Posted Thu Aug 9, 2012, 6:07am Subject: Investigating the Brewing Control Chart
Find copies of it on Bunn's site, or mountaincitybrewing. These calculations are not secret - everyone knows how to calculate strength and extraction. also available: http://scae.com/images/PDF/coffee_brewing_control.pdf
So, today I thought I'd share my last batch of tasting experiments.
YMMV - taste is very subjective, but I think I've tasted enough of the "space" to tell the differences between underdeveloped (I don't like the term "under-extracted"), and over-developed.
I used a fixed amount of brew water, and did most of these comparisons between an auto-drip (Melitta BCM-4C) and something I call "Mason Jar / AeroPress" brewing. The latter is what you think - combine in Mason Jar, timed infusion, dump into an AeroPress with a filter and separate. Basically a larger version of "cupping" with full control over the brewing variables.
Strike temperature for the MJA brewing was 200°F-204°F.
I was interested in a couple of questions:
-Is there a difference in taste between the two methods? -Does the brew ratio have the same relationship to strength given a particular set of brew parameters? -If there is a difference in taste, what has to change to make them taste the same?
First off - the traditional brew chart, like what is found on mountain city's site, as well as the freely-available Bunn brewing guidelines, are based around an absorption of approximately 2. (see previous discussion on how I define absorption). Depending on the assumptions, this may or may not be correct - the brew water amounts are expressed in volume - but at an undefined temperature. I base all of my brew ratio in mass - making the brew ratio consistent and unitless, independent of temperature.
If you look at the middle of the sweet spot: 1.25% strength and 20% extraction, at a coffee amount of around 54.7-54.9g/liter on the chart, the back calculated absorption is completely dependent on whether that liter is measured at 42° (1000g), 72°F (997.7g), 195°F (964.9g), 205°F (961.1g), or at sea-level boiling minus a bit - 211.9°F (958.4g).
Rarely is the displacement water in a Bunn, or the water you pour into a reservoir of an auto drip actually measured at brewing temperatures - but there IS a difference. The Bunn, for example, uses a hot water tank displacement to deliver constant temperature water. Pour in 1 liter (1000g at room temperature), and more than 1 liter comes out of the tank - because that 1000g you put in to start the brew cycle displaces the same mass of water in the hot water tank, which then begins to heat up - and expand. This will result (evaporation notwithstanding) in slightly more than a liter, (but pretty much 1000g) becoming the brew water. Since this is usually ambient or tap water (58°F - maybe 70°F), I call it sufficiently close to normal max density of water (1g/cc) that 1 liter ~ 1000g.
See why using mass is much cleaner?
So, call the sweet spot achieved at a water brew ratio of 18.25g water per gram of coffee. Bottom line - if you use ambient temperature water, volume in cc ~ grams. If you (for whatever reason) measure your brew water hot - this will have an effect on the calculations.
As I stated before (and not a secret by any means):
Coffee Produced = Brew Water - (Absorption * Brew Coffee) - evaporation
Absorption and "effective" water brew ratio are best obtained at the end of brewing, where you measure the wet grounds and the produced coffee.
Unless your brewing method loses grounds or brewed coffee, the mass of coffee is preserved (Netphilosopher's theory of Brew Coffee Mass Conservation ;^D ) This mass of coffee will be present at the end of brewing, dissolved or undissolved, in the spent grounds or in the produced coffee.
My BCM-4C true absorption is right around 1.7. The AeroPress averages about 1.3.
My first start was a pair of brews with common goal of same strength (1.25%) using same water brew ratio (18.25).
This was really much more difficult than I imagined. It took multiple adjustments on the BCM-4C with grind level until I achieved it:
400g (net) Brew Water 21.9g Brew Coffee
Grounds = 59.2
Cp = ~363g
S = 1.25%
If you want to calculate "extraction", you can use the brew chart (20%, based on absorption of 2.2, the intersection of 1.25% strength and 104.1g/1.9liters), or you can calculate it based on yield (363 * .0125)/21.9 = 20.7%.
What it tastes like: fairly bitter, trending toward overextracted, astringent. Surprising. Here was the definition of the legendary 20% extraction, brewed to obtain parameters on the traditional brew charts - yet it's something that was starting to turn toward overextraction.
Regardless, I forged on.
MJA brewing: worked with a 6 minute contact time in the Mason Jar (to achieve stabilized strength), then pour the slurry into the AP to press the results.
Immediately, if I used the same grind as the BCM-4C, I undershot the strength by a tremendous amount. It took grinding to quite fine before I achieved a yield strength of 1.25%
250g Brew Water 13.7g Brew Coffee
G ~ 31.0 Cp ~ 232g
S = 1.25%
Extraction calculations are 20% according to the brew control chart (same brew ratio, same strength), but a yield-based extraction of (232*.0125)/13.7 = 21.2% extraction.
What it tasted like: absolute crap. This was getting toward horribly bitter, definitely overextracted coffee. Pretty bad. Keep in mind that this is not really a viable brew in a press pot, as the fineness of the grind would let probably half the coffee through the filter.
So, the next question in my mind is what would it take to march the BCM-4C toward recognizable "underdeveloped" brews at the same strength, and where is the sweet spot?
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Posted Thu Aug 9, 2012, 6:53am Subject: Re: Investigating the Brewing Control Chart
BCM-4C is a great little brewer.
I began walking the grind coarser and coarser with the same water brew ratio (18.25), but the problem with that was the resulting strength would start dropping. I decided to target brew chart extraction levels at 1.25% strength for 19%, 18%, and 17% extractions. Looking up on the charts, these would require brew ratios of 17.4, 16.6, and 15.8 respectively.
Simple, right?
Nope. It took darn near a lb of coffee to get these zoned in exactly. Each step began with a brew with a change in grind - obtain a strength, then adjust the grind until correct strength achieved. This took a few weeks.
The 17% target took the longest to achieve - I eventually had to use the coarsest grind and hot reservoir water to reduce the total brew time.
In the end, it was setting up the brew ratio, then adjust the grind to achieve the strength target.
19% target BCM-4C 400g Brew Water 23g Brew Coffee
Grounds ~62g
Cp ~ 360g
S = 1.25%
By definition on the brewing control chart, this was a 19% extraction. By yield (360*.0125)/23 = 19.6%.
I rather enjoyed this cup of coffee. Nice, balanced. Not really bitter, decent and fairly smooth.
18% target BCM-4C 400g Brew Water 24.1g Brew Coffee
Grounds ~ 63g
Cp ~ 358.7g S = 1.25%
By definition, 18% extraction. By yield: (358.7 * .0125)/24.1 = 18.6% extraction.
I liked this cup too, maybe a bit more. A bit smoother than the "19%" batch. Maybe a touch less bitterness, and some surprising fruity notes (this is, of course, just EoC 100% Colombia). A noted increase in the flavor toward "sweet". I think this might actually be one of my target zones - having tried this on some Costa Rica and also some Yirg - this seems to really be a good "sweet" (literally) spot for my personal tastes. To get here, I had to use the coarsest grind on the Bodum Bistro. By eye, this is somewhere around 800micron, and did show some channeling of the grounds as evidenced by small showerhead holes in the surface of the spent grounds.
17% target BCM-4C 400g Brew Water 25.3g Brew Coffee
Grounds ~ 68g
Cp ~ 356.5g
S = 1.25%
Again, by definition 17% extraction. By yield: (356.5 * 0.0125)/25.3 = 17.6%
This was a very acceptable cup. I did have to go through extraordinary measures to get here - hot water and a short brewing cycle on coarsest grind. I find this also surprising - nothing like the elements of underextraction I've seen in the past - no earwaxy flavors, no sourness. By all accounts, this should be underextracted, and if it is by taste, it is JUST so.
Just the auto drip portion alone was worth the time invested. Ya never know what you'll encounter.
If I had to pick, I'd say the 18% target/18.6% yield is the best of the three brews (16.6 water brew ratio). This also shows some on the board about my methodology: set your water brew ratio, THEN adjust the grind with a consistent brew process until the desired strength is achieved.
In the process, I've had stronger brews with all three brew ratios:
with 17.4 water brew ratio, it starts picking up significant bitterness at strengths around 1.35%, and definitely nasty above 1.40%
with 16.6, these ranges shift up by about 0.05 to 0.07 (picks up bitterness around 1.41%, definitely over at 1.46%)
At 15.6, it's around 1.46% and definitely gone by 1.55% or so - but it's pretty noticeably strong at that point.
I was surprised at how these ranges are quite shifted to the classic "sweet" spot still taught today.
Next up was what brew ratios were necessary at 1.25% strength using the MJA method to achieve similar tastes.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Posted Thu Aug 9, 2012, 11:17am Subject: Re: Investigating the Brewing Control Chart
And.... nothing is ever easy.
First off, every time a brew is set up with a particular brew ratio and similar grind to BCM-4C(drip) for in the MJA brewing method, the resulting strength is ALWAYS lower.
Secondly, at 6 minutes steep and equilibrium, I still get (much like the BCM-4C) pretty strong coffee. I have to use cooler temperatures or terminate the brew earlier to achieve "underdeveloped" notes on the coarsest grind possible.
This process took even longer. I went a couple of false starts until I honed in on my method: Set to same brew ratio ranges as the BCM-4C at the various targets, then adjust grind to achieve 1.25% strength. Then, if necessary, keep investigating each extraction target lower.
From the Brew Chart, looking along the 1.25% strength line:
19% Extraction ~ 17.4 water brew ratio 18% Extraction ~ 15.8 water brew ratio 17% Extraction ~ 15.0 water brew ratio 16% Extraction ~ 14.2 water brew ratio 15% Extraction ~ 13.4 water brew ratio 14% Extraction ~ 12.6 water brew ratio
So, for the 19% Extraction target, use 17.4 water brew ratio: 250g Brew Water 14.37g Brew Coffee
Cp ~ 231g at 1.25% strength.
Again, since this was set up using the brewing control chart, it is by definition 19% extraction using that method. Yield-based calculation is right around 20% extraction.
What it TASTES like: Pretty bitter, still. Drinkable, but barely. Fairly astringent. Tastes... overextracted.
I won't bore everyone with the details, all these evaluated at a yielded strength of 1.25%:
17.4 water brew ratio, 19% Brew Chart / 20.1% Yield-based extraction, Tastes overextracted. Not "maybe". It tastes clearly overextracted.
16.6 water brew ratio, 18% Brew Chart / 19.0% Yield-based extraction, tastes strong, nearly or slightly overextracted, and slightly bitter, like it was on the edge of turning to overextracted. Similar to the 17.4 Water Brew Ratio BCM-4C drip.
15.8 water brew ratio, 18% Brew Chart / 19.1% Yield-based extraction, Decent. Slightly astringent - just a hint, and a bit of smoky bitterness, but very faint. A bit more "extracted" than I'd target, and lacks some of the sweetness or it is masked by some slight bitter taints.
15.0 water brew ratio, 17% Brew Chart / 18.0% Yield-based extraction, Darn good. Nice, smooth. Pretty darn close to the "sweet spot". Balanced, hints of good fruity character and a touch of sweetness. Not bitter. I've kinda moved to this brew ratio in my CCD brews since I did this study. (about 420g water : 27g coffee coarsely ground, 3:00 contact time or so)
*14.2 water brew ratio, 16% Brew Chart / 17.1% Yield-based extraction, Still pretty good, nice and smooth but a bit "simplified" for lack of a better word. Most people would consider this an excellent cup of coffee, but it is lacking some of the hearty character I expect.
*13.4 water brew ratio, 15% Brew Chart / 16.0% Yield-based extraction, Starting to take on elements of sourness, or I call "earwax" - a cross between bitter notes and sourness. Some Lipton tea-like notes (reminiscent of cold brewed coffee), and some sweetness but a fairly misbalanced flavor profile. Definitely missing something.
*12.6 water brew ratio, 14% Brew Chart / 15.2% Yield-based extraction, I'd have to say this is probably a really good definition of "underdeveloped". Not completely unpleasant, but there is a distinct slight earwaxy-tartness, and a strong and distinct impression of being more tea-like than coffee like. A chunk of the coffee character is slighty off or absent.
*I did have to go to modified measures to achieve 1.25% strength with these asterisked brew ratios - I just ended up making them in the AeroPress directly, bypassing the Mason Jar because for the strong brew ratio there wasn't enough time to incorporate, make sure the slurry was fully wetted and grounds were beginning to sink. Brewing termination was ~3:15 minutes with maximum grind for 14.2, 2:35 for the 13.6, and 1:15 for the 12.6 brew.
Bottom line: For my automatic drip, a 16.6 water brew ratio works very well if I achieve 1.25% strength, but there is a tendency for the system to over-extract. I have to use a slightly coarser than expected grind for a drip, but it works and tastes very good.
For my CCD, I use 15 water brew ratio. That's about 400g brew water to 26.7g brew coffee for the CCD coarse grind, ~4 minutes, then press (or release). Keep in mind that single cup servers are fairly sensitive to variation - just going from 400g brew water to 425 means you have to increase your coffee by over 1 1/2 grams, and yes it matters.
Same brew ratio for my press pot: ~825g brew water : 55g brew coffee, but also find that if I do a full 6 minute steep, the coffee can be on the over-extracted side somewhat. I will sometimes terminate the brew at 4 minutes OR lower the strike temperature to about 190°F, depending on my mood.
The feedback is pretty quick - if you hit 1.25% strength in the cup, it worked.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
here is how I picked the brew ratios, different extraction levels and desired strength (1.25%). If you lock down the brew ratio, and achieve the target strength, then you achieve the extraction according to the brew control chart, complete with the assumptions on how brew ratio is calculated AND an assumed absorption.
(Click for larger image)
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Posted Thu Aug 9, 2012, 11:52am Subject: Re: Investigating the Brewing Control Chart
Here's an illustration of my new personal "sweet spots" that result in very similar flavor profiles.
Your personal taste buds will vary.
(Click for larger image)
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Posted Fri Aug 10, 2012, 5:21am Subject: Re: Investigating the Brewing Control Chart
Ok, so answering a couple of questions I received over the last day (those of you who received my email know I'm addressing them in the forum).
-About my last post topic (which doesn't exist): I don't know. You'll have to ask Mark Prince. Beats me why.
-About these last posts in this topic: I post these because I think that people may benefit, and it provides a framework less based on opinion and more based on objective measurement. I post these so that people who are so inclined can duplicate, objectively comment. I'm building a full theory of coffee extraction and that means posting results openly so that others can build on, or refute results. All theories are first and foremost falsifiable. Yes, it's a lot of work. No, I'm not afraid of people stealing my work because anyone can do this stuff. The brewing control charts are openly available online through numerous sources. Anyone can borrow or obtain copies of Illy's book, Rao's book (which is informative but light on tech details, but outlines the current thinking on "extraction"), Lockhart's writings, etc. HOW to calculate "extraction" isn't a secret.
There is the assumption that the Lockhart Sweet Spot is rock solid - it most certainly is not. Some people like 20% extraction - but when you get a difference between a chart and a calculation, then something's not right. Other's love coffee at 1.5% or 2.5% strength. 20% extraction for one method doesn't necessarily apply to another.
20% extraction (brew chart or calculated) may not be applicable for yield strength above the upper end of the brewing control chart, 1.8% or 2.0% (something I'm finding for personal taste - I like lower calculated extraction for higher brew ratio).
Rarely do I see organized home-based research into these questions. Maybe my posts inspire others. It's a labor of passion (some would say obsession).
One can always skip the posts. :^D Not twisting anyone's arm to read these posts.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Posted Mon Aug 13, 2012, 4:10am Subject: Re: Investigating the Brewing Control Chart
Interesting finding while doing this with my auto drip - it appears a delivery cycle of ~200-250 seconds is a really good sweet spot.
In an automatic drip machine, this is controlled by two factors: total amount of reservoir water and the temperature of the reservoir water.
My BCM-4C really likes 400-425g, a delivery cycle of around 220 - 260 seconds with ~70°F water.
The kool thing about this is once you understand your auto drip brewer, you'll realize there are two constraints:
1) the time it takes to deliver a certain amount of water, and 2) the size of the basket.
Either one will point the direction for how much water and coffee to use - by utilizing a brew ratio that works.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Posted Thu Aug 16, 2012, 12:00pm Subject: Re: Investigating the Brewing Control Chart
I beg of you - those that really get into the geeky side of the brewing process, please please please for the love of the world:
PLEASE do your brewing calculations in mass.
The metric system is even better - at room temperature, 1 ml of water is basically 1 gram.
1 fluid oz is NOT 1 oz of weight in water - EXCEPT at 210.73°F. 1 fluid oz of water at cool or room temperature is actually 1.04 oz of weight in water.
I spent a couple of hours last night unraveling the intricacies of the brewing control chart(s). Talk about issues with unit conversion - it's no wonder we lost a Mars probe due to unit conversion errors.
Bottom line, the brew chart works for an absorption of 2.0, only if you use the brew ratios they state at the valid temperature (generally between 80°F and 110°F). Why use volume at all - scales are cheap and accurate nowadays.
Gritty details in following post.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Posted Thu Aug 16, 2012, 12:07pm Subject: Re: Investigating the Brewing Control Chart
On the surface, unit conversions seem simple, yes? Well, even the SCAA brewing chart is confusing.
At least the SCAE brewing control chart has some sense to it - because they only have one measurement system.
The water mass brew ratio is easily calculated if you have a known point for defining the brew water mass (not volume!).
Reconstructing the SCAA/SCAE brewing control charts needs to have the absorption defined, but the other inconsistency is the brew ratio. The amount of coffee is well defined (as a weight for English, and a metric equiavalent on SCAA, and mass of coffee in grams for SCAE)
However, it really gets messed up with mass and volume of the brew water, especially when it comes to converting fluid oz. The brew charts for SCAA have values for both oz coffee per 64 FLUID oz of brew water, but then there's a conversion for grams coffee per 1.9 liters of water. Here is the clue as to what temperature the brew chart is valid.
There are really only two densities that are relevant:
1) the density at the temperature where 64 fluid oz = 64 oz avoirdupois (that's 210.73°F, where 1 fluid oz = 29.57353 ml, but has a mass of 28.35g, which is 1 oz avoirdupois, and the density is 0.9586 g/ml), and,
2) The max density of water at 4°C/39.5°F where 1ml = 1g, but 1 fluid oz = 1.043 oz avdp. This is sufficiently close to 1 from freezing to about 100°F (0°C - 40°F), or density of 0.993 g/ml or higher (up to 1.0).
4.75 oz of coffee = 134.66g of coffee. Pretty straightforward.
64 fluid oz at 210.73°F is 1892.71 ml and has a mass of 1814.37g. Water Brew Ratio = 1814.37/134.66 = 13.47 64 fluid oz at 40°F is still 1892.71 ml, but has a mass of 1892.71g. Water Brew Ratio = 1892.71g/134.66 = 14.06
On the SCAA charts, they provide a conversion that is a normal conversion for the coffee mass - and it should be.
There's no ambiguity here - 4.75 oz of coffee IS 134.66g. Some charts round off to 135g.
The problem is 1/2 gallon or 64 fluid oz is only 1892.71 ml - so there's already a small descrepancy, since they call the reference brew water "1.9 liters" or 1900ml, but same amount of brew coffee. Last I knew, 1900 milliliters DOES NOT EQUAL 1892.71ml...
...regardless:
1900 ml at 210.73°F is 1821.4g, Water Brew Ratio = 13.53 1900 ml at 40°F is 1900g, Water Brew Ratio = 14.11
To get these fairly spot on, there is no temperature where 1900ml = 1814.37g, but there is a temperature where 64 fluid oz = 1821.4g:
1900 ml at 210.73°F = 64 fluid oz (or 1/2 gallon) at 201.4°F = 1821.4g, where the Water Brew Ratio is 13.53
At the lower end, there is no temperature where 64 fluid oz ever has a mass of 1900ml, but there is a temperature where 1900ml = 1892.71g:
1900 ml at 83°F = 64 fluid oz (or 1/2 gallon) at 40°F = 1892.71g, where for 134.66g of coffee, the water brew ratio is 14.06
The density of water at 210.73°F is 0.9586 g/ml (and the temperature where 1 fluid oz = 1 oz weight) The density of water at 201.4°F is 0.9623 g/ml (and pretty much the target brewing temperature) The density of water at 83°F is 0.9962 g/ml The density of water at 40°F is pretty much 1.0 g/ml
You can pick a known point that locks down the brew ratio, strength and extraction and mathematically calculate the required absorption to achieve that yield.
On the SCAA chart, 1.30% strength and 19% extraction are achieved at a brew ratio of 4 oz / 64 fluid oz or 113.4g/1.9 liters.
For the hot-measured volumes: 1900ml at 210.73°F or 64 fl oz at 201.4°F, the Water mass brew ratio is 16.06 - to achieve the 1.30% strength and 19% extraction, absorption must be 1.45.
1900ml at 83°F or 64 fl oz at 40°F, the water mass brew ratio is 16.7 - to achieve the 1.30% strength and 19% extraction, absorption must be 2.07.
On the SCAE chart, there is an intersection with 65 grams of coffee per liter, strength = 1.35% at 18% extraction.
1 liter has a mass of the following:
958.6g at 210.73°F 962.3g at 201.4°F 996.2g at 83°F 1000g at 40°F
The following brew ratios for 65g of coffee at the different masses are: 14.75 at 210.73°F 14.80 at 201.4°F 15.33 at 83°F 15.38 at 40°F
The absorption values to achieve 1.35% strength and 18% extraction are: 14.75 at 210.73°F, absorption = 1.41 14.80 at 201.4°F, absorption = 1.47 15.33 at 83°F, absorption = 1.99 15.38 at 40°F, absorption = 2.05
Which one is actually the most correct?
Well, actual MASS absorption on a drip brewer is somewhere between 1.65 and 2.4 based on my experience. On average, and dependent on the brewer, it's probably safe to call it 2.0 even for calculating ease - it's closest to something around the original intention of the brewing control chart. We rarely measure a volume of water at the moment it is ready to be poured.
From the above work, it's the brew ratio calculated as if the water were "around" room temperature. To get the exact conditions to make each of the brew ratios whatever is needed to achieve 2.0 absorption:
For the SCAA chart (1.30% strength / 19% extraction, A = 2), required Water Mass Brew Ratio is 16.615 For 4 oz of coffee (113.4g), you would need 1.9 liter at 107°F, 64 fluid oz (1892.71ml) at 87°F, or 1884.15ml at 0°F (or 1884.15g, same thing).
For the SCAE chart (1.35% strength / 18% extraction, A = 2), required Water Mass Brew Ratio is 15.33 For 65g of coffee, you would need 1 liter of water at 80°F or 996.7g of water. Actually, you're probably close enough with a liter of room temperature water.
But just get your brewer on a scale, MEASURE THE MASS OF IT when you brew, and be done with it. If you're using a drip coffee maker - all the easier, just weigh the water and dump it into the reservoir. Mass is independent of temperature - so measure out the mass and you'll be much more accurate than anything volume will be.
This is all before taking into account the variation in actually measuring VOLUME. A 1 liter press pot like my Bodum Shin Bistro has a diameter of about 95mm. For every millimeter you are off on the level of water, this is an error of 7ml - the variation in miniscus alone is probably close to 2 mm - so right there you can get about 1 liter +/- 10ml. That is actually not that great for error.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Posted Thu Aug 16, 2012, 12:39pm Subject: Re: Investigating the Brewing Control Chart
And please use a scale for the amount of coffee.
1 level tablespoon of coffee depending on the density and packing, is anywhere from 3.8 to almost 7.5g. A scoop isn't always a scoop - the scoop that comes with an AeroPress is around 40ml, and this can be anywhere from (correction) 11g to 16g - IF LEVEL.
Add the term "heaping" and you can end up with another 20% to 40%....
If you are trying for a brew ratio of 15, and you use "about" 405ml, this means you'll have somewhere between 390g to 415g if you do it around room temperature and have a typical measuring cup and try to do it by volume. Try it yourself - pour out 405ml and see how close you get to 405g - it's harder than you think.
And if you use the 5g/tablespoon equivalent that is stated in various places around the internet, you need 27.0g of coffee. That's 5 tablespoons, but if you have a light roast coffee that's fresh (i.e. with lots of CO2), and you maybe do a bit more than level (not heaping, but who has time to get exact here?)... you might end up with 35g of coffee. Or if you use old dark-roasted coffee with little CO2 left, and you're really diligent about getting exactly level tablespoon scoops, you might end up with only 22g of coffee.
Your resulting brew ratio might range anywhere from 12 to 18 - when you were targeting 15. Does it make a difference?
15 brew ratio, achieving 20% extraction means about 1.54% strength. 12 brew ratio, achieving 20% extraction means about 2.00% strength. 18 brew ratio, achieving 20% extraction means about 1.25% strength.
Consider that the SCAA strength target ranges are ~1.15-1.35%, and European (SCAE) target range is ~1.25-1.45%, the variation with careless use of volumes instead of the more accurate mass is huge.
Just measure the mass of your coffee. You'll be much more accurate.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
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