Manual brew method consistency – further thoughts…

The various coffee associations depict ideal extraction boxes of a 4% span of extraction yield, all centred at 20%EY, encompassing 18-22%EY (although this standard actually goes back six decades). For a given brew method, how achievable is this across a range of coffees?

Several tests of 10 brews each, a different coffee for each brew (within my typical preference, e.g. various recent roasts from speciality roasters, not going from the lightest of the light to supermarket, old, dark  roasted coffee sat on the shelf for months), shows that this range of 4% EY should be your absolute minimum target for your default grind setting & recipe. In fact, to achieve 95/100 brews in this range, 10 reference brews would typically need to fall within a 3%EY span & a standard deviation of ≤0.88%EY.

If you cannot keep the vast majority of brews within this range, assess your method, look at how you can reduce margin for error (careful weighing of dose/brew water/finished beverage & timing – repeating each step the same way, as much as possible, for each brew). Establishing whether or not you are achieving this is going to be very difficult without measurement.

With care, a standard deviation of ≤0.66%EY is certainly possible, suggesting the vast majority of brews, across different coffees, landing ±1.5%EY. This is without changing any aspect of the recipe, including grind setting.

Singling out a single coffee reduces variance further, a standard deviation of ≤0.5%EY is certainly achievable with care. For example, using the V60 recipe in the previous post (weighing brew water and killing the finished brew to the gram in the cup), 10 brews gave me a standard deviation of 0.34%EY, with 8/10 of the brews spanning 0.01%TDS (this is smaller variance than the precision specification of my VST Lab II).

I’m aware that there are differing views on the relationship between brew time and consistency of extraction, but these 10 brews all fell within a 15 second total span, with a standard deviation of 4.4 seconds (or, 3% of the flow time post bloom until no liquid standing above the bed). However, I wouldn’t discard, or write off a brew, based on time – always taste & assess, different coffees may take different times to reach the same EY.

Why is this relevant? Well, like many home brewers, I am regularly changing coffees. I want as little waste & disappointing cups as possible. I want to make as few & as small adjustments as possible, to maximise the strike rate of good cups. In short, I want to be able to spend less time chasing down variance from coffee to coffee & more time relaxing & enjoying good coffee. A little groundwork up front, evaluating your brew method & recipe, can pay off in the long run.




Hario V60 Recipe for 1 mug (~200g of brewed coffee), light/medium filter roasts.

This is a recipe that should result in a sweet & balanced cup of coffee. If you are not achieving that, check that you are ending up with the desired brewed weight (a brew stand, with a second set of scales under the cup to measure brewed weight, is a great help here).

If  you have any doubts about the suitability of your water for coffee brewing, use Volvic. Boil twice as much water as you will need for the brew (450g in total).

Grind & then weigh out your 13.5g coffee dose. Grind size should be that which results in the target brew time, err on the coarse side. Place the coffee dose into the brewer & filter paper (Japanese, bleached white, V60 papers recommended).

Preheat your pouring kettle (if not using it to heat the water), start the brew with boiling water, or water that is still rolling when added to the preheated pouring kettle.

Start timer & pour 15g of brew water onto the dry grounds & quickly stir to wet all the coffee. Wait until 30 seconds shows on the timer, then add another 35g of brew water every 20 seconds. Each pour should take around 10 seconds. Pour in spirals, not lingering in any one spot, wash down the filter walls with the tail end of the pour.

If you overshoot/fall short a little on the weight for a pour don’t panic, or throw out the timings by trying to nail water weight exactly to the gram, just make up the weight difference at the next addition of brew water. Ultimately, hitting 225g total (+/- a gram or so) around 2:20 is more important.

Stop the timer when you see the last of the liquid drain from above the bed of grounds, but do not disturb the brewer until the dripping has all but stopped, maybe another 40 to 60 seconds? You should see around 195g to 205g in the cup.

(EDIT: Final weight in the cup may vary slightly depending on your scales’ response characteristics, so I’d only expect to see a gram or two difference between brews with 225g of brew water & the same scales, brew to brew. The larger +/-5g tolerance allows for use of different scales, you shouldn’t see a 10g spread of brewed coffee weights if the same scales are used throughout).

Brewing Pour Guide V60 13.5g to 225g


Chemex 3-6 cup & Hario V60 02 test, alternating filter papers.

A couple of posts back I got some unusual results (compared to contemporary brews) from a Hario V60 02 dripper with a CBI style, drip brew method. I only had Chemex filter papers handy & I wondered whether the paper, or the V60 dripper was responsible for the wider deviation in extractions with that method, compared to Kalitta Wave, Westmark 2-hole plastic (Melitta style) brewer & a Bonavita Immersion dripper (the latter used as a pourover brewer, rather than as an immersion brewer).

It is important to remember that any of these brewers can produce consistent cups with good technique & dialling in. For the purposes of this test however, I was more keen to see how the brewers & papers behaved with a very consistent, but basic technique, with no changes, nor dialling in from the previous tests.

All filter papers were bleached white variants, the V60 papers were made in Japan.

10 brews for each brewer & paper combination were carried out, 40 brews in total. These 40 brews had an average extraction yield of 18.6% and a SDev. of 1.49%EY, the 40 brews spanned a 5.7% range of extraction yields (15.7% to 21.4%).

Chemex & Chemex paper/V60 & Chemex paper vs. V60 & V60 paper/Chemex & V60 paper: showed no significant difference as being due to the paper used, in neither time (p=0.259), nor extraction yield (p=0.097).

Chemex paper & Chemex/V60 paper & Chemex vs. Chemex paper & V60/V60 paper & V60: showed a significant difference in both time (p=0.000) & extraction yield (p=0.003). So it looks like the brewer makes a bigger difference than the paper filter used.

Chemex vs Hario 40 brews

Running an ANOVA on the 4 brewer & paper combinations showed that there was a difference in both brew time & extraction yield.

Further investigation showed no significant difference in extraction yield between V60 with Hario paper, V60 with Chemex paper, or Chemex with Chemex paper. F(2,27)=0.909, p=0.415.

Chemex with V60 paper did show a difference in extraction yield when run over all 4 conditions. F(3,36)=5.960, p=0.002. Note that the Chemex 3-6 cup can brew small amounts with a V60 paper. However, larger brews may see the paper filter & coffee bed slump into the spout’s groove. This will choke the brew, so something in the spout to allow displacement of air in the brewer may be necessary (I have a steel drinking straw that fits nicely).

Hario V60 brewer with Chemex papers, or V60 papers: Whilst there was no difference between the Hario V60 brewer with either paper, in terms of extraction yield (p=0.743), there was a difference in brew time (p=0.000) with the Hario paper taking, on average 18 seconds less to hit the same EY. The V60 brewer did, however, show a lower SDev. (1.10%EY) with the Chemex paper than with the V60 paper (SDev. 1.43%EY).

Chemex brewer with Chemex papers, or V60 papers: There was no significant difference in brew time between Chemex with Hario paper & Chemex with Chemex paper (p=0.768), but there was a difference in extraction yield (p=0.029). The Hario paper in the Chemex brewer resulted in the highest & most consistent extractions (average 20.0%EY, SDev. 0.95%) compared to Chemex paper (18.6%EY, SDev. 1.57%).

Chemex paper with V60, or Chemex brewers: There was no significant difference in extraction yield (p=0.239), but there was a difference in brew time (p=0.000), with the V60 brewer & Chemex paper taking 28 seconds less on average, to hit a similar extraction. The V60 brewer did, however, show a lower SDev. (1.10%EY) than the Chemex brewer with the same paper (SDev. 1.57%EY).

Hario V60 paper with V60, or Chemex brewers: Again this showed the V60 paper & Chemex brewer combination to be able to achieve a higher (20%EY, versus 18%EY for the Hario brewer) & more consistent extraction yield (0.95%SDev, versus 1.45% SDev for the Hario brewer), whilst stretching out brew time by an average of 48 seconds.

Whilst the brew method used, in itself might not follow popular methods, it does seem to reinforce the need to pour in a controlled manner & not allow a large body of liquid to sit above the bed for the Hario V60 with either paper, or the Chemex brewer with Chemex paper.

This test, along with another I conducted with a Bartlett 3-hole (Melitta style) truncated cone, also seems to reinforce Peter Guiliano & Thompson Owens’ observations, that the truncated cone brewers, with a single small drainage hole (Bonmac, Melitta, Bonavita) are able to extract well with a more basic, fill & forget type technique. The Kalita Wave also seems to fall in this category, despite having 3 holes (the holes in my steel 185 version are much smaller than the drainage holes in the other brewers).

My take-aways from this are:

  • Use a goose-neck pouring kettle with drip brewers that have a large and/or numerous drainage holes. Pulse pouring and/or grind adjustments to control flow are more critical for these brewers in order to maintain target extractions.
  • The Kalita Wave & Chemex 3-6 cup, with V60 paper, can produce ‘gold cup’ & consistent extractions with  a regular kitchen kettle. As can the truncated cone brewers with a single, or maybe two, small drainage hole(s).

Purely subjectively, the Chemex brewer & Chemex paper combination achieved the lowest average preferences in this test, but in fairness none of the 4 combinations tested here hit my typical preference, in the context of this experiment.



Manual brew method consistency check.

Is it you, or the, or the recipe, or the brewer itself that is inconsistent?

My recent brew logging excercises pretty much suggest that it is us. Several drip brewers & immersion methods are showing very similar standard deviations in extraction yield, where the same recipe, brewer, grinder & grind setting for that method are used.

Without the need for more in-depth statistical analysis, it is becoming apparent that if you carry out 10 brews, each with a different coffee (assuming all fall within your typical roast preference range), changing nothing but the coffee, a span of <3% extraction yield across those 10 brews is suggestive of 95% of them landing within a 4% EY span. A normal distribution for “Gold cup” brews, if those 10 brews span <3%EY, between 18-22% EY?


CBI Style Drip Brews: Bonavita Immersion Cone, Westmark 6-Cup Cone, Kalita Wave 185, Hario V60 (with Chemex paper).

To recap, all brews were the same dose (13.5g), the same brew ratio (58g/l), the same grinder setting (1+10 on a Made by Knock, Feldgrind).

10 brews for each brewer, the first & only attempt for a different single origin for each brew, in each brewer. Brew water was weighed out into a kettle then poured at a rolling boil, aiming for 232g total brew water added in one, quick (~5 seconds) fill, after blooming.

The ceramic Bonavita Immersion brewer was preheated, filter paper rinsed as part of the preheat. The other brewers (being plastic, or steel) were not preheated, nor were papers rinsed. The Bonavita bloom time ended up at 105 seconds – 90seconds plus fill, then a stir at the surface & open the valve. The other brewers were bloomed for 90seconds, then brew water added, a stir at the surface at completion of fill.

  • Bonavita Immersion cone: Average EY was 20.6%, SDev of 0.61, min. to max. EY span of 1.9%.
  • Kalita Wave 185 (steel): Average EY was 20.2%, SDev of 0.87, min. to max. EY span of 2.4%.
  • Westmark 6-Cup (plastic): Average EY was 20.5%, SDev of 0.76, min. to max. EY span of 2.7%.
  • Hario, plastic V60 02, with Chemex paper: Average EY was 18.4%, SDev of 1.63, min. to max. EY span of 5.6%.

I had run out of Japanese V60 02 papers, hence the use of the Chemex papers. The results with the V60 02 were significantly different to the other three (p=0.000). There was no significant difference between the Bonavita, Kalita Wave 185 & Westmark (p=0.477). These three brewers combined (n=30) had an average EY of 20.4%, SDev of 0.75 & a min. to max. EY span of 2.7%.

The Hario V60 02/Chemex paper combination was the only brewer to drop below 18%EY extraction (4 of 10 brews, readings of 16.3%, 17.1%, 17.5% & 17.5%EY respectively). Highest EY for the Hario was 22%. The other brewers never dropped below 19.3%, nor exceeded 22%EY.

Maybe a finer grind would have brought the Hario into range, the average EY was certainly lower than the others?  Maybe the thicker, more porous paper allowed more of a bypass effect? Oh well, looks like I’ll be buying the V60 02 papers after all, to see if the difference follows the brewer, or the paper…


CBI Style Drip Brews in the Bonavita immersion cone, additional…

I expanded the brew method over 10 brews, no changes other than using a different single origin coffee for each brew. Each brew recorded was the first brew with that coffee, no dialling in of any sort…

Brew Method Consistency Bonavita CBI style drip

I then thought I’d compare those 10 drip brews with 10 French press brews. Again, the same grinder, grind setting & method for all the French press brews.  No changes between the French press brews beyond using 10 different single origin coffees, one for each brew. Note: I did not use the same 10 coffees in both brewers, so it’s not an absolute like-for-like comparison (plus there are couple of other aspects that can skew results between these scenarios), nevertheless, I found this interesting…


Brew Method Consistency French press.jpg


CBI Style Drip Extractions With Bonavita Immersion Brewer.

CBI style Bonavita drip chart

I have been very much enjoying drip brews made in the Bonavita immersion cone of late. It strikes me that hand pouring for drip can bring with it some inherent inconsistency, even if you’re very regimented, so the Bonavita can maybe help there (especially if you don’t want to be bothered with being very regimented), by using the shut-off valve feature?

Hand pouring, in pulses and/or spirals, can then be replaced by dumping all the boiling brew water, in one quick pour, into the brewer then open the valve. No gooseneck pouring kettle is required. Adding the brew water like this seems a bit counter-intuitive today, but it was previously used by the Coffee Brewing Institute (CBI) back in the 60’s. Back then, Wilbur Curtis made “Gold Cup” manual drip brewers that contained the coffee dose in a compartment, that prevented the grounds from completely mixing with the brew water. The long pre-wet in the method below seems to help even things out & replaces the grounds compartment idea, as the water-logged grounds should sink very quickly to the bed.

If you’re enjoying super consistent, hand poured, drip brews then there’s probably little point in reading further.

1. Boil the preheat water, grind your dose. Add preheat water to Bonavita (valve shut) & filter paper.

2. Make sure the brew water kettle is empty, shake out any drips, then weigh your brew water into the kettle. If you are making smaller brews, then a compact/travel kettle might be best for brew water (I have been using 244g of brew water in the Sage compact, just about the “Minimum” line on the kettle). Don’t destroy your kitchen kettle by trying to boil less than the minimum water volume. I have been using my main kitchen kettle for preheating & rinsing, then the smaller, compact kettle, for brew water.

 3. Drain the preheat water from the Bonavita brewer (a couple of taps to shake out any residual water), start the brew water boiling & weigh out the ground coffee dose.

 4. Shut the Bonavita valve, add dose (13.5g in my case), start timer & bloom with 1.5 times dose weight in boiling brew water weight. Stir to make sure dose is well wetted (carefully, so as not to tear the paper filter). Put the brew water kettle back on the hob/power supply.

 5. At ~1:15 (with my kettle, tune timings for 1:30 fill) re-boil the brew water & at 1:30 quickly dump the remainder of boiling brew water into the Bonavita (taking care not to splash it around if making larger brews), shaking out any drips, 1 quick stir of the surface & open the Bonavita valve at 1:45.

6. Note the time at which you see the water drain from the bed, then give the brewer a couple of taps & leave another 30 seconds, or so, for drips to drain. I have been seeing a dry bed around 3:05 (+/-15 seconds) for quantities above.

So far, my brews are landing +/-1%EY (VST Coffee Tools, drip mode), 5 different coffees, light to medium dark, from 3 different roasters, no change in grind setting (1+10 on a Feldgrind).
CBI style Bonavita drip data
I wouldn’t suggest buying a Bonavita immersion cone, just for this purpose, but it might be worth a try, if you already have one.

EDIT #1 – Different kettles will have different outputs (due to different dimensions & rates of evaporation), given the same weight of brew water added. Adjust your initial brew water weight based on the final output of the brewer. For instance, here I am aiming for 232g of total brew water in the brewer & a beverage 15x the dose weight, or 203g from 13.5g.

EDIT #2 – Whilst the shut-off valve on the Bonavita gives a little more control in stopping your bloom water from dripping through to the cup, or nailing a given output from the brewer, I am finding I still get pretty good consistency using this same basic method with straightforward pourover cones (Melitta style, Kalita Wave).