exchange. We use the idea of extraction in two ways.

If you brew perfect coffee but spill half of it does the extraction go down by 50%?

In one sense it does, but the balance of extracted components doesn't change. The problem is that we use extraction as a proxy for this balance since we have no other simple means for measuring it (other than our senses). So the two ideas, one about economics and the other about balance, are conflated.
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Netphilosopher
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Posted Fri Apr 20, 2012, 1:21pm
Subject: Re: coffee refractometer
 

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