My long and rambling path to preinfusion/pressure profiling - Page 41

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AssafL

Postby AssafL » Dec 25, 2018, 4:35 am

Being reminded of Xmas filtration cleaning I think have a theory for why this works so well. In continuation of the air being driven out during PI.

So phase 1 of PI is driving air in the crevices, nooks and crannies out. Otherwise the air would compress when pressure is applied, the density would increase and the puck would seal. This will occur until at least one finger (fingering flows) ends up at the bottom of the basket - and at that point the flow on it would aerosol (spritz). Unless a few more fingers coalesced into a nice flow.

So remember fingering flows?

Phase 2 (I hypothesize) is when we allow more fingers to coalesce. If we apply pressure when the first fingers hit the filter - flow would occur through that finger and it will take time for the rest of the puck to wet. If we wait - more fingers would coalesce. EY would increase for higher TDS.

Now why do we get less of the bitter stuff? I assume that if we pull from more % of the puck at once we end up with a tighter flavor Gaussian at each second of the pull. Less of the old stuff (sour - already extracted) but also less of the future stuff (bitter). I think Sam Law was trying to explain this to me a while back but I was stubborn and obtuse.
Scraping away (slowly) at the tyranny of biases and dogma.

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Jake_G
Team HB

Postby Jake_G » Dec 26, 2018, 9:03 am

Who could forget fingering flows?

AssafL wrote:Phase 2 (I hypothesize) is when we allow more fingers to coalesce. If we apply pressure when the first fingers hit the filter - flow would occur through that finger and it will take time for the rest of the puck to wet. If we wait - more fingers would coalesce. EY would increase for higher TDS.

I think this makes sense. Similar basically by "forcing" more even flow through the puck by not allowing any one finger to have priority, you get not only more even extraction in the first finger, but better extraction throughout.

AssafL wrote:Now why do we get less of the bitter stuff? I assume that if we pull from more % of the puck at once we end up with a tighter flavor Gaussian at each second of the pull. Less of the old stuff (sour - already extracted) but also less of the future stuff (bitter). I think Sam Law was trying to explain this to me a while back but I was stubborn and obtuse.

Agreed. If water has permeated more of the puck, it has a harder time over-extracting any one part of it. You can have a longer pull time with hardly any risk of over-extracting as long as the puck integrity isn't compromised.

Got to go. Time to go scrub some solids from a cake filter.

Cheers!

- Jake

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AssafL

Postby AssafL » Dec 26, 2018, 9:59 am

Jake_G wrote:You can have a longer pull time with hardly any risk of over-extracting as long as the puck integrity isn't compromised.


And that last part is mostly taken care of by severely limiting water debit.

I think that we have rambled enough to fully understood the mechanical aspects of espresso extraction:I think we can even use a caliper to measure the headspace, calculate volume, and do the PI math on Excel. I think the mathematical model is simple enough.

Now only the act of grinding has its little halo of magic. Albeit I am somewhat suspicious of the exit chutes as being of more importance in the act of grinding than we give them credit for.
Scraping away (slowly) at the tyranny of biases and dogma.

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Jake_G
Team HB

Postby Jake_G » Dec 26, 2018, 11:51 am

AssafL wrote:Now only the act of grinding has its little halo of magic. Albeit I am somewhat suspicious of the exit chutes as being of more importance in the act of grinding than we give them credit for.

Oh?

Do tell...

Now that we've got full control of our water debit through one mean or another, I've got half a mind to try something drastic to see just how how much of a shot saver this whole process can be.
Image

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AssafL

Postby AssafL » Dec 26, 2018, 2:22 pm

Ugh NOoooo!

Please don't prove to us the a 50$ Krups is the equivalent to Denis' latest grinding masterpiece... Krups will end up selling their entire stock online in 23.87 seconds....

But you won't prove it... The boulders will kill it... Maybe if you grind, and sieve, grind and sieve....

Regarding the exit channels - it was something John Bicht remarked on in the VL M3 Grinder Thoughts thread.

Versalab M3 Grinder thoughts

versalab wrote:Unless...we have encountered flat burrs with an excessively large exit channel. The manufacturer did not grind the working surface of the burrs far enough. In some cases espresso could not be made with the burrs almost touching.


Hmmm. So these chutes let the boulders out. So two thoughts:
1. If the chutes are too large, the escaping boulders are too large and EY will suffer....
2. If there are too many chutes, there will be a lot of un-percolated boulders (coffee) in the puck....
Scraping away (slowly) at the tyranny of biases and dogma.

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Jake_G
Team HB

Postby Jake_G » Dec 27, 2018, 1:09 pm

It was a joke :P

But I may try it anyway just for kicks. No sieves, just grind it Turkish and do a long soak in the basket to see what comes out the other side...

AssafL wrote:Hmmm. So these chutes let the boulders out. So two thoughts:
1. If the chutes are too large, the escaping boulders are too large and EY will suffer....
2. If there are too many chutes, there will be a lot of un-percolated boulders (coffee) in the puck....

Ok, I'm with you now. I thought you were referring to the chute from the burrs out of the grinder body.

My understanding of the chutes in the burrs themselves is that on EK43 brew burrs they are what made EKspresso a thing. Basically even with the burrs touching, the boulders escaped and you had to pull a long shot. Oddly, this didn't result in poor EY%, but I suppose that's only because of the lungo shot nature of EKspresso.

I wonder what would happen if the outer ring of the burrs was ground smooth; teeth terminating in a solid ring and all ground coffee must pass through the gap in the burrs. In theory no boulders, but I suppose the burrs would be highly susceptible to loading up and jamming. There must be a reason the chutes are there. I imagine the size and quantity is a bit like sizing dimples on a golf ball. Too big and too few and you just have a deformed blob. Too small and too many and you have normalized the surface and they are effectively not there. Some sort of golden ratio must exist between the quantity and size of the chutes to make a good espresso burr.

Cheers!

- Jake

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Jake_G
Team HB

Postby Jake_G » Jan 10, 2019, 9:35 am

Happy New Year Everyone!

Hope everyone had a nice holiday season and is enjoying a well caffeinated 2019.

I finally got a good video of a blooming espresso shot. This one was a proper 90 second ordeal, with a 25-ish second slow pre-brew at line pressure (should have only been 15, but oh, well) followed by a 30 second bloom and then a 36-ish second shot. This was Peter's home roasted Sweet Maria's New Classic Espresso Blend and wow. First off, the roast on this was exquisite in terms of capturing flavor. No grassy notes or any hint of under-development, but also no smoky, toasty, ash flavors of a roast taken further than I usually prefer. Its sweet but juicy and bright, full-bodied and has a buttered-toffee finish. It pulls extremely well just as a non-profiled shot, so this was overkill, but I wanted to see what would happen. :wink:


Cheers!

- Jake

Bunkmil

Postby Bunkmil » Jan 10, 2019, 10:41 am

Hi Jake,

That looks like a good shot!

Can you tell me more about the last part of your extraction (the shot) ? Is it a flat pressure, a declining pressure, a flat flowrate, etc... ?

I am just trying to figure out how I would program that step on my DE1.

I haven't read the whole thread so sorry if you already wrote about that.

Thanks!

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Jake_G
Team HB

Postby Jake_G » replying to Bunkmil » Jan 10, 2019, 11:52 am

David,

Silly me for not calling that out! I put details in the YouTube post but forgot to mention it here. The shot is straight (wide open flow, ~8 bar) for the first 15 or 16 seconds after the pump is engaged. I begin a declining pressure pofile just after the streams coalesce with the intent of maintaining roughly 1g/s into the cup.

Cheers!

- Jake

Bunkmil

Postby Bunkmil » Jan 10, 2019, 12:20 pm

Thanks for the info!

Then I guess the profile would look like this on my DE1 :

1.5ml/s until 3bar
30s bloom
8bar for 15s
1ml/s until the end of the shot