French Press Crust and Bloom
I've been following some of the very informative discussions here on different French press brew techniques, especially the brew methods link http://www.brewmethods.com/. My question is about the 'crust' that forms, or should form, after initially saturating and agitating the grounds with water. I seem to get a nice bloom forming but not as many of the grounds are floating in it and I don't seem to be getting that nice crust that I've seen in some of the instructional videos.
What am I doing wrong? Grounds not coarse enough? Too coarse? Wrong water temp? I haven't invested in a nice grinder yet but my cheapo Capresso does allow me to adjust the grind size.
Thanx.
Joe
Replies to This Discussion
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Permalink Reply by Keith Eckert on
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Bloom can be affected by multiple factors.
The bloom is caused by the near immediate release of gasses (the bulk of which is CO2) produced during the roasting process when the ground coffee is immersed in brew temperature water. I don't know what coffee you are using, but the bean's natural degassing process starts immediately after roasting and continues for a few weeks after roast. The bulk of the trapped gasses are going to be lost faster in the first week after roast, dependent on packaging (and on storage temperature, humidity, bean density, roast degree and bean size...to name a few). My first guess is that the coffee you are using is likely older than this.
Grinding coffee immediately increases the surface area to volume ratio allowing for in increase rate of gas loss, so amount of time post grind has a big impact on bloom.
Lastly, other factors that contribute to bloom. Some coffee origins are known to have more out-gassing than others. Roast degree has a big impact on bloom. Super dark, oily, Italian roasts have much less out-gassing than the same coffee roasted Full City...at least this is my observation.
Keith
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Permalink Reply by Johnny Steverson on
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Keith,
Super interesting response. I realize the gassing is mainly c02; do you know what those other gases are? -Which ones disperse more quickly? At what point after grinding is the coffee a lost cause? (I've always been told about 15 minutes)
And just to really get into this... would you say it's a slow, steady release of gas, or the first week it loses 50%, second 25%, and after that it's just a waste?
Any thoughts about a dark roast vs. light roast? I guess at a certain point of roasting, you begin forcing out gases already? It would almost seem to me as if the darker the roast, the more bloom that would be possible (assuming freshness).
And lastly, why is the "de-gassing" so important (other than smell)? Do those gases "infuse" with the water That much? Or is it simply aroma?
-PS: I do love awesome blooms, I'm really just trying to dig in and explore all these things I don't really know that much about!
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While I have never seen a scientific published study on degassing rates (I am sure they exist), from my experience I would assume it would look something like this (where X is days):
Again, this is just an anecdotal graph based on observations and likely shifted more to the left.
As for gas production dependent on roast degree, my observations are that gas production increases from light to dark. However, I think that in dark-dark roasts (past the finish of second crack) the woody bean structure is so brittle and fractured that initial degassing is much faster so it seems they bloom less. This is my current theory. Anyone have any expanded thoughts on this?
As with Bloom size and taste, I would venture to say that this is more of a correlation than a causation (like crema production and the quality of an espresso pull). Fresh coffee blooms more, because it is fresh. Many of the volatile oils and aromas that makes specialty coffee so dramatically different also diminish over time through evaporation and oxidation. I would venture to say that a lack of bloom is not the cause of bad coffee, but a sign the coffee is too old.
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Permalink Reply by Joe D'Onofrio on
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Update, I was using a peaberry coffee at the time of this post but have moved on to a certified organic from Nicaragua which has produced a much fuller crust with grounds floating in it and a nice bloom. So maybe the size of the coffee beans has something to do with it as well. I will keep experimenting!
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Permalink Reply by Dennis McQuoid on
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I've noticed lighter roasts tend to create less bloom. Most grinds just sink.
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Permalink Reply by Brady on
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Wow, not sure how I missed this discussion.
A big bloom is simply a sign of very fresh coffee. The outgassing itself is not a good thing - it actually interferes with the extraction process. This is why some of the instructions have you agitate at some point in the process. This is also why there's a prewet or bloom step in drip methods.
Will see if I can find some more on this.
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Permalink Reply by Daniel Demers on
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True - but I have most definitely noticed differences in bloom amount between different coffees with the same roast date. I agree with Dennis's comment above that lighter roasts seem to have less bloom in general, but I would love to know more about why some coffees bloom more/less than others...
Brady said:Wow, not sure how I missed this discussion.
A big bloom is simply a sign of very fresh coffee. The outgassing itself is not a good thing - it actually interferes with the extraction process. This is why some of the instructions have you agitate at some point in the process. This is also why there's a prewet or bloom step in drip methods.
Will see if I can find some more on this.
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Sorry, typed that last reply a little quickly. I wasn't disagreeing with the observation about different blooms for light vs dark. It seems that the OP might have felt that the production of a huge bloom was an important part of the process and I don't think that's the case.
Looked briefly at Illy and found some more on this. Will post under separate cover.
Daniel Demers said:True - but I have most definitely noticed differences in bloom amount between different coffees with the same roast date. I agree with Dennis's comment above that lighter roasts seem to have less bloom in general, but I would love to know more about why some coffees bloom more/less than others...
Brady said:Wow, not sure how I missed this discussion.
A big bloom is simply a sign of very fresh coffee. The outgassing itself is not a good thing - it actually interferes with the extraction process. This is why some of the instructions have you agitate at some point in the process. This is also why there's a prewet or bloom step in drip methods.
Will see if I can find some more on this.
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This post is right on the money.
Skimmed through Illy for more info, and found lots of support for what you've said here.
CO2 is created in the roast process from a couple of reactions (Maillard and pyrolysis). CO2 levels increase within the bean pretty dramatically at middle to later roasting stages. This level starts to increase at first crack and has increased (roughly linearly) by a factor of 6 by second crack. They also confirmed Keith's statement below regarding the reduced ability of the bean to retain this CO2 in darker roasts. So it would seem that your biggest bloom in coffee would come from more darkly-roasted coffees (425 F, full city to use rough terms). Darker roasts had a little more right after roasting but lost it quickly, while the lightest roasts just didn't have nearly as much to begin with.
A little more on the degas rate (by which we mean how quickly the CO2 in the bean dissipates while in storage, not refering to any part of the brew process here). I found a good graph which shows a fairly linear dropoff of CO2 concentration in whole bean coffee down to about half its initial stabilized level by day 20 and 1/4 by day 40. This doesn't seem to speak to the initial day or two post-roast though... which I suspect are far more dramatic.
Hope that helps.
Keith Eckert said:
While I have never seen a scientific published study on degassing rates (I am sure they exist), from my experience I would assume it would look something like this (where X is days):
As for gas production dependent on roast degree, my observations are that gas production increases from light to dark. However, I think that in dark-dark roasts (past the finish of second crack) the woody bean structure is so brittle and fractured that initial degassing is much faster so it seems they bloom less. This is my current theory. Anyone have any expanded thoughts on this?
As with Bloom size and taste, I would venture to say that this is more of a correlation than a causation (like crema production and the quality of an espresso pull). Fresh coffee blooms more, because it is fresh. Many of the volatile oils and aromas that makes specialty coffee so dramatically different also diminish over time through evaporation and oxidation. I would venture to say that a lack of bloom is not the cause of bad coffee, but a sign the coffee is too old.
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Oops, small mistake above. I'd meant to say this:
"So it would seem that your biggest bloom in coffee would come from medium roasted coffees (425 F, full city to use rough terms)."
I know anything that even thinks about 2nd crack is considered dark in some circles, but for many this is still considered a more medium roast.
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Daniel, bean density makes a difference as well. Comparing blooms of higher elevation coffee to lower elevation coffee of the same variety and roast level, the lower elevation coffee is less dense and blooms more. I've tested this using a very unscientific method - chewing the beans to test density;-).
Daniel Demers said:True - but I have most definitely noticed differences in bloom amount between different coffees with the same roast date. I agree with Dennis's comment above that lighter roasts seem to have less bloom in general, but I would love to know more about why some coffees bloom more/less than others...
Brady said:Wow, not sure how I missed this discussion.
A big bloom is simply a sign of very fresh coffee. The outgassing itself is not a good thing - it actually interferes with the extraction process. This is why some of the instructions have you agitate at some point in the process. This is also why there's a prewet or bloom step in drip methods.
Will see if I can find some more on this.
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Well, I've learned a lot already- that blooming is actually a bit of a hindrance to the brewing of coffee.. Can anyone elaborate on why the degas is bad? -It's releasing air so water cannot penetrate at the same time? And, if I am using a pourover method, that I let bloom for a good amount of time, why would I need to agitate further?
Lastly, while the bloom is not a sign of good coffee; a good bloom in relation to a particular coffee would indicate the coffee is better [fresher], right? Because there is a correlation between freshness and aroma and flavor.
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