Where do we want fines in the puck?

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mikeness
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#1: Post by mikeness »

In the quest to a beautiful extraction from a VST basket / naked portafilter (thought I was awesome, then got VST... not so much :roll: ), I've been experimenting with various distribution techniques.

WDT is always my de facto technique as it gives me the most even extraction visually. I have noticed, though, that the technique results in a blatant increase in the fines in my cup (enough to be cautious of my last sip). I'm assuming then that by stirring the grinds, the fines in the original un-tamped puck find their way to the bottom of the basket. During extraction, those fines are then the first to get pushed through the basket holes and voila - fines in my cup!

So I have a good idea what's going on as the fines don't appear if I simply groom the top layer (Stockfleth's) or don't let the needle go to the bottom of the basket when WDT'ing. Also, when only using Stockfleth's, the pour is much quicker without major channeling.

Knowing that fines are an critical factor to an espresso pour, I'm just curious as to your thoughts on the positives/negatives of the where the fines are in the puck? Any sort of agitation of the un-tamped puck seems to create a concentrated bed of fines that slows the pour...

Marcelnl
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#2: Post by Marcelnl »

Interesting point, I also wondered about this as I also have noticed there is a difference when doing WDt and I also atrributed part of it to the distribution of fines. Lacking the equipment to analyse I just stopped doing WDT and started doing some surface distribution before tamping (i do use the doser of the SJ but without the flap and with schnozzola and vanes). This seems to work quite good, not being able to see channeling due to the lack of a bottomless PF I have to stick to taste buds Mk 1 as test equipment....
LMWDP #483

DeGaulle
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#3: Post by DeGaulle »

I think this could be grinder-dependent. I was experiencing some fines from day 1 when I bought my Macap M2 grinder. I just switched to a Compak k3 for a more accurate grind adjustment and it seems to give fewer fines in the cup. Also I notice that with a grind setting that gives me a 1.5" oz double with 15 gram doses in some 25 seconds the flow dynamics are different for each grinder. With grinds from the M2 it takes longer for the first extract to exit the spout and the flow rate catches up after that. Just me guessing, but it might be that with the Macap a compact layer of fines forms more quickly, initially stalling the flow rate just a little longer before the puck swells and the extraction proceeds. WDT did improve shot consistency while I was still using the M2 but I did not observe an increase in fines in the cup. Using a 14 grams VST-ish basket gives me the minimum of fines, with the K3 these are next to none.
Bert

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weebit_nutty
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#4: Post by weebit_nutty »

I've always wondered this myself, actually. So it's a great topic. My theory is that fines with vertically even distribution of fines is more prone to spritzing than ones that have an even layer of fines at the bottom of the puck. My reasoning is that the latter will cover every hole in the basket evenly producing even flow resistance from all holes. The former, however will have some holes covered by bigger particles, leaving larger gaps and other holes covered by finer particles leaving smaller gaps. As we all can agree water travels to the path of least resistance so the flow going through the larger gaps can spritz under the same pressure that allows smooth flow through the smaller holes. If pressure is lowered whereby optimal flow comes out of the larger gaps, then the smaller gaps not flow at all due to too little pressure, resulting in dead spots in the extraction. I hope my reasoning made any sense.

Next time I'm in front of my machines I'm going to test this by simply bumping and tapping the basket to sift the fines to the bottom, covering all of the holes evenly (or as even as I can hope) and pull a shot. Then pull a shot without doing this. I'll let you know what I find.
You're not always right, but when you're right, you're right, right?

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aecletec
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#5: Post by aecletec »

When WDT'ing I would suspect that a simple explanation is that agitation of the grounds near the basket holes is what allows them to get stuck and/or work their way through the holes during extraction. Quite a few fines can get through the holes in my baskets by tapping on a silicone mat and they don't get through into my cup...
That fines in the whole puck are affected seems like a logical leap? How many fines are in a puck compared to what's in the cup at the end to guesstimate this compared to what's near the basket holes from the start?

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weebit_nutty
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#6: Post by weebit_nutty »

aecletec wrote:How many fines are in a puck compared to what's in the cup at the end to guesstimate this compared to what's near the basket holes from the start?
I imagine it would vary greatly from basket to basket, grind to grind, roast to roast, etc. But it's my opinion it matters greatly and dictates the extraction evenness.
You're not always right, but when you're right, you're right, right?

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aecletec
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#7: Post by aecletec »

So my question is, how do we measure to verify this?

Marcelnl
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#8: Post by Marcelnl »

I'd say that without a decent lab setup you"ll not be able to measure, but why would you?
Find a technique, or rather a combination of techniques that work for your specific combination and enjoy the result.
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aecletec
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#9: Post by aecletec »

Sticking to a technique and quiet enjoyment isn't really what internet forums are for, now is it? ;)

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weebit_nutty
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#10: Post by weebit_nutty replying to aecletec »

Part of me always thinks "Well, what does your mouth tell you?", but I am in agreement with you on this point. It's an interesting question and not something that I think has been tested before. Perhaps we might bring this over to the Socratic guys.. They are a highly inquisitive bunch and their work is to conduct comprehensive tests for answers to these very types of questions. Especially in lieu of recent claims by Matt Perger on tap leveling the puck (which I think does exactly what I was suggesting--sifts the finer grounds down the basket over the holes).
You're not always right, but when you're right, you're right, right?

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