Comments on La Marzocco Linea Micra Espresso Machine Review - Page 21

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iploya
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#201: Post by iploya »

From Jeff: Annoyances...The shower screen has a protruding screw head...I found that I had to down-dose baskets 1-3 g compared to my other machine to keep reasonable clearance.
I have to down-dose at least 2g as well to avoid imprint in the dry puck. Even then, I still get an imprint from the screw head in the wet/expended puck. For example, here's an expended 15g puck in a 17g basket, even using the convex tamper:



Would this cause channeling as well? On the one hand, it makes sense that any divot in the bed can be a weak point. But on the other hand, there is no flow coming out of the center of the screen occupied by the screw, so I wasn't sure it would. Thanks.

It also occurred to me, perhaps that's the reason LM provides a convex tamper. To displace the volume of coffee in the puck so the center is slightly lower for more clearance for the screw. (Not sure if someone has already proposed this.)

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baldheadracing
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#202: Post by baldheadracing »

iploya wrote:Would this cause channeling as well?
No. A divot in the spent puck is normal and expected on machines that have such screws. The puck can be sucked upwards at the end of the shot by the action of the three-way solenoid, and/or the puck expands once the pressure is released at the end of a shot.
iploya wrote:It also occurred to me, perhaps that's the reason LM provides a convex tamper. To displace the volume of coffee in the puck so the center is slightly lower for more clearance for the screw. (Not sure if someone has already proposed this.)
I do not know what LM was thinking, but to me the biggest reason to use a convex tamper is that extraction is less sensitive to convex tamps that are not perfectly level. Even in Italy where every café uses a convex hand tamper, the tampers built into old-school doser grinders - so the tamps are always level - have flat bases.
-"Good quality brings happiness as you use it" - Nobuho Miya, Kamasada

espressoren
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#203: Post by espressoren »

PaulTheRoaster wrote:I was thinking of convection from the disc but you're right. It seems like my bayonet ring and pf don't get that hot compared to my previous machines but I don't have any data.
My portafilter is hot enough to burn me in the mornings if I'm not careful prepping the puck. Maybe not full boiler temp though.

espressoren
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#204: Post by espressoren »

baldheadracing wrote:
I do not know what LM was thinking, but to me the biggest reason to use a convex tamper is that extraction is less sensitive to convex tamps that are not perfectly level. Even in Italy where every café uses a convex hand tamper, the tampers built into old-school doser grinders - so the tamps are always level - have flat bases.
I was thinking it makes for more consistent extraction. Almost every bottomless extraction you see starts with a ring of espresso around the outside then quickly fills in to the center. Clearly the outside edges are first to saturate and "easiest initial path". A concave puck would compensate for that somewhat, and like you said may be more forgiving. It could also have an effect of "packing the wall" so to speak, when you tamp downward the tamper pressure actually pushes the grounds out toward the edges somewhat rather than straight down. Probably improves the seal along the basket wall.

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baldheadracing
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#205: Post by baldheadracing »

espressoren wrote:... Almost every bottomless extraction you see starts with a ring of espresso around the outside then quickly fills in to the center. ...
This can be happening due to the basket bowing in the center due to extraction pressure, but the only way I have been able to test this is between new-old-stock (1960's/1970's) baskets vs. current production of the "same" basket. The old baskets do not donut extract, but the new ones do. The old baskets are thicker and heavier. However, this is not a great experiment.
-"Good quality brings happiness as you use it" - Nobuho Miya, Kamasada

espressoren
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#206: Post by espressoren »

Regarding the portafilter temperature conversation, I tried to get some FLIR measurements. Almost forgot that reflective surfaces don't show up, so the best I could do was slap a piece of tape on the portafilter and measure the temperature of that. These are somewhere between 15-30 minutes of warming time, I don't know exactly since I was messing with the FLIR cam.




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Jaroslav
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#207: Post by Jaroslav »

cannonfodder wrote:That photo is deceiving. With an LM spouted portafilter and a 'standard' size demi cup, there is about 1/4 inch clearance FYI. Also as I noted in my writeup, the angled handle hangs down in the way and I smacked it several times with my cup which is why the stock portafilter has a straight handle. But yes, you could do it if you really wanted.
Thank you Dave, that's very helpful.
Jaroslav

Shakespeare
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#208: Post by Shakespeare »

I have great interest in the Micra and I want to THANK the contribution given by the Team HB for their exceptional reviews of the
Linea Micra.
I find their answers given to support their initial reviews to be honest, straightforward and very helpful.
And even if I not a buyer in the future. I learned a great deal reading their evaluations/comments of the Micra.
I appreciate and now (somewhat) understand the intricacies making espresso and the dedication needed.

Congrats to Team HB:: another_jim, cannonfodder, HB, IamOiman, Jeff and all contributors not mentioned.

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iploya
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#209: Post by iploya »

baldheadracing wrote:No. A divot in the spent puck is normal and expected on machines that have such screws. The puck can be sucked upwards at the end of the shot by the action of the three-way solenoid, and/or the puck expands once the
Thanks, Craig. That is a huge relief as I was wondering how big I'd have to go on the basket to avoid this wet imprint. My prior machine's screw is flush so it's not something I ever considered.

And while it may not have been the intent, the convex tamper does provide that extra little bit of clearance to help avoid disturbing the dry puck. I did a little "experiment" and I was able to put a full 14g dose of Saka Gran Bar into the 14g basket and not have to dose down.

First with a flat tamper (shows dry imprint).



Then WDT to loosen the grounds, re-level, and apply convex tamper (no dry imprint).

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Jake_G
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#210: Post by Jake_G »

iploya wrote:I did a little "experiment" and I was able to put a full 14g dose of Saka Gran Bar into the 14g basket and not have to dose down.
For what it's worth, I use that teensy dry imprint as a stupid simple "nickel test" with my GS/3. When the screw just leaves a mark, I know I'm at roughly the max dose for a given basket. You can push it a bit past that without ill effects, but it let's you know you're more likely to be down-dosing and grinding finer than up-dosing and grinding coarser with that basket.

For better or worse, having the built in puck clearance tester has never been a detriment to the quality of espresso I get out of the machine. (Although I do have plans for a flush-mounted shower screen and dispersion screw :mrgreen: )
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