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"Japanese" Iced Coffee: Grind Finer?
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Sam21
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Joined: 20 Sep 2011
Posts: 409
Location: Northwest, CT
Expertise: I love coffee

Grinder: Baratza Virtuoso, LIDO,...
Vac Pot: Siphon, Aeropress, CCD
Drip: Kalita Wave, Beehouse,...
Roaster: Hottop KN-8828B-2K
Posted Sat Jun 1, 2013, 10:43am
Subject: "Japanese" Iced Coffee: Grind Finer?
 

Hi all,

I've never brewed iced coffee in this manner and would like to try. I have one question about the grind. With typical pourover brewing, if I increase the ratio by addin more coffee a slightly coarser grind will be needed to compensate and achieve a similar extraction. Similarly, if less coffee is used a finer grind will be needed to achieve a similar extraction. The difference is in the final strength. I use my pouring, within reason, to hit my brew time and always aim for around 3min.

Please let me know if I'm on the right track there regardin changing grind for dose.

Now for iced pourover coffee. Because I am pouring less water through the same amount of coffee, I assume I would need a finer grind to achieve a good extraction. The ice would then dilute the strength. Correct?

Just looking for some overall confirmation.

Thanks!
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dzollman
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Joined: 2 Jun 2013
Posts: 4
Location: Philadelphia, PA
Expertise: I live coffee

Posted Sun Jun 2, 2013, 9:36am
Subject: Re: "Japanese" Iced Coffee: Grind Finer?
 

I was actually just about to post a similar question. Here are my thoughts--I'm not an expert, so note that some of my assumptions could be wrong. And I apologize in advance for a long post that doesn't answer your question.

Since I just make coffee for myself, I only want to brew one cup at a time, as opposed to going up to larger amounts (e.g. Chemex), which would probably be much easier for iced coffee.

In the past, I've made iced coffee with a normal pourover grind, with the following approach for an 8oz cup. (This just my own uninformed, imprecise approach--haven't done much research on it.)
  1. Grind: normal grind for hot pourover cup
  2. Amount of coffee: somewhere between the amount I'd normally use for an 8oz cup, and the amount needed for a 12oz cup
  3. Water: 4oz
  4. Brew: brew 4oz of coffee over a receptacle. Move the filter cone over to my ice-filled mug. Pour the 4oz of coffee through the cone AGAIN so that I'm (theoretically?) getting the extraction I'd normally get with 8oz of water.

I initially found that I needed a lot of ice to cool down the coffee, which resulted in too much dilution, so that's why I started to increase the amount of coffee in step #2.

There are a couple problems with this:
  • The double-brewing approach requires extra equipment and it's a pain in the neck to maneuver all the pieces.
  • There's probably a lot of heat loss between the two pours.
  • It's harder to hit the target extraction time of 2:30 to 3:00, and I don't know if the gap in between pours interferes with the extraction. (You've also got that time at the end of the first pour when coffee is still dripping, but not all the grounds are in contact with water.)
  • In the second pour, where I'm trying to complete the extraction, I don't know if the partly-brewed water affects the chemistry of the extraction.


So it would be nice if I could find a way to make iced coffee in a single pour. That means attempting a full extraction with only 4oz of water.

That let me to my question (similar to yours): if I used a finer grind to slow down the drip, could I hit 2:30, thereby getting a full extraction, before 4oz of water have filtered through?

This idea relies on a couple assumptions about the chemistry of extraction, and I'm not sure if these are correct:

Assumption #1: using a finer grind does not change the optimal extraction time of 2:30 to 3:00.
Assumption #2: using a finer grind doesn't change any other qualities of the extraction, as long as the timing is correct.
Assumption #3: as long as the extraction time is long enough, it is possible to get a full extraction with half the water (in other words, there's no saturation- or equilibrium-like effect that would hinder a full extraction).

The other problem here is that the fine grind could clog the filter, depending on how fine you have to go in order to do this successfully.

I was wondering if anyone would have insight into those 3 issues.
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Sam21
Senior Member


Joined: 20 Sep 2011
Posts: 409
Location: Northwest, CT
Expertise: I love coffee

Grinder: Baratza Virtuoso, LIDO,...
Vac Pot: Siphon, Aeropress, CCD
Drip: Kalita Wave, Beehouse,...
Roaster: Hottop KN-8828B-2K
Posted Sun Jun 2, 2013, 10:20am
Subject: Re: "Japanese" Iced Coffee: Grind Finer?
 

I can easily drag a 150ml pour out to 3min including my bloom, so timing is not much of an issue. It's more so what to do with the grind - i really do not know much about extraction when it comes to changing the dose. Within a range, taking other variables into consideration, ratios are scalable but I don't know much about the impact of changing the ratio when you start adding more grams of coffee or using less water.

I'll be doing plenty of my own experimenting. Currently, I'm using my Beehouse and my typical ratio. 18g/300ml. I go with 150ml of water over the 18-20g of coffee over 150g of ice. I keep my brew time at 3min which is my normal time. It's when I get to the grind that I'm just not sure. I can easily hit 3min wih my normal grind and just a very slow and steady pour - great kettle. My question is all about extraction.

Same goes for if I was to brew it in an aeropress. 150ml of water, 18g in the aeropress, 150g of ice. Do I have to go finer with the grind to properly extract that much coffee with half te water? Then that super strong coffee would be diluted by the ice.
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dzollman
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Joined: 2 Jun 2013
Posts: 4
Location: Philadelphia, PA
Expertise: I live coffee

Posted Sun Jun 2, 2013, 11:53am
Subject: Re: "Japanese" Iced Coffee: Grind Finer?
 

Hmm, I see what you're saying. So the question is, with the same timing and grind size, is there any consequence to either (a) the reduced water volume, or (b) the reduced rate of flow?

This is all speculation, but one possible reason it might affect the extraction is if the pool of water in the cone approaches equilibrium before you've extracted all the desired materials from the coffee grounds. With normal rate of flow, you're quickly adding fresh water and removing brewed water. But as you reduce the rate of flow, the water is "cycling" more slowly, and you'll end up with a higher concentration in the cone. I have no idea whether it's possible to reach equilibrium in this situation, but if it is, then the high concentration in the cone would cause the extraction to slow down (or stop).

If that's the case, then a finer grind would actually make it worse, because you'd reach equilibrium more quickly.

I'm sure there's someone here who could just answer the question straightaway, but I find it interesting to try and work this out in my head.
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Sam21
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Joined: 20 Sep 2011
Posts: 409
Location: Northwest, CT
Expertise: I love coffee

Grinder: Baratza Virtuoso, LIDO,...
Vac Pot: Siphon, Aeropress, CCD
Drip: Kalita Wave, Beehouse,...
Roaster: Hottop KN-8828B-2K
Posted Sun Jun 2, 2013, 12:12pm
Subject: Re: "Japanese" Iced Coffee: Grind Finer?
 

I haven't had any issue with the cone draining. It flows nice and steady and at such a steady introduction of water it's all nice and easy. I could go finer or more coarse without issue.

Still interested in the impact of extraction - obvs keeping the grind the same and using less water would end up underextracted. So I can only assume a finer grind is needed.
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dzollman
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Joined: 2 Jun 2013
Posts: 4
Location: Philadelphia, PA
Expertise: I live coffee

Posted Sun Jun 2, 2013, 12:30pm
Subject: Re: "Japanese" Iced Coffee: Grind Finer?
 

I just assumed that if you're pouring more slowly, it's also draining more slowly. And with a finer grind, even if it's draining at the same rate, the concentration would still increase more quickly due to the increased surface area.

This thread seems to address the original question, but I don't completely understand it. The answer could also be different for drip and immersion techniques. http://coffeegeek.com/forums/coffee/questions/579753
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Sam21
Senior Member


Joined: 20 Sep 2011
Posts: 409
Location: Northwest, CT
Expertise: I love coffee

Grinder: Baratza Virtuoso, LIDO,...
Vac Pot: Siphon, Aeropress, CCD
Drip: Kalita Wave, Beehouse,...
Roaster: Hottop KN-8828B-2K
Posted Sun Jun 2, 2013, 3:25pm
Subject: Re: "Japanese" Iced Coffee: Grind Finer?
 

I gather that because there is less water to extract the "good stuff," which comes in stages during brewing, if you keep the grind the same but lower the amount of water it will underextracted compared to the original ratio. Any increase in the ratio by adding more coffee or less water will decrease the extraction percentage.

It is a but different with pourover brews as you have to take percolation/flow rate into account. There are just more variables.

By that information, here is what I gather. If I am brewing an aeropress at 17g/275ml and decide to use 200ml instead or maybe decide to increase the coffee dose to 21, I am going to extract less compared to the original brew. A finer grind to some extent would be needed to achieve a similar extraction percentage at this higher strength. Taste obviously then becomes the biggest factor.

I wonder if that understanding is correct.
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dzollman
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Joined: 2 Jun 2013
Posts: 4
Location: Philadelphia, PA
Expertise: I live coffee

Posted Thu Jun 6, 2013, 4:24pm
Subject: Re: "Japanese" Iced Coffee: Grind Finer?
 

So I made my way through that thread I linked to earlier. Based on that discussion, it sounds like the extraction percentage is not affected by brew ratio. Grind, timing, and all other thing being equal, doubling the brew ratio will roughly double the resulting beverage strength, but the extraction percentage would stay the same.

(However, there are practical implications to changing the brew ratio--it changes elements of how the water flows, the way you pour the water, etc. But time is the main factor, and you're telling me that you're able to control the timing well enough that it isn't a variable.)

I don't know if there are other perspectives/theories that would contradict that.

The idea that "there is less water to extract the good stuff" would imply that there's some kind of limit to the amount of solute the water can hold. Within a reasonable range of brewing ratios, there's no such limit. That might start to change when you get to REALLY high brew ratios resulting in REALLY high beverage strength--you could get to a point where the solution is so concentrated that it's at "equilibrium" and it cannot continue to extract. However, I don't think doubling the brew ratio is enough to each that point.

That's where my head is right now...I'm open to being challenged.
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Sam21
Senior Member


Joined: 20 Sep 2011
Posts: 409
Location: Northwest, CT
Expertise: I love coffee

Grinder: Baratza Virtuoso, LIDO,...
Vac Pot: Siphon, Aeropress, CCD
Drip: Kalita Wave, Beehouse,...
Roaster: Hottop KN-8828B-2K
Posted Thu Jun 6, 2013, 5:05pm
Subject: Re: "Japanese" Iced Coffee: Grind Finer?
 

Kudos to you for working through it! I do agree about changes to grind for variables of flow rate and the additional need to change the time.

I've been playing with using more and less coffee and checkin the flavor (keeping all else the same). So far, the cups have tastes great, just more concentrated. I never made it through the whole thread.
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