Kruve – what can it tell us?

Kruve Lido 0.5 0.63 0.75

As well as allowing us to ‘top & tail’, or ‘top or tail’ our grind distributions, sieves can also tell us something about our grind distributions.

I decided to dedicate one of my grinders (Lido 1) to optimising via my Kruve, but still allowing for use without sifting, for days when I just didn’t fancy the additional effort. Immediately it was obvious that 400 & 800 size sieves excluded a huge amount of my grind distribution with my Lido 1. Also a grind centred between these sizes was too fine for my regular drip brewing method. Therefore, I fitted the largest size I had (1100) in the top section and a reasonably fine sieve (350) in the lower section. This gave me…

Kruve Lido 0.75 between sieves

At setting 0.50 from marked zero I landed 69% of the ground weight between 350 & 1100 sieves. This suggests my standard deviation for this grinder is less than 1.773, calculated as SQRT(1100/350). As an aside, I found that 400 & 1100 sieves gave me 68% between them and a standard deviation of 1.658 for this grinder, in this range. (SCAA & ECBC drip grind recommendations echo E.E. Lockhart’s 1950’s analysis, aiming for a standard deviation of 1.414, but this does not seem to be absolutely necessary for smaller brews).

Setting 0.63 also landed a healthy 66% between these sizes, with an even balance between sub 350 (16%) & larger than 1100 (18%) particles. Note that there is typically a bias towards the smaller end with most usable grinds, so this shows I am already coarser at 0.63 than will leave me with the average grind setting targeted by these sieves (620 Kruves). This would be an ideal place to stop, however, this was still slightly on the fine side for what I wanted, with my 1-mug V60 brews averaging 21.5%EY without sifting & removing any portion. I would be happier with a 20.5%EY average for a complete grind distribution, though I can exceed this happily when removing the largest 15-20% of ground weight.

Setting 0.75 gave 62% between the 350 & 1100 sieves. This is not a sign that the distribution is getting worse, but simply that I am now so coarse that I won’t fit the distribution within these sizes to +/- one standard deviation. Again, note that the sub 350 particles are now a much lower % than those larger than 1100.

Another way to view these results might be like this, with cumulative & diminishing weights at each interval, for each setting…Kruve Lido 0.75 cumulative & declining fullCool, eh? Kind of ‘X-ey’ 🙂 But probably a little hard to grasp until you blank out the area above 50%…

Kruve lido 0.75 cumulative & declining 50%

This now gives us a more intuitive hump/peak type diagram. The farther left the apex of the trace, the finer the grind. The farther right the apex of the trace, the coarser the grind. The more acute the angle between the cumulative & diminishing traces for the same setting, the tighter the distribution. The more obtuse the angle, the wider the distribution. Look at how the black ‘0.75’ trace almost touches the red 0.63 trace at 350. Blue (0.50) & red (0.63) traces are very similar & virtually parallel between 350 & 1100.

For now, I have settled on setting 0.69 with 500 & 1100 sieves. I get a maximum of ~20% under 500. This allows me to save a little time by being a coarser than I need to remove the bottom 15%, or so, for immersion brews. The 500 is also quicker & easier to clean.

This setting also retains ~20% on top of the 1100, which I discard for drip brews. Kruve have just announced availability of larger sieves, so I intend to replace the 1100 with a 1200, to allow me to sift out either the bottom 15% or the top 15% at will, depending on brew method.

Kruve Lido 0.69 between sieves




Aeropress & Able disc as shower screen for pourover brews.

I have been enjoying my Kalita Wave 185 brews, but not finding them quite as consistent as I might like, also (maybe due to the shallower bed) noticing a little more non-dissolved solids in the cup. Let’s not forget too that I’m actually pretty lazy…finding a method that allowed me to use the same grind setting & pour regime as a single mug V60 brew (see previous posts for V60 recipe) was also a factor. Maybe I should have said that first…?

Years ago I bought a Swissgold KF300 (AKA Frieling ‘Coffee for one’) & whilst useable, it seems to retain water above the shower insert and there’s little space between the insert and the bed. Coffee also tends to find it’s way up the outer walls of the insert. I guess, like many folk, I have  few coffee brewers not actively employed all of the time. So, I thought I’d try using the Aeropress with Able disc in a similar fashion, but suspended above the brewer. Able disc is the ‘fine’ version if it makes a difference, I have also tried a paper Aeropress filter but found it held the water back & results weren’t good enough to encourage me to persevere, without also changing too many other aspects of the recipe.

Grind & weigh coffee dose, add to Kalita Wave 185 placed on mug/cup. Slide cup/mug & Kalita Wave 185 into the brew stand, sitting under the hole. Also place the Aeropress on the scales/brew stand so that when you later place it over the Kalita Wave, it doesn’t throw out your brew water weight after the bloom:


Bloom from your gooseneck kettle as normal, directly onto the bed, then stir/shake the brewer to ensure even wetting. I did initially try blooming through the Aeropress too, but extraction dropped, maybe due to insufficient agitation?


Whilst the bloom is…erm, blooming, place the Aeropress on top of the brew stand, ready for the brew water. At the end of the bloom time pour the brew water so that the stream falls straight down from the kettle spout, ideally landing in the centre of the Able filter.


After adding the last of the brew water give the Kalita Wave 185 & cup/mug a little shake to ensure grounds are washed off of the filter wall, though I am typically seeing far less grounds on the filter wall with this method. Note: I generally brew one single mug at a time with my Kalita Wave 185, using 225g of brew water. You can’t easily see the slurry level in the brewer using this method, so be sure to visually check slurry level between pulses if making large brews that could potentially overflow the brewer!


I feel the cups brewed in this manner have maybe less body than the traditional method, but improved clarity of flavour wins out for me. I am also finding this method more repeatable…but that may say more about me than the Kalita Wave in normal circumstances.

Obviously, if you don’t already own all the equipment mentioned, buying it all to emulate some crank on the internet is probably not the most cost effective route to a tasty cup. A good auto drip brewer can be had for about the same money.

Fines don’t over-extract.

I grow more & more confident of this.

Fines* affect flow rate in percolation. They need to slow the flow enough to extract the bulk of the bed. Too many and flow will be slowed to the point that the bulk of the bed over-extracts and you exceed good tasting solubles yield. Go finer still & they plug the bed, forcing water through paths of lesser resistance (channelling if you will), extraction drops because the whole bed cannot be extracted evenly enough, but the minority of the mass is over-extracted giving a low extraction with predominantly bitter flavours.

In immersion they make their presence felt by actually getting into the brew as undissolved content. Too many and the brew will be bitter, but still at a level of extraction that would otherwise be sweet and balanced if fines were mitigated by grinding a little coarser or sifting out the smallest component.

Fines typically facilitate the over-extraction of larger particles, or lead directly to bittering flavours by coating the tongue, but are likely not responsible for an excess of soluble solids in themselves.

(*…if anyone can actually agree on a definition, that is – E. E. Lockhart suggested the <5% at the fringes of normal distribution, all other definitions I have seen seem somewhat arbitrary, with the exception of the 2nd peak in espresso grinds at ~50µm)




Drip brewing: Brew time & extraction.

For a given brew ratio & brew weights, it is fairly normal to bloom/pre-wet for a specific amount of time, add water at regular intervals, or by a given total time, then aim for reasonable window of time (+/-15 seconds might be reasonable for a number of brews across different coffees) for that brew to end (at perhaps a visible dry bed plus drip time).

However, if your brew time deviates, proportionally, less than your extraction yield (e.g. the same brew time results in inconsistent extractions), you lose a mechanism for controlling the brew. To use brew time to it’s best advantage, your deviation in brew time should perhaps be greater than that of the extraction yield (e.g. a reasonable deviation in brew time still results in consistent extractions).

In my least consistent recipes there seems to be a trend in that the standard deviation (Sdev.) of total brew time has been close to, or less than the standard deviation in extraction yield (calculated as a proportion of each parameter, by dividing the Sdev. by the mean brew time and EY).

If your brew time deviates by around 1.3 times, or more, than that of the EY, this actually seems to make it easier to brew consistently.

Long story short, you may not be able to rely on brew time alone to ensure consistency, without cross referencing against EY.




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 ≤0.80%EY is certainly possible, suggesting the vast majority of brews, across different coffees, landing ±1.81%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.