What went wrong with my extraction?

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SineQuaNon726

#1: Post by SineQuaNon726 »

Hi everyone, it's my first post here on the forum. Nice to meet you all.

I have recently upgraded my espresso machine to the Lelit Bianca (I am using a Niche Zero grinder) and I am starting to get weird extraction that I did not experience with my old Breville. FYI, the receipt that I did was 4s pre-infusion with a 4s rest, then brew at somewhere between 9 - 9.5bar. 18.5g in 40g out in 24s (from first drip).

See picture below for the extraction, the few issues I am having:
1. The coffee looks pretty "thin" out from the basket (Not sure how to describe it properly but it doesn't have the kind of full body that coats the bottom of basket)
2. there are some random areas that doesn't have liquid flowing through.


I know the first thing that comes to your mind is most likely bad distribution and channeling. The way I prep my puck is:
Dose from the Niche Zero dosing cup -> Palm tap to flatten the ground -> Distribute using a leveler -> Tamp
and here's how the puck looks like


For this particular shot I also use a puck screen, here's how the puck looks like after pulling the shot.


Taste-wise it's decent, still dialing in my shot but overall I don't taste anything funky. The look of the extraction really bugs me though. Hope fellow coffee experts here can give me some insight on what went wrong. Thanks in advance.

EDIT: Some of extraction metrics for reference. I got 9.3% TDS, translate to 20.1% extraction yield.

Jeff
Team HB

#2: Post by Jeff »

How light is the coffee?

Leaving the dry spots aside, light roasts often don't look pretty like classic espresso roasts.

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SineQuaNon726 (original poster)

#3: Post by SineQuaNon726 (original poster) » replying to Jeff »

I would say it's more or less city+ roast, definitely not the classic dark roast.

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cafeIKE
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#4: Post by cafeIKE »

Uneven flow = uneven distribution.

What is your work flow from the Niche to lock-in?
There does not appear to be much difference in depth between a dry and wet puck. How much clearance from puck surface to shower screen? Perhaps grind a dot finer and use 1g less coffee?

FWI, I grind the Niche directly into the PF w a collar and use a home made spreader to distribute w no WDT. Perfect flow every time from all kinds of roasts.


Nunas
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#5: Post by Nunas »

Like Ian, I also grind right into the PF using a similar collar/funnel (from OE). I then level with a cloverleaf distributor, without significant tamping pressure from the distributor. I rarely use my tampers at all. Furthermore, I infuse by lifting the e61 lever until my brew head pressure gauge reads about 3-bar, then wait for 15 to 20 seconds with it in the middle position, or until a small amount of coffee has dripped out of the PF. I believe this works because the puck has time to dampen evenly and to swell to seal, and perhaps close any voids. But, heck, I've no idea what's really going on in the PF :lol: This usually gives me near perfect results for most beans. I used to do all the above plus tamp. I stopped tamping because doing that seemed to increase the likelihood of channeling; again, I've no idea why.

coffeechan

#6: Post by coffeechan »

Any RDT or WDT? A Leveler does not always do the complete job of distribution. It grooms and prepares the top layer of coffee to be tamped, leaving the bottom more or less undisturbed. RDT will help alleviate static for less clumping and WDT will break the clumps after dosing. WDT or RDT may not be necessary depending on the coffee, grinder, humidity. I would do them though if you are not getting the results you want as a check to your workflow.

Jeff
Team HB

#7: Post by Jeff »

My suspicion is that the puck isn't getting fully wet before you start extraction. The ramp-up of a rotary pump vs. a vibe pump can be very different. even if the timing is the same.

If you video the bottom of the basket, do you get even wetting of the holes at the start?

In my experience, most of the profiles I work with have the basket at least evenly weeping before ramping up pressure, if not starting to drip. With a darker roast, the time before pressure-up may only be a second or two. With light roasts, this may be several seconds of "hold" time. It seems reasonable to believe that if the grinds aren't uniformly wet when you ramp up pressure, the dry portions may never get well wetted and extracted, with the flow tending to the already wet sections.

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SineQuaNon726 (original poster)

#8: Post by SineQuaNon726 (original poster) »

Thanks everyone for your input. I have tried a few things but the issue is still there

1. Reducing the dose from 18.5g to 17.5g with a slightly finer grind
2. using a needle type of WDT similar to the Duomo The Eight but cheaper (Duomo to me is a bit overprice for the purpose it serves)
coffeechan wrote:Any RDT or WDT? A Leveler does not always do the complete job of distribution. It grooms and prepares the top layer of coffee to be tamped, leaving the bottom more or less undisturbed. RDT will help alleviate static for less clumping and WDT will break the clumps after dosing. WDT or RDT may not be necessary depending on the coffee, grinder, humidity. I would do them though if you are not getting the results you want as a check to your workflow.
I didn't use a RDT, the humidity here is on the high side, not too much of a electrostatic issue here IMO.
Jeff wrote:My suspicion is that the puck isn't getting fully wet before you start extraction. The ramp-up of a rotary pump vs. a vibe pump can be very different. even if the timing is the same.

If you video the bottom of the basket, do you get even wetting of the holes at the start?

In my experience, most of the profiles I work with have the basket at least evenly weeping before ramping up pressure, if not starting to drip. With a darker roast, the time before pressure-up may only be a second or two. With light roasts, this may be several seconds of "hold" time. It seems reasonable to believe that if the grinds aren't uniformly wet when you ramp up pressure, the dry portions may never get well wetted and extracted, with the flow tending to the already wet sections.
I think you have a legit point here, if the puck isn't uniformly wet, the water will go through the path that is wet so the area that isn't soaked will not have water passing through. Will do some testing in this regard.

In that case, would you recommend extending the pre-infusion period for a bit to ensure the puck gets wet before building up the pressure? I think 4s is kind of optimal for my taste, further extending the pre-infusion begin to create that harsh acidity. Alternatively, maybe I can try a slightly slower ramping up of pressure to 9 - 9.5bar.

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cafeIKE
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#9: Post by cafeIKE »

Try reducing the pressure to ≈8.5 bar on the puck.

I know it's heresy, but IMO, WDT does not ensure even distribution. It will break up large clumps, but I've always lived near the coast and never had the horrible clumping issues as shown in some images. WDT creates a lot of furrows, possibly migrating fines to the basket bottom. IMO, the Niche directly into the PF and the spreader precludes it and provides a more constant cup with the coffees used here.

coffeechan

#10: Post by coffeechan »

I find WDT hit or miss. Sometimes I do it and sometimes I don't depending on how fluffy or clumpy the grinds are.

Depending on the grind settings, pre-infusion could take up to 13-15 seconds depending on how fine I tend to grind. The default PI pressure for me is 55% of 9bar and first drops come out at 13-15s (indicating that the puck is saturated and ready to extract) so 4s pre-infusion and 4s rest could be too short. Adjust the flow after depending on the type of coffee and taste.