Monitoring extraction tail/flow rate

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entropy4money
Posts: 84
Joined: 9 years ago

#1: Post by entropy4money »

Hi,

I've managed to create a consistent shot in terms of extraction time and brew ratio. I've acquired quite experience obtaining a quality espresso, first by directly measuring weight as the shot was extracted and trying to get ~50% brew ratio in 25-33 seconds. After achieving this several times, I removed the scale and would only look at blonding, and measure output after extraction was done. I am able to get a very consistent output every time. The math is consistent, but taste is not... Even though all my shots are decent, about 1 out of 5 is that "perfect" shot. that "perfect" shot is very dense, complex and strong yet balanced, and very very sweet at the end.

I've noticed that monitoring the tail of the extraction indicates better than anything how the shot is going to taste like. Basically, when the tail looks like a very dark and thin "mouse like tail" at the beginning of the extraction, developing into a light brown and then clear at the end but remaining thin and "mouse like" I get that perfect shot. However, sometimes, the tail starts dark and thin, but then it gets thicker and starts looking more cylindrical, here the shot does not taste as good.

So my question is. What affects this? I mean, output weight is the same, brew time is the same, but taste is not. And the consistent difference I noticed is the extraction tail going from perfect thin mouse like tail to a thick annoying cylindrical thing. Is it temperature? variables out of our control? what is it!!!!!!? This is driving me insane.

neutro
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Joined: 10 years ago

#2: Post by neutro »

I'd say it's distribution in the portafilter, tamp and grind quality, etc.

If you use a bottomless portafilter, it's the difference between a uniform extraction on all parts of the puck and small geysers and channeling. You can have minor channeling that doesn't change much the flow rate, but instead shows up as preferential paths whereby some parts of the pucks are "unused" and others "overused", and would be hidden in a spouted portafilter; but I guess the viscosity and extraction level of the output is what causes the changes in the espresso stream in spouted portafilters.

entropy4money (original poster)
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Joined: 9 years ago

#3: Post by entropy4money (original poster) replying to neutro »

First of all thanks for your answer. I don't have a bottomless portafilter. It could be tamping. Do you have any suggestions? tamp slightly harder maybe?. Distribution seems very reasonable as it seems to happen more often when I am dosing 13-14gr. When I get a different bean and dose about 15gr this doesn't happen that often.

brianl
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#4: Post by brianl »

Grind finer and tamp lighter.

putting muscle into a tamp increases the likelihood of it being canted.

entropy4money (original poster)
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#5: Post by entropy4money (original poster) replying to brianl »

Thx Brian, I'll try this.

neutro
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#6: Post by neutro »

In the past months I was sure my technique was spot on, with the occasional geyser (in my bottomless portafilter) signalling a problem that I could fix in the subsequent tamp.

Now I recently paid more attention to the look of the extraction cone underneath the basket as well and was surprised to see differences between the shots. Some were much more uniform than others. Some had spots where no coffee was flowing at all. It seems like uniform extractions systematically produces much better shots, unsurprisingly.

How to achieve this however is more art and practice than science for me. Nutation of the tamper before applying moderate pressure seemed to help, but at this point I'm not sure if I'm just doing things in a ritualistic fashion.

For me the main driver seems to be... relative humidity. Temperature here is currently alternating between hot & dry, hot & humid, hot & rainy, and cold & rainy. When it's humid or rainy, grind does not need to be as fine and extractions seem much more uniform. Dry means I have to grind way finer and the extraction is much more prone to geysers and other troubles.

entropy4money (original poster)
Posts: 84
Joined: 9 years ago

#7: Post by entropy4money (original poster) »

It got really humid here lately and things got worst, so yeah relative humidity seems to make a huge difference. I ground a bit finer, made sure everything was even and tamped slightly. I also programmed a thermocouple that fits the top of the boiler of my Gaggia because I got tired of the temperature surfing thing; it would be so annoying that sometimes my freshly ground coffee would be waiting quite a long time before I could brew, which is obviously not ideal. I didn't program a PID, I just have a display with the temperature so at least I know where I am and I can time my grinding so I prepare the coffee right after grinding. You realize how huge the temperature variation in the gaggia classic's boiler is once you see it on the display of the thermocouple.

I am getting really good consistent shots now. Thanks for the help!!!

RepackEspresso
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#8: Post by RepackEspresso »

Blonding is a strange way to judge when to stop a shot - in fact I'd go as far as to say that it has no place in speciality coffee any more. Maxwell Colonna-Dashwood (multiple WBC finalist) wrote about blonding being an archaic concept a while ago. Here's what he said:

https://colonnaandsmalls.wordpress.com/ ... -espresso/

So, don't look for blonding - weigh the dose, weigh the output; it's the only way to be properly consistent.

JP

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Peppersass
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#9: Post by Peppersass »

RepackEspresso wrote:So, don't look for blonding - weigh the dose, weigh the output; it's the only way to be properly consistent.

JP
I agree that blonding isn't a reliable indicator, and that weighing the dose and output is the key, but it's a little more involved than just using a scale.

You do want to stop the shot when the desired beverage weight is reached (or, more properly, when the target brew ratio -- dose weight / beverage weight -- is reached.) That defines the strength of the shot.

But, depending on the grind, the desired beverage weight can be reached anywhere along the extraction spectrum from sour to bitter. The objective is to hit the target beverage weight exactly at the point where the shot is balanced. That's basically a trial and error exercise where you adjust the grind finer or coarser to extract more or less from the grounds, taste the result (and/or measure the extraction yield) and readjust the grind accordingly.

The beverage weight tells you when to stop. The taste or extraction yield tells you if you have the grind (flow rate) correct. If your grinder is consistent, once you find the right grind setting you can leave it there and pull every shot to the target weight.

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pizzaman383
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#10: Post by pizzaman383 »

Peppersass wrote:The objective is to hit the target beverage weight exactly at the point where the shot is balanced. That's basically a trial and error exercise where you adjust the grind finer or coarser to extract more or less from the grounds, taste the result (and/or measure the extraction yield) and readjust the grind accordingly.
I tried using blonding, tail flow rate, tail shape off the spout, time, volume, etc. It wasn't until I started doing exactly what you described that I started getting the best taste with excellent consistency.
Curtis
LMWDP #551
“Taste every shot before adding milk!”

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