I used 1-1/3 scoops of beans, inverted, Coava filter, filled the tube up to the top and steeped 1:30 min. I ended up with 4 oz of concentrate which I topped up with 4 oz of water.
He likes it stronger. He used 1-2/3 scoops of beans, inverted, filled the tube up to the top and steeped somewhat longer. He ended up with 2.5 oz of concentrate and he topped up to an 8 oz mug.
He pointed out that he was getting much more bloom than I (which accounted for less to plunge and less concentrate in the cup).
I tasted his and he tasted mine. His was, if anything, weaker, with less aroma and flavor.
We reasoned it out as follows: More coffee steeping = more bloom = less steep-water = less 'character' in the cup. And that leads to an inverse relationship: More coffee = weaker brew. How strange is that?
My son has confirmed that relationship with the last 2 half-lbs of fresh roast I gave him. (...except when he brewed a full pot on his Bunn and overflowed the filter. Messy...)
for what it's worth, I've been finding this an issue with the Coava filter. More coffee grounds ends up mathematically with a higher absorption ratio.
In simple terms, the wet puck weighs more after brewing than it should.
I'm still trying to work out exactly what's happening, but the effect is real and can really mess up measurements of strength and evaporated pucks and evaporated coffee.
Usually not an issue with paper or poly filter felt. However, my absorption ratios exceed 2 (and even 3.0!) with the Coava filter - for some reason, the pucks are much wetter, which means more trapped coffee. This is part of why I started questioning how extraction is measured in the other thread.
I usually have no trouble with paper or poly filter felt up to a brew ratio of 18%, but the Coava filter doesn't like brew ratios much higher than 8-9% for some reason. I think it has something to do with how the metal holes plug up with fines - so you end up with less coffee in the cup to dilute with because they can't be pressed out of the puck.
Some quick calcs: 1 scoop ~ 13.5g Your coffee ~ 18g Son's coffee ~ 22.5g
You added on average about 175g brew water (based on my experience). This would make your brew ratio around 10%.
Your son filled to the top with 22.5g of coffee. In my experience, with normal bloom you may be able to get about 175g of water into the cup, but if minimal bloom maybe 205g of water. If the bloom is really bad, you might be around 145g of water. This makes his brew ratio somewhere between 10% on the max water side to around 15%.
The kicker comes when the absorption ratio gets much higher than about 1.5 (meaning the puck is still saturated with perfectly good coffee). I find that the coffee that's still in the puck is very useful. The absolute minimum I've ever been able to press out of my aeropress is about 1.0, so I think that's the floor level - i.e. the amount of water that's in the cellulose of the grounds and not really "coffee".
It caused me to do a bunch more evap tests on coava presses vs. paper, and I find the missing coffee is stuck. In the puck. In the friggin' puck. Makes me crazy! LOL
Just when ya think ya understand something...
Back to your presses, you SHOULD have produced about 5 1/4 oz of 2.3% strength coffee (not 4oz, meaning more than an ounce of coffee was stuck in the puck).
Your son SHOULD have produced a bit more than 4 oz of 3.8% strength coffee (instead of only 2.5 oz, meaning almost an ounce and a half of coffee was still trapped in the puck).
I know this because I routinely produce 100g of coffee with an 18% brew ratio and 22.5g of coffee. But not with the Coava. With the Coava, I struggle to get much more than 60 or so grams of coffee... along with a very wet puck.
So, the calculations start to really work out if I take the wet puck from the coava press and re-press it (hard) through a paper filter - out comes another 20-30g of perfectly fine tasting (if not slightly cold) hi-strength coffee concentrate. At around 4% strength, it means I'm missing another gram of TDS in the cup - which makes a HUGE difference when dealing with small volumes. In a cup of diluted coffee concentrate, missing 25% of your TDS is a problem.
In fact, I'm in the process of re-vamping my extraction calculator to take into account a higher wet-puck mass (and therefore higher absorption ratio).
Using that thinking, the dilution ratio of your son's brew is probably the culprit, coupled with the inability to obtain enough coffee to dilute to 8 total ounces. Also a case where the AeroPress can be made sensitive to brew ratio (i.e. the brew ratio causes the coava to keep more coffee in the puck and less TDS in the cup). My primary filters are the paper and my 10 micron filter felt.
So far, I'm not impressed with my tenspot expense for the Coava.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
I would buy that except that we both made almost identical cups using the same Coava filter. Mine, with less grinds produced more concentrate.
Before he tipped and plunged, I could see a stratification, what I interpreted as bloom. In mine I did not see quite so much.
There will surely be coffee 'stuck in the puck'. I agree that the puck is less 'squeezable' when using the Coava filter. Arguing against that is that the plunge is much easier with the Coava than with the paper filter. Arguing against that is that an air cushion seems to make the plunge easier.
What I'm saying is that, with excessive grinds, the bloom can persist even after stirring and take up the space which I would normally fill with water for steeping.
And above all is the consideration that my cup tasted much better than his, also a piece of evidence, albeit ...not easily quantified.
I would buy that except that we both made almost identical cups using the same Coava filter. Mine, with less grinds produced more concentrate.
Before he tipped and plunged, I could see a stratification, what I interpreted as bloom. In mine I did not see quite so much.
There will surely be coffee 'stuck in the puck'. I agree that the puck is less 'squeezable' when using the Coava filter. Arguing against that is that the plunge is much easier with the Coava than with the paper filter. Arguing against that is that an air cushion seems to make the plunge easier.
What I'm saying is that, with excessive grinds, the bloom can persist even after stirring and take up the space which I would normally fill with water for steeping.
And above all is the consideration that my cup tasted much better than his, also a piece of evidence, albeit ...not easily quantified.
I don't disagree, Jerry. Some other things to consider:
-Even with an air pocket, I still get excessive absorption ratio with the Coava filter. Last night, I tried to screen/sift out boulders and brew them only, but even that little teeny bit of fines was enough to end up with a slow/high effort press and a heavy puck.
-For some reason, I'm getting a harder plunge with the Coava than paper filter even. This seems to be contrary to your experience.
-Yep, agree on the bloom interfering with how much steep water you can put in. I've had a little luck in pre-wetting the grounds with 15g of cold water and going to as close to 208°F water as I can get. the pre-wetting seems to help calm down the bloom.
-This morning, I did an 18g with 225g water, but the bloom had me trickling the water from 140g to 225g over 30 seconds. So it's hard for me to figure out when the contact time started. Even at 1 1/2 minutes, it was a bit underextracted (I could only fill to about 300g to normal strength by taste, rather than 350g). Paper filter this morning.
-The last thing - the temperature of the brew water. Do you use just off boil or lower temperature? With the sensitivity of the Aeropress to temperature, the higher the brew ratio, the lower the brewing temperature and a corresponding effect in extraction. I think this is because the larger mass of ambient temperature coffee ends up with a lower temperature brewing slurry.
I find that it seems (anecdote alert - only spotty data supports the following hypothesis) the temperature of the slurry drops further when the bloom is more pronounced. Sometimes you can counter this with trickling in hot water as the bloom subsides, but then you need to make a large adjustment in contact time - BUT if you're not starting out with hot enough water, it will quickly drop to below good extraction temperatures in a hurry. Reference: "Temp During Brewing: A Press Pot compared to an Aeropress"
Just some more food (drink) for thought, anyways. I do agree with the bloom interfering with extraction, but I think it's not as straightforward as the bloom being the cause - I think the bloom causes less water to be used which reduces brew temperature, and the higher absorption ratio using the Coava produces less coffee with more grounds, which messes with the assumption of the TDS in the cup.
I'm trying to like the Coava, but I'm just not feeling it. I'm not wild about the fines (bit worse than the 15micron filter felt), and I don't like the sensitivity to finer grinds that the polyester filter felt doesn't seem as bothered by. I do like the cleanup, and it doesn't absorb any water - but it really messes with small volume measurements of extraction because of the absorption. There's a local coffee house that brews any method you want, when you request an Aeropress, they use a Coava with it - but the results aren't even CLOSE to them brewing with a Chemex.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
This morning's coffee was brewed with 19.1g of dry grinds. After plunging/pressing not unusually hard, the wet puck weighed 45.4g. So I had 0.9 oz of residual water in the puck.
There were 2 Coava filters offered originally. The one I have is the earlier model, now discontinued (?) thickness 0.010 inches with 300 micron holes. The later one is thinner with smaller holes. The way I measured the hole diameters was to use a set of low-cost number-drills from China and using the back (unfluted) ends as a gauge and double-checking the drill size with a micrometer.
If you have the thinner one (0.008 inches) you will have a different 'plunging' experience than me. You will observe less particulate in the bottom of your mug (and more plugging the holes).
I just got my Coava, so it must be the smaller holes. I think it sucks, but that's my opinion - at this level, I don't like the fines and I hate the plugging and press effort.
Your data seems like a "normal" press to me. Absorption ratio below 2, etc. Can't know for sure - the closed form solution I need is the following to get a full picture of the extraction:
Mass of coffee: 19.2g Mass of brew water: ? Temp of brew water if not >195°: Mass of produced coffee: ? Wet Grounds Mass: 45.2 Dilution Mass (amount of water added to produced coffee): ?
That's enough to guess at the coffee extraction parameters with adjustment for taste. To get the complete picture, you'd need to dry the grounds to get the Dried Grounds Mass.
I assume you filled to the top with minimum bloom, so I'm guessing you used about 210g of water. You should have produced about 180g of approx 2% strength coffee that would be in normal range if diluted with another 70-100g of water (about 8.5 - 10oz). Using some assumptions, your absorption ratio is around 1.6 - much less than the 2.9-3.0 I've seen but more than my paper filter press brews (about 1.1 to 1.2).
Looking back at a couple of brews in the past, if you used 175°F water, extraction trends about 17.5%. It gets into the 18%+ at 200°F - keeping the contact time around 1 1/2 minutes.
Of course, YMMV. The beauty of tracking all of this is I can account for where all the water and the coffee went, usually with a total system loss of less than 2 grams of water during the process (less than 1% loss).
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
I don't do bloom. Which is to say, I consider vigorous stirring to be a necessary part of AP brewing, at the loss of control over some other possible factors. I use as much water as will possibly fit, including the addition of more after stirring, right before plunging. With all the stirring, any steep time would send it into overextraction, so I generally do this:
60 g/L overall ratio, grind optimized for this process just-off-boil water to almost overflowing vigorous stirring to knock down the bloom more water to almost overflowing a quick stir if I feel like I'm working fast plunge, fast as possible
I wouldn't try this with the inverted methods for fear of a hot mess. I do occasionally experiment with techniques that I read about here, but I guess I consider the AP to be fundamentally handicapped by its water capacity, and I haven't grown to like the results from the overdose/underextract technique it was made for. I do like its easy cleanup, and the fact that it exposes the variables to tinkering and/or intuition.
Here's an anecdote that might connect to the difference in pucks between paper and Disk:
Today I was washing the metal filter basket that my MIL uses in her drip machine. I noticed that when I pushed it underwater so that air was trapped in it, the air hardly bubbled through, and what did was very slow. But water rushed through it when trying to pick it up with water in it. Liquid passes through the metal filter more easily than gas. So there's that. Maybe it's the same with paper; maybe there's some difference that becomes significant?
I agree that stirring helps, but will not completely get rid of a very fresh (3 days post roast) bloom. In my experience, it works best to pour, stir to reduce bloom, pour again, etc. until I get to my target amount of water.
This morning: 18.9g coffee (half India/half Ethiopia Yirg) 230.1g water (100g initial pour, remaining over next 35 seconds) This is the max I think I can comfortably fit in an inverted Aeropress - the rubber plunger is 25% past the end of the tube, and I allow a few millimeters to install the cap and press a little bit.
total contact time before press: 1:10 (grind slightly smaller) Press time 12 seconds.
208.2g coffee 40.2g wet puck.
Awesome cup, only diluted to about 300g total. Absorption ratio approx 1.3
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
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