# Sieving, grind size & immersion brews



## MWJB (Feb 28, 2012)

I have been sieving out the boulders in my Sowden immersions and have noticed something. When much less than 80% of the grind passes through the sieve that I use, I get underextracted brews. If 80% or a little over pass through the sieve, the brew comes in on target.

So, I'm dialling back the grind so that I can pass 80% with the typical coffees I use, then maybe watch the time if in danger of pushing the extraction.

You could also determine a desired % for a given sieve, then do quick test grind & adjust the grinder so that each coffee passes a similar, known good, percentage through that sieve, before grinding proper?


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## jlarkin (Apr 26, 2015)

Interesting! I think I noticed Matt Perger mention that and using a certain size sieve? I've seen so much variation in the size of the holes in a sieve that I wasn't quite sure where to start...


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## MWJB (Feb 28, 2012)

Well, I tried a few cheap kitchen sieves & settled on one that worked with my grinder...& didn't make too much mess in the office kitchen (sieve into a large mixing bowl, then jam funnel into the pot). Originally, I was typically a couple of marks finer on setting & brew extracted well, but I wasn't happy with the, albeit small, amount of dust in the cup. Going much coarser would eliminate this & improve clarity, but clamp extraction, so going just a little coarser, then sifting out the boulders (so as not to affect extraction) was the next logical step.

The sieve size will depend on your typical grind size, obviously if everything passes through the sieve, then the sieve is too big. I'm aiming to lose the 15-20% of the larger grinds. An accurate seive in the 400-600-700-850um region will help you identify your average grind size, but they're very expensive. If you're doing a quick test of grind size, anything that will help you establish a datum (e.g. holds something back) will do. Try what you have to hand & see how it correlates to a brew method.

The thing is, at the same settings, different coffees will grind coarser/finer, this can help you compensate & dial in grind, or give you a heads up on what is going on.

Matt Perger mentioned using 0.45mm(450microns) & 0.5mm(500microns) for espresso...probably work for coarser grinds too, but then you're losing a considerable proportion of what you're grinding. Sieving has been used for decades to identify grinds, Perger seem to have recently done a full 180 on what to sieve out (used to be the smaller particles, which you definitely need in immersions as long as you can keep them out of the cup). Randy Pope from Bunn did an interesting experiment a few years ago where he sieved out both boulders & fines.


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## urbanbumpkin (Jan 30, 2013)

Yes Spence was on about that.....I believe Mr P has now concluded that it's the fines that make espresso.


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## MWJB (Feb 28, 2012)

urbanbumpkin said:


> Yes Spence was on about that.....I believe Mr P has now concluded that it's the fines that make espresso.


...and immersion brews, the biggest problem there is keeping them out of the cup (if unfiltered), so you want to keep them tolerable but not remove them.


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## garydyke1 (Mar 9, 2011)

Is it the comparative boulders which actually provide (in some obscure way) resistance for espresso?

The VTA-6 with 'espresso' burrs produces a grind quality akin to flour to the touch one notch away from burrs touching & yet shots literally gush through with fresh coffee if you don't updose slightly.

The EK43 with coffee burrs one mm away from absolute zero produces a grind which feels more granular and less uniform and you can almost choke a machine completely .


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## MWJB (Feb 28, 2012)

garydyke1 said:


> Is it the comparative boulders which actually provide (in some obscure way) resistance for espresso? .


That's what Perger says on his blog, it may not just be the larger particles slowing the flow, but the interlocking of various size particles (my pocket science input).

All big, or all small, maybe just as likely to gush?

But is gushing a bad thing (fast flow, rather than obvious channelling)? is choking, or getting close to, a good thing? Higher EYs (due to uniformity) need more water, longer shots (in weight) can take less time. Is trying to slow the shot too much (overdosing/nutating, rather than longer preinfusion) not likely to be counterproductive? (...I don't know, just thinking out loud).


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## garydyke1 (Mar 9, 2011)

Possibly not. Fast gushers have less contact time and result in a hotter beverage in the cup. Lower TDS . Then we reduce flow, temp and pressure. Not enough time , too many questions


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## Mrboots2u (May 10, 2013)

MWJB said:


> That's what Perger says on his blog, it may not just be the larger particles slowing the flow, but the interlocking of various size particles (my pocket science input).
> 
> All big, or all small, maybe just as likely to gush?
> 
> But is gushing a bad thing (fast flow, rather than obvious channelling)? is choking, or getting close to, a good thing? Higher EYs (due to uniformity) need more water, longer shots (in weight) can take less time. Is trying to slow the shot too much (overdosing/nutating, rather than longer preinfusion) not likely to be counterproductive? (...I don't know, just thinking out loud).


We need another chart....


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## Mrboots2u (May 10, 2013)

garydyke1 said:


> Possibly not. Fast gushers have less contact time and result in a hotter beverage in the cup. Lower TDS . Then we reduce flow, temp and pressure. Not enough time , too many questions


Ive had 20-22 seconds shots that are 8.9-9 tds

Depends on your definition of gusher


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## MWJB (Feb 28, 2012)

Mrboots2u said:


> We need another chart....


Oh...I have other charts....I could paper the walls with charts....in fact I think I will......MWAHAHAHAHAAA!

Need more data!


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## Mrboots2u (May 10, 2013)

MWJB said:


> Oh...I have other charts....I could paper the walls with charts....in fact I think I will......MWAHAHAHAHAAA!
> 
> Need more data!


Working on it...


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## garydyke1 (Mar 9, 2011)

Mrboots2u said:


> Ive had 20-22 seconds shots that are 8.9-9 tds
> 
> Depends on your definition of gusher


But I bet higher TDS would be possible with longer contact time for the same bev yield .

Think fast shot isn't the same as gusher per say


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## Mrboots2u (May 10, 2013)

garydyke1 said:


> But I bet higher TDS would be possible with longer contact time for the same bev yield .
> 
> Think fast shot isn't the same as gusher per say


Depends if a higher tds is desirable in the first place


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## MWJB (Feb 28, 2012)

garydyke1 said:


> Possibly not. Fast gushers have less contact time and result in a hotter beverage in the cup. Lower TDS . Then we reduce flow, temp and pressure.


Or 'normalise' flow & pressure & add/extend preinfusion to restore the ideal/necessary contact time? What if contact time I the target flow & pressure the means rather than the end?


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## Mrboots2u (May 10, 2013)

MWJB said:


> Or 'normalise' flow & pressure & add/extend preinfusion to restore the ideal/necessary contact time? What if contact time I the target flow & pressure the means rather than the end?


Give me an example please


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## garydyke1 (Mar 9, 2011)

Mrboots2u said:


> Depends if a higher tds is desirable in the first place


I guess if youre at 24% already probably not


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## garydyke1 (Mar 9, 2011)

Flow rate and relationship to pressure is an annoying one when different machines / pumps are in use.

Maxwell mentions the SR Opera runs 190g water in 30 sec at 6BAR. On the Slayer 190g is achieved at a pump setting which is 4 BAR SCACE'd and the results aren't great. Ill put it back to 6BAR and rerun water output tests, I'm pretty sure its less than 190g!


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## Mrboots2u (May 10, 2013)

garydyke1 said:


> I guess if youre at 24% already probably not


I think my preference is less than 10 though ( well that's what Mark tells me







)


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## Mrboots2u (May 10, 2013)

garydyke1 said:


> Flow rate and relationship to pressure is an annoying one when different machines / pumps are in use.
> 
> Maxwell mentions the SR Opera runs 190g water in 30 sec at 6BAR. On the Slayer 190g is achieved at a pump setting which is 4 BAR SCACE'd and the results aren't great. Ill put it back to 6BAR and rerun water output tests, I'm pretty sure its less than 190g!


Is he running an Opera now ?


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## garydyke1 (Mar 9, 2011)

going from a tweet where he mentions one


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## Xpenno (Nov 12, 2012)

I am led to believe that there is a paper being published on this topic. I did speak to Matt about it and the current thought process is that boulders should be removed, fines should stay. Fines = a very high percentage surface area of every dose and are responsible for the majority of the extraction in a given brew. I wasn't allowed to take pics of the graphs and info I was shown (hopefully it will be released soon) but it was very interesting. There was also some info about how boulder extract vs how fines extract, again the thinking is currently that fines extract to a much higher percentage than boulders and there are so many more of them therefore most extraction comes from fines.

Anyway, I've probably not do the info much justice and it's probably not that relevant to the OP but I've just got home from work and need some sleeeps.... zzzzzzzz


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## Xpenno (Nov 12, 2012)

Mrboots2u said:


> Is he running an Opera now ?


That's what he's doing he pressure stuff on and didn't he sell/advertise a three group strada on twitter recently...


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## MWJB (Feb 28, 2012)

Mrboots2u said:


> Give me an example please


20g:48g in 30s @ 9BAR longer preinfusion, faster running shot

20g:48g in 30s @ 5.5BAR less preinfusion, slightly slower running shot.


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## Mrboots2u (May 10, 2013)

MWJB said:


> 20g:48g in 30s @ 9BAR longer preinfusion, faster running shot
> 
> 20g:48g in 30s @ 5.5BAR less preinfusion, slightly slower running shot.


Same grind ?


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## MWJB (Feb 28, 2012)

garydyke1 said:


> Flow rate and relationship to pressure is an annoying one when different machines / pumps are in use.
> 
> Maxwell mentions the SR Opera runs 190g water in 30 sec at 6BAR. On the Slayer 190g is achieved at a pump setting which is 4 BAR SCACE'd and the results aren't great. Ill put it back to 6BAR and rerun water output tests, I'm pretty sure its less than 190g!


Flow rate is an annoying one because there are so many to choose from: flow to group no PF, flow from PF over total shot time, flow from PF over observed flow (the last 2 don't seem to be indicative of anything other than how big your drink is).


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## MWJB (Feb 28, 2012)

Xpenno said:


> Fines = a very high percentage surface area of every dose and are responsible for the majority of the extraction in a given brew. I wasn't allowed to take pics of the graphs and info I was shown (hopefully it will be released soon) but it was very interesting. There was also some info about how boulder extract vs how fines extract, again the thinking is currently that fines extract to a much higher percentage than boulders and there are so many more of them therefore most extraction comes from fines.


I don't get the fascination with "surface area" in percolation brews. Fines will extract more because they have less volume (related to surface area sure), boulders will extract less evenly because the surface will be more over-extracted, the core under-extracted (same for immersions). No matter how much surface area you have, you can't extract 20+% of the mass from surface area alone, you have to be talking volume. Increased surface area is just the gateway to accessing the volume?


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## MWJB (Feb 28, 2012)

Mrboots2u said:


> Same grind ?


Grind would be the one that allowed both to hit a similar EY, so possibly not...quite likely not.


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## Mrboots2u (May 10, 2013)

MWJB said:


> Grind would be the one that allowed both to hit a similar EY, so possibly not...quite likely not.


So then is it pre infusion and pressure or grind thats the driver ...


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## Xpenno (Nov 12, 2012)

MWJB said:


> I don't get the fascination with "surface area" in percolation brews. Fines will extract more because they have less volume (related to surface area sure), boulders will extract less evenly because the surface will be more over-extracted, the core under-extracted (same for immersions). No matter how much surface area you have, you can't extract 20+% of the mass from surface area alone, you have to be talking volume. Increased surface area is just the gateway to accessing the volume?


Agreed but the figures they were talking about were interesting. Hopefully the paper will be published in the not too distant future.


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## MWJB (Feb 28, 2012)

Mrboots2u said:


> So then is it pre infusion and pressure or grind thats the driver ...


I don't think any one is a magic bullet, they interact to hold coffee & water together long enough, at a given brew ratio, to extract ideally?


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## AndyS (May 12, 2012)

Xpenno said:


> Fines = a very high percentage surface area of every dose and are responsible for the majority of the extraction in a given brew. I wasn't allowed to take pics of the graphs and info I was shown (hopefully it will be released soon) but it was very interesting. There was also some info about how boulder extract vs how fines extract, again the thinking is currently that fines extract to a much higher percentage than boulders and there are so many more of them therefore most extraction comes from fines.


Don't really believe this since fines make up a relatively low percentage of the ground mass. If we generously suppose (based on looking at typical graphs) that (1) fines are 25% and coarse particles are 75% of the total mass, and (2) assume the fines extract to the theoretical 30% maximum, then we've still only extracted 7.5% of the original coffee. This means that around 12.5% to 15.5% of the extract has to come from the boulders in order to get a typical balanced brew.


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## Colio07 (Mar 9, 2015)

Xpenno said:


> That's what he's doing he pressure stuff on and didn't he sell/advertise a three group strada on twitter recently...


Think Maxwell's got some sort of sponsorship deal for the Opera - he appeared in an ad for it in Caffeine (or perhaps the London Coffee Festival brochure - can't remember which).


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## jlarkin (Apr 26, 2015)

Colio07 said:


> Think Maxwell's got some sort of sponsorship deal for the Opera - he appeared in an ad for it in Caffeine (or perhaps the London Coffee Festival brochure - can't remember which).


You're practically right on both fronts, it's in the episode of caffeine that was given on entry @ LCF .


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## fatboyslim (Sep 29, 2011)

Awhile since this was updated. I'm looking to purchase a sieve to remove fines from my filter grind.

I read in Scott Rao's book that anything smaller than 50um (micron) he considers to be fines.

Is this other people's understanding? The Hausgrind I use for brewed does produce some powdery bits on coarse grinds but not too many.

Just want to see what effect, if any, just extracting the larger particles has in the cup.

So far I'm looking at a 50 micron zooplankton sieve off eBay. Any other recommendations?

Budget for this is pretty low so I wouldn't consider the Sigma-Aldrich test sieves at £104 each!

http://www.ebay.co.uk/itm/50-MICRON-ZOOPLANKTON-STACKABLE-SIEVE-/221850135174


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## MWJB (Feb 28, 2012)

For drip brewed coffee, 'less than ideal' particle sizes are traditionally considered to be in the region of

Randy Pope's sieving experiment at the NBC targeted grinds of ~850um to ~1200um

Folks have used 250um to remove fines, but notably Perger (who also did this) is now saying sieve out the larger particles instead, leave the smaller particles in.

Never tried very fine mesh sieves (


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## fatboyslim (Sep 29, 2011)

MWJB said:


> For drip brewed coffee, 'less than ideal' particle sizes are traditionally considered to be in the region of
> 
> Randy Pope's sieving experiment at the NBC targeted grinds of ~850um to ~1200um
> 
> ...


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## jlarkin (Apr 26, 2015)

@fatboyslim don't bother with the zoo plankton sieve. As I'm a nice guy I'll whisper you a secret (I've not admitted this to anybody else on here up until now). I bought a few and didn't manage to get anything sieved out even with the slightly larger ones, I think as MWJB said it stuck to the sieve or itself. I'll give it another go later on or tomorrow just in case I missed something and it works this time (tried once, it seemed such an abject failure that I left it after that).


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## MWJB (Feb 28, 2012)

No, I've only sieved out larger particles. This has made brews more even tasting. Latest thinking is that the fines may not be as damaging as previously thought.

European Coffee Brewing Centre drip grind is around 600um median grind size, only the smallest 20% (though in reality what lands in the pan can be larger % than this), or so, are ideally supposed to be under 400um. A 4 sieve protocol used to be typical, sieves arranged as factors of 1.41, so if 425um is your lower cut-off, next sieve would be ~600, then ~850 and ~1200 as the upper cut-off (or just a tiny % by weight).


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## fatboyslim (Sep 29, 2011)

MWJB said:


> No, I've only sieved out larger particles. This has made brews more even tasting. Latest thinking is that the fines may not be as damaging as previously thought.
> 
> European Coffee Brewing Centre drip grind is around 600um median grind size, only the smallest 20% (though in reality what lands in the pan can be larger % than this), or so, are ideally supposed to be under 400um. A 4 sieve protocol used to be typical, sieves arranged as factors of 1.41, so if 425um is your lower cut-off, next sieve would be ~600, then ~850 and ~1200 as the upper cut-off (or just a tiny % by weight).


But there is no arguing that a big filter grinder like a Mahlkonig Tanzania produces a very even grind with a very small amount of fines, and also that this grinder produces sensational brews! If fines are around 50um and a 50um sieve struggles to remove them, then maybe something like a 125um sieve might have a better chance of removing these fines without touching anything in the ideal grind range for drip grind. Don't think the Hausgrind ever really produces boulders that are substantially larger than the average (think my Preciso is more prone to that), so not too worried about the larger particles.


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## robashton (May 9, 2015)

Well, the EK43 creates more fines... (apparently)


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## MWJB (Feb 28, 2012)

I think there is a slight difference between "fines" and "smaller than ideal particles", if I remember right, Scott Rao suggested that at

As you can see here, the modal peak for the Tanzania starts between 300-400um, median will be a little to the left of the apex (mode - most common particlesize, a shade over 600um).


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## MWJB (Feb 28, 2012)

robashton said:


> Well, the EK43 creates more fines... (apparently)


Yes, but keeps the incidence of larger boulders down, meaning a narrower distribution.


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## fatboyslim (Sep 29, 2011)

MWJB said:


> I think there is a slight difference between "fines" and "smaller than ideal particles", if I remember right, Scott Rao suggested that at
> 
> As you can see here, the modal peak for the Tanzania starts between 300-400um, median will be a little to the left of the apex (mode - most common particlesize, a shade over 600um).


I like that graph a lot! Thanks for that. So if I wanted to try to mimic that grind distribution curve in the smaller size range, anything less than


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