Puck raking chokes espresso machine compared to WDT?

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Extractionator

#1: Post by Extractionator »

Hi,

I have a Sage Barista Express and currently it makes reeally good espresso. I love it!
From the beginning I was using WDT with a selfmade WDT tool made out of 0.4mm needles (like the Decent tool).
I always use "deep" WDT, going around the coffee inside the portafilter in slow/steady circular motions, making sure the tool touches the bottom and the sides of the filter.

I have 17 gramm in shots which take around 30 seconds to complete with ~36g of coffee out. No bitterness, no sourness, sweet, perferct in my opinion. (but maybe it could be better?)

Now my problem: I was thinking: What happens if I only try puck raking (leveling only the top of my coffee bed with the wdt tool)? My expectations were that the coffee would flow quicker since the distribution should be less ideal -> maybe channeling would occour. But actually what happens is that my machine chokes, only drips coming out. I really can't explain this in my head. I tried it 3 times and I kept everything else in my workflow the same times:

-) Grind in portafilter using a funnel, moving the portahead while grinding to get a rather even bed of coffee from the beginning.
-) WDT (or puck raking)
-) 2x verticall colapse using the counter top
-) distribution tool on lowest setting
-) tamping using a palmtamper.

So I think tamping can not be issue using this tamping workflow.

My only guess why this is happening, is that my form of WDT maybe actually creates channeling instead of mitigating it? Hover the shots taste really good and I see no signs of channeling in the puck when I look from the top. I am so confused. Maybe I have channeling I did not notice it? Does this mean my grind is too coarse? ...

Please let me know if you need more informations or pictures.

Any help is very welcome. I don't want to waste more coffee :)

apoopoo999
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#2: Post by apoopoo999 »

Most grinders with a horizontal exit chute will compress the grinds into the shape of the chute as it pushes the grinds into your portafilter. This causes the grinds to come out in clumps and inside the clumps the particles sizes are grouped together. So basically your coffee grinds ends up in the portafilter not evenly distributed. You will have a clump of fines in one spot and tamping this clump of fines creates a spot that will choke the extraction. This is why some grinders needs wdt and some grinders don't. The grinders that can spit the grinds out in a nice fluffy pile usually doesn't need wdt.

Btw channeling never tastes good

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Extractionator (original poster)

#3: Post by Extractionator (original poster) »

Thanks for the answer!

So basically you are saying there are some clumps which contain more fine particles than other clumps which causes the machine to choke when they come together? I never thought of that. So basically you say my grind size is good and I should continue using WDT instead of making the grind more coarse?

I always thought that if a grinder creates clumps that the fines are still evenly distibuted inside of the clumps.

Jeff
Team HB

#4: Post by Jeff »

WDT is all about uniformity and repeatability. Even with "the best" grinders, full-depth WDT has been shown to reduce shot-to-shot variance. The reason behind this is hypothesized to be more uniformity throughout the puck.

Extractionator (original poster)

#5: Post by Extractionator (original poster) »

Thx! So you also think that undistibuted fines are the problem in my case when I don't use WDT?

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decent_espresso
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#6: Post by decent_espresso »

I've long argued that given two pucks that have the same grind setting, and same dose weight, whichever puck slows the espresso down more, is the puck with higher integrity, and is the superior one.

A typical way to measure this is to make two espressos with different puck prep techniques, same grind/dose/in-cup weight, and whichever shot took longer to extract, had the superior puck prep.

As to the fines migration theory proposed above, here is how you can resolve that question:
  • grind into a milk jug,
  • shake the grounds to homogenize the particle size distribution
  • and then dose into a portafilter.
  • Then do your deep-WDT vs shallow raking on each
  • extract to the same in cup amount
  • the shot that took longer, had greater puck integrity and less channeling.
If you find that shallow raking chokes the shot, then I'd recommend a coarser grind, shallow raking, and compare the shot taste to the finer-grind-deep-WDT. Whatever tastes bests: do that.

Extractionator (original poster)

#7: Post by Extractionator (original poster) »

Thanks for the detailed answer!

I will try your test next week and I will post the results here. I am also very open to more answers on what else could possibly cause my describt observation. I read a lot about fines (Scott Rao etc.) and that they will accumulate together at the bottom of the portafilter during the espresso shot and restricting the flow. And because I move my portafilter around during grinding I am not really sure if too many fines in one spot are the reason. But I will do the tests and we will see!

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decent_espresso
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#8: Post by decent_espresso »

Extractionator wrote:And because I move my portafilter around during grinding I am not really sure if too many fines in one spot are the reason.
I agree with you, it's unlikely that you have nonhomogeneous grinds distribution if you're doing that.

For me, Occam's razor applies, and the simplest answer is that your puck has greater integrity with raking vs deep WDT. If you go coarser, and shallow raking gives you a similar flow rate to deep WDT + finer, that'd be what I'd argue that in your case, shallow raking is getting you a higher puck integrity than deep WDT is.

Extractionator (original poster)

#9: Post by Extractionator (original poster) »

Thank you again. It's really cool to have such a well known person in the coffee world answer my questions!

Ok, on monday I will try to go coarser with puck racking until I get the shot timing/taste I want. I think my current setting is too fine and the WDT creates a bit of channeling which allows the shot to go through faster compared to just puck raking. So actually it is very likely that I was having channeling issues all the time but I just did not notice it ... :/ Can't wait to test the result with the coarser grind.

After puck raking and coarser grind gives me the shot I want, I will again try it with deep WDT and the same coarser grind and compare the results. In this case I would expect the shot to take longer. If not, then my WDT technique must be way off.

Will post the results on Monday!

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decent_espresso
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#10: Post by decent_espresso »

Extractionator wrote:Ok, on monday I will try to go coarser with puck racking until I get the shot timing/taste I want. I think my current setting is too fine and the WDT creates a bit of channeling which allows the shot to go through faster compared to just puck raking. So actually it is very likely that I was having channeling issues all the time but I just did not notice it ... :/ Can't wait to test the result with the coarser grind.
Can you tell us how dark roasted your beans are? Light/medium/dark ?

I ask, because dark roasted beans are very forgiving, and still taste good even with significant channeling. By "good" I mean "what people expect dark roasted beans to taste like".