Uneven extraction pattern
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jasonmolinari
I'm having a curious extraction "issue" that I can't seem to get rid of.
I seem to have this grinding with my Niche and also a Monolith Max flat. I've tried really emphasizing my WDT, I've replaced the shower screen, lowered extraction pressure from 9bar to 8.5bar, grinding finer, grinding coarse (coarser seems to help some but then my extractions are fast).
Extraction starts beautifully (3 bar line pressure), then suddenly will start extracting in a trefoil pattern. This seems quite consistent and I just can't figure out why!
Anyone have any good ideas of how I can address this issue?
Flavors are good, but something tells me it could be better!
PS: coffee is fresh from Olympia, about 10 days off roast, but I've also tried various coffees
PPS: general pulls are 16g in 32g out. And I've tried various baskets with varying levels of success to get rid of this trefoil breakthrough pattern
thanks
I seem to have this grinding with my Niche and also a Monolith Max flat. I've tried really emphasizing my WDT, I've replaced the shower screen, lowered extraction pressure from 9bar to 8.5bar, grinding finer, grinding coarse (coarser seems to help some but then my extractions are fast).
Extraction starts beautifully (3 bar line pressure), then suddenly will start extracting in a trefoil pattern. This seems quite consistent and I just can't figure out why!
Anyone have any good ideas of how I can address this issue?
Flavors are good, but something tells me it could be better!
PS: coffee is fresh from Olympia, about 10 days off roast, but I've also tried various coffees
PPS: general pulls are 16g in 32g out. And I've tried various baskets with varying levels of success to get rid of this trefoil breakthrough pattern
thanks
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Jeff
- Team HB
I'm not sure I'm seeing what you're seeing there.
The one thing that caught my eye is that the stream has gone translucent by the last 5-10 seconds of the shot. I don't know how your beans were roasted, but if that wasn't intentional (such as it might be with a light roast to balance acidity), you might want to try a shorter ratio.
If it is a medium or darker roast, you might also try without the line-pressure soak. At least in my experience, American-style espresso blends (or darker) are relatively easy to extract (compared to light roasts). They don't need the fine grind and soak to extract easily. I've found that espresso blends can get overly bitter with a soak and, for me, do better with not much more than a basket fill before ramping up.
The one thing that caught my eye is that the stream has gone translucent by the last 5-10 seconds of the shot. I don't know how your beans were roasted, but if that wasn't intentional (such as it might be with a light roast to balance acidity), you might want to try a shorter ratio.
If it is a medium or darker roast, you might also try without the line-pressure soak. At least in my experience, American-style espresso blends (or darker) are relatively easy to extract (compared to light roasts). They don't need the fine grind and soak to extract easily. I've found that espresso blends can get overly bitter with a soak and, for me, do better with not much more than a basket fill before ramping up.
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jasonmolinari (original poster)
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cafeIKE
- Supporter ❤
The water flow from the screen during the soak could be corrupting the puck with uneven wetting.
What does the pre flow look like?
What does the puck look like if your stop the shot where you would normally engage the pump?
How much screen impression is on the puck after a shot?
What does the pre flow look like?
What does the puck look like if your stop the shot where you would normally engage the pump?
How much screen impression is on the puck after a shot?
Ian's Coffee Stuff
http://www.ieLogical.com/coffee
http://www.ieLogical.com/coffee
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jasonmolinari (original poster)
Can you clarify "pre-flow"? the flow from the shower screen looks even and consistent across it.
After the shot the puck is soupy, but there is a visible impression on the coffee from the screen. I will take a picture next shot tomorrow morning
I never stopped the shot after pre-infusion and before pump. I can certainly try and take a picture. What would we learn from this ?
thanks!
After the shot the puck is soupy, but there is a visible impression on the coffee from the screen. I will take a picture next shot tomorrow morning
I never stopped the shot after pre-infusion and before pump. I can certainly try and take a picture. What would we learn from this ?
thanks!
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jasonmolinari (original poster)
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zfeldman
This ^^^^Jeff wrote: If it is a medium or darker roast, you might also try without the line-pressure soak. At least in my experience, American-style espresso blends (or darker) are relatively easy to extract (compared to light roasts).
Anything medium or darker can probably do a max of 3-5 seconds pre-infusion to prevent the initial water flow from the pump disturbing the puck.
And if doing 3-5 seconds at 3bar...probably shouldn't see any sign off liquid coming out.
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jasonmolinari (original poster)
you guys might be right. This morning I tried some shots with little/no preinfusion and was able to draw the pull out to a 2:1 ratio with the extreme early blonding in my first post. Flavor was good.
Sometimes I forget that not every coffee needs preinfusion for best extraction!
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zefkir
You're misinterpreting the flow out of the puck. If you look closely at what's happening at 12 o'clock, there is coffee exiting all the holes, but that coffee is just merging with the large stream situated left and right and leaving a hole seemingly empty space in the middle. This impression of uneven extraction is accentuated by the fact that the coffee exiting the holes is pretty translucent at this point, a thin layer of coffee will be invisible.jasonmolinari wrote:thanks for the tips. It's a medium roast. I'll try what you suggest.
The uneven areas of extraction are highlighted in this photo.
image
As to why it splits, it comes down to cohesion, the property of a liquid to stick to itself. As the extraction progresses, the liquid becomes closer to water and is less cohesive. So it splits.
With a preinfusion, you've front-loaded the extraction. Coffee matter still dissolves during pre-infusion. The first drops have more dissolved coffee in them, and the later part of the shot has less dissolved coffee in it because it's already been extracted.
Without preinfusion, the first drops have less dissolved coffee in them and the last drops have more dissolved coffee, the later part of the shot is more cohesive.
In short, it's not uneven extraction you are seeing, it's less cohesive liquid because the compounds that make it cohesive have already made it into the cup below.
Side note here: the lighter the roast, the less cohesion it will have, even at the very start. Not all coffee ompounds give the same cohesion.
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