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Discussions > Coffee > Machines > Coffee ratios  
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rasqual
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rasqual
Joined: 29 Jun 2005
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Posted Mon Mar 3, 2014, 8:00pm
Subject: Re: Coffee ratios
 

LOL

This thread quickly validated the domain name of the forum. Plaudits all around!

Far be it from me to abstain:

andys Said:

I, too, am a fan of the metric system. but it doesn't supersede the intrinsic properties of matter.

Posted March 3, 2014 link

Depends on whether one is concerned with extraction at the molecular level, where quantum reality might conceivably intrude on Newtonian conveniences. Collapsing the wave function while measuring . . . well . . .

Schrödinger's ristretto?

You can either time the shot or PID the temps -- but not both.

But that'd be dialing the grind in a wee bit too fine, I think.

;-)

Meanwhile, I'm working on my latest Aeropress hack.
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andys
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andys
Joined: 10 May 2003
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Posted Mon Mar 3, 2014, 9:39pm
Subject: Re: Coffee ratios
 

rasqual Said:

This thread quickly validated the domain name of the forum. Plaudits all around!

Posted March 3, 2014 link

Hi Scott:

I happily accept what (I think) is praise for a topic well-geeked.  ;-)

BTW, Vince Fedele told me that the 4% difference in water density from room temp to boiling was apparently not recognized by extraction yield pioneer Earl Lockhart of the Coffee Brewing Institute in the 1950's and 60's. Vince said that Lockhart's error was the main reason why the CBI's 20% extraction yield target became 19% when Vince first published his Extractmojo software.

Oh, and good luck with your nanofiltration project. Goodbye polyester filters!  :-)

 
-AndyS
picture page:  http://flickr.com/photos/andy_s/sets/
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MWJB
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Posted Tue Mar 4, 2014, 4:27am
Subject: Re: Coffee ratios
 

boar_d_laze Said:

Quit busting my balls and -- after remembering that the context of this thread is COLD brewing -- either don't measure your water as it approaches boiling or account for the difference if you labor under the mistaken belief that it matters.  

My points are as follows:
"Gram" is a unit of mass as well as weight (mass at the sea-level, surface of the Earth).  The context for "surface of the Earth," was to differentiate ordinary brewing from -- say -- brewing on the "surface of Jupiter;"
The inherent lack of precision in food preparation is the reason I kept my numerical expressions to one (count it, "1") significant digit;  
Coffee to water brew ratios aren't that sensitive.  Plus or minus 3% in either or both won't make a difference in the cup.  That is, a 15% brew ratio tastes a lot like a 17% ratio.  Depending on the brew method other factors like steep time, grind size, agitation and brew temperature are far more apparent on the palate;
If you can't calculate water volume to water weight conversions within the limits of useful accuracy, either you're arithmetically challenged, or I'm a savant.*  That goes double, when working within the limited range of coffee brewing, and treble after you've had some practice with your brewing equipment;
For Chemex + Kone, Espro and Siphon I eyeball the water into the 1L kettle -- 1L for Chemex, 1L for Chemex, 0.9L for Siphon.  I fill my six(!) non-Espro "eight cup" presses until the "bloom" is just short of the rim.  The Aeropress is also a known volume.  Of course there's some slop in the "measurement," but the coffee is very consistent; and finally
Who here puts a measuring cup on a scale instead of just using the graduate marks?  If so, why?  What difference do you suppose it makes?  

Rich

*I'd be an idiot savant, but am not a savant.

Posted March 3, 2014 link

Rich, I don't think the intention is to "bust your balls", irrespective of whether we are talking hot/cold brew, the point is really to be consistent in the way you measure brew water, if you do it cold, stick to doing it cold, etc.

As Andy said, it's relevant if measuring extraction. I'm assuming (perhaps incorrectly) you meant that the difference between 15:1 and 17:1 wouldn't make a difference? This is a bigger discrepancy than that previously mentioned and it equates to either being smack dab in the middle of the SCAA box, or being 1% ext yield clear outside it (+/- 3% ext. yield). If you are going by taste you could well be attributing differences in flavour to a bean/roast, rather than identifying that you are extracting to significantly different levels. Even if the difference outlined by Andy isn't a huge deal on it's own, (if brewing at one ratio consistently rather than flitting between two, going by taste) there are other factors that can compound the error.

I'm terrible at mental arithmetic, so if in doubt I tend to stick to multiples of 10g doses, maybe 15g if I'm feeling particularly sharp ;-)

Oh, and I use both, fill to line (pre measured water mass) and brew on scales methods depending on what I'm using & where I am (if brewing a pourover ....and I can imagine your eyes rolling as you read this Rich :-)...I have a brewstand on one set of scales, then a second set of scales on the stand but under the cup, so I can simultaneously measure brew water added & beverage produced).

AndyS, I'm not sure it's fair to lay the error at Lockhart's door ;-), didn't he inherit the brew ratio methodology from the earlier NCA & MRI studies?
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andys
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andys
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Posted Tue Mar 4, 2014, 5:20am
Subject: Re: Coffee ratios
 

MWJB Said:

AndyS, I'm not sure it's fair to lay the error at Lockhart's door ;-), didn't he inherit the brew ratio methodology from the earlier NCA & MRI studies?

Posted March 4, 2014 link

Don't know, I could be mis-remembering what Vince said. But my rule is, if you're going to blame someone, it's always best to blame a dead guy, 'cause he won't complain back.  :-P

 
-AndyS
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jpender
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jpender
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Posted Tue Mar 4, 2014, 1:54pm
Subject: Re: Coffee ratios
 

Andy, that was also in the Nordic talk he gave a couple of years ago.

It would be interesting to read the original work from Lockhart. The old charts are confusing, e.g. with brew ratio in gallons/pound and extraction in terms of ounces/pound. Vince said in his talk that originally the brew water was measured volumetrically at room temperature. If you're using SI units that works okay since the density of cool water is very close to 1 g/ml. But in US units the density is 1 oz/oz just below boiling; cool water is about 1.04 oz/oz. I guess that's where the extra extraction point came from but without seeing what Lockhart actually did I'll just take Vince's word for it.

Heh... the OP wanted to understand what a coffee ratio is.
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MWJB
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Posted Tue Mar 4, 2014, 3:15pm
Subject: Re: Coffee ratios
 

jpender Said:

Andy, that was also in the Nordic talk he gave a couple of years ago.

It would be interesting to read the original work from Lockhart. The old charts are confusing, e.g. with brew ratio in gallons/pound and extraction in terms of ounces/pound. Vince said in his talk that originally the brew water was measured volumetrically at room temperature. If you're using SI units that works okay since the density of cool water is very close to 1 g/ml. But in US units the density is 1 oz/oz just below boiling; cool water is about 1.04 oz/oz. I guess that's where the extra extraction point came from but without seeing what Lockhart actually did I'll just take Vince's word for it.

Heh... the OP wanted to understand what a coffee ratio is.

Posted March 4, 2014 link

John, the old charts are just the same as the current SCAA chart, just unit sizes are revised/metricated...

The earlier chart comparing NCA & MRI studies shows a ~2.1gal/lb brew ratio (not great definition) roughly intersecting the MRI ideal box around 1.15% TDS & 18% yield (454g/7.948.5l = 57g/l). The SCAA chart shows an equivalent line at 106g/1.9l = 55.8g/l (but half a gal weighs 1892.5g so 56g/l), in turn based on the CBI/CBC chart of 2.15-ish gal/lb brew ratio (55g/l) and the start of the ideal box at 2.875oz/lb ext. yield (2.875/16 = 17.97%). It's just the syntax that changes. They all show the same thing...~56g/l as the line that intersect the box at 1.15%TDS @ 18% ext. yield and exits at 1.35%TDS @ 21% ext yield.

1.000l/56g = 17.9:1.
1.8925l/106g = 17.9:1
8.138l/454g (2.15gal/lb) = 17.9:1.
The CBI recommended scoop was nominally 10g/30ml/1fl.oz to be brewed with 6 fl.oz of water = ~18:1.

This appears to be the CBI/CBC's golden ratio, subject to grind & brew time recommendations to achieve landing in the box (55-56g/l giving you the largest range within the box, 55-56g/l also pretty symmetrically divides the earlier NCA ideal box of 1.04-1.39%TDS @ 17.5 to 21.2%, but does not hit the min/max concentrations). As the 56g/l line exits at ~21%, 19.5% ext yld, or just a shade over, is the midpoint extraction-wise...at least that's my, possibly unique, reading of it. ;-)
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jpender
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jpender
Joined: 11 Jul 2011
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Posted Tue Mar 4, 2014, 8:34pm
Subject: Re: Coffee ratios
 

MWJB Said:

John, the old charts are just the same as the current SCAA chart, just unit sizes are revised/metricated...

Posted March 4, 2014 link

Duh... I get confused sometimes. Of course you're right. I had even gone through this exercise with the old charts myself some time ago.

MWJB Said:

18.138l/452g (2.15gal/lb) = 18:1

Posted March 4, 2014 link

That last step, the conversion from volume/weight to dimensionless ratio, depends on the temperature. It's 18:1 if you measure the volume of water at room temperature but it's about 17:1 if you measure it at brewing temperature. Now I think Vince said that those old guys measured the volume at room temperature sometimes and at 140°F other times. But I don't understand how he determined that the old charts were about 1% too high in extraction because of this temperature/density issue.

Can you explain this?
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MWJB
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Posted Wed Mar 5, 2014, 3:26am
Subject: Re: Coffee ratios
 

jpender Said:

Duh... I get confused sometimes. Of course you're right. I had even gone through this exercise with the old charts myself some time ago.


That last step, the conversion from volume/weight to dimensionless ratio, depends on the temperature. It's 18:1 if you measure the volume of water at room temperature but it's about 17:1 if you measure it at brewing temperature. Now I think Vince said that those old guys measured the volume at room temperature sometimes and at 140°F other times. But I don't understand how he determined that the old charts were about 1% too high in extraction because of this temperature/density issue.

Can you explain this?

Posted March 4, 2014 link

Yes & no ;-)

Firstly, the ext yield skipping to the left only occurs in certain, specific circumstances, in others it can stay where it is, skip farther left, or even possibly skip right!

As both you & Andy point out, it was Vince who identified this as one of the errors in the old method, it was his innovation to make certain corrections as they hadn't been formally done prior. It wouldn't be right for me to break down his work. The important aspect is to stick to one or the other (hot vs cold measurement), especially if analysing TDS/yield as Andy said earlier (if brewing by taste then the difference isn't "go/no go", you can still make the normal adjustments in grind to hit an ideal yield). I don't mean to appear evasive, or that I am protecting some mysterious coven, just that all the references regarding this aspect all go back to Vince's Nordic Barista talk, which I understand was only made public for a short period due to a licencing agreement. I think there is some misunderstanding, maybe even suspicion regarding the disappearance of that talk, the reality is more that we were briefly allowed the priviledge of certain insights, that were not widely acknowledged prior.
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jpender
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jpender
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Posted Wed Mar 5, 2014, 10:58am
Subject: Re: Coffee ratios
 

MWJB Said:

Firstly, the ext yield skipping to the left only occurs in certain, specific circumstances, in others it can stay where it is, skip farther left, or even possibly skip right!

Posted March 5, 2014 link

In this case I'm asking specifically about the extraction yield target for drip coffee as determined ~50 years ago by Lockhart.

MWJB Said:

The important aspect is to stick to one or the other (hot vs cold measurement), especially if analysing TDS/yield...

Posted March 5, 2014 link

This makes no sense. If you measure the extraction yield you're measuring mass/mass. It's true that temperature can affect the measurements needed to calculate it but it won't change the extraction yield itself. And if we're to believe what Andy posted above, Vince discovered that Lockhart (a chemist) made what sounds like a high school chemistry error. I'm just curious to know exactly how Lockhart goofed. Is that classified?
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MWJB
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Posted Wed Mar 5, 2014, 1:53pm
Subject: Re: Coffee ratios
 

jpender Said:

In this case I'm asking specifically about the extraction yield target for drip coffee as determined ~50 years ago by Lockhart.


This makes no sense. If you measure the extraction yield you're measuring mass/mass. It's true that temperature can affect the measurements needed to calculate it but it won't change the extraction yield itself. And if we're to believe what Andy posted above, Vince discovered that Lockhart (a chemist) made what sounds like a high school chemistry error. I'm just curious to know exactly how Lockhart goofed. Is that classified?

Posted March 5, 2014 link

You say that the extraction yield target relates to drip coffee. Why do you say that specifically? The brew ratio advocated by the CBI/CBC was suggested with regards to popular brewers of the day. It works for drip & other methods, as long as they adhere to certain parameters (even drip doesn't always). You can get fairly close to an accurate reading by emulating exactly the methods & masses suggested by SCAA/SCAE. From the measurements & ratios in my previous post, you can see approx +/-1g/l swing depending on units used...measuring to the decimal point of an ext. yield doesn't seem to have been a priority, it seems more about just getting in the box as a whole, an everyday guide for industry & home?

The target yield range still stands after all these years (unless you have an EK43, even without one certain folk/tastes advocate specific yield ranges within the box as more desirable than others, some folk have preference/do not reject yields just outside the lower limit), but the research was done by other agencies then adopted by/supplied to Lockhart, I guess he concurred with it, otherwise we'd have a different chart.

The CBI/CBC advice isn't necesarilly, or always, an "error", it mostly follows the method/protocols that they used then. Today with more attention paid to precise measurement and narrowing down the super ideal ranges wthin that ideal range, different brewers & protocols, the chart needs re-jigging in a lot of cases. Vince's contribution isn't a mere reworking, or confirmation of Lockhart's work, it's significant stride forward from that.

It's not clear to me whether Lockhart was responsible for the brew ratio protocol that they adhered to, or whether he inherited it from the studies actually carried out by the National Coffee Asociation, or Midwest Research Institute, both of which the CBI/CBC used for their chart(s). Vince would probably know better than me? The CBI/CBC also appeared to be busy with educating the public as to best practices in brewing (re. time & grind) & assessing products brough to market, to ensure that they conformed to a standard.

Again, much of this is particularly relevant to accurate measurement & assessment. If you're brewiing by taste & not trying to specifically hit a pre determined target, +/- a couple of g/l isn't going to make or break.
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