My long and rambling path to preinfusion/pressure profiling - Page 44

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AssafL

#431: Post by AssafL »

So for my machine the number I plan for is 28ml. This is measured by my flow meter (a digmesa) which I calibrated to different flow rates (but I cannot state a certainty figure for so take with a grain of salt). The number did not seem out of place as according to coffee tools:

Bev weight 36 grams (i.e. 32.4 grams water & 3.6 grams extracted solubles)
Dose 18 grams
and EY of 20%
The water weight would be 53 grams

So that the water left in the puck would be 53-32.4 or a bit over 20 grams. Hence I assumed the 28 was an okay number.

Obviously, if the TL tube is empty or the headspace is full or etc. the results will slide a few ml... Just had an ethiopean which packed really tightly. at 18gr it filled up at about 29-30ml.
Scraping away (slowly) at the tyranny of biases and dogma.

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Denis

#432: Post by Denis »

Then other people should take in consideration dead space (space between top of coffee puck and shower basket) and the TL volume. This means if you have your average free flow measured (4 g/sec) without any coffee then the amount of water to saturate the coffee is not 28 ml but more. Take in consideration that as swell.

Before hitting saturation the water takes all whole volume you throw at it. So let's say idealistic that you pump 4ml/sec and the volume to saturate everything is 40ml= 10 seconds before hitting saturation.

No? We talk as a general concept to any espresso machine, not a particular case. Or let me be more direct, why you take in consideration only the amount of water that your puck takes?

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AssafL

#433: Post by AssafL »

I think Jake's point is that when blooming ends (whatever 'bloom' means), one wants there to be no air and no dry coffee in the puck. (Or at least an evanescing number of dry spots in the puck).

So at that point the extraction will be most homogenic from all parts of the puck.

Jake - correct me if I am wrong.

At 28ml I get coffee through the puck with minimal drops in the cup. I guess Jake does as well. If one were to leave the 28ml for much longer it probably would eventually drip as the puck can only hold 20 grams or so.

PS - my 28ml being what it is - is known to Jake and others on this thread. From many many pages ago. It is more like "28" and "ml". Which is the reason i am amused that the VST meter sports a NIST certificate. Maybe my spatula can get one too? Really good spatula too...
Scraping away (slowly) at the tyranny of biases and dogma.

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Denis

#434: Post by Denis »

Preinfusion is the therm used from when you turn on the water income until pressure start to ramp up. When you see pressure starting to be more than 0 then the preinfusion is over.

I think that we have to agree that the value of water inside the brew chamber is more than 28ml. This value works for you cause you correlate it with TDS and/or the ratio. Or because your machine is build to work with that value (a measure or something in the software volumetric dose).

But for someone else it is better to work with the whole volume of water that is taken in the preinfusion state which can vary from machine to machine, but you can measure it with time and flow.

myso

#435: Post by myso »

Not sure if useful but i made a little experiment.

I have my rok's piston easily removable. So I take out piston pour off-boil water in the chamber, pull my shot, take piston out, pour excess water in sink, put piston back in, pump remaining water out of the puck to dry it, then knock the puck out and clean all parts.

So I weighed the water, dose, puck, shot, excess water etc. 199g in / 196 out below which probably means my water in measurement was a little off and I lost some for water out (wet equipment vs dry)
inputs:
water in: 183g. dose: 16g.
outputs:
shot: 47g. excess water emptied from chamber: 110g. water extracted from wet puck afterwards: 9.5g. puck weight after shot and air pumped thru: 30g.

Thus, puck soaked 14g of water and could bleed 9.5g out.
For 16g dose I would need 23.5g of water to saturate the puck. For a 20g dose it would mean 29.4g needed for saturation excluding water needed to fill headspace?

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Jake_G (original poster)
Team HB

#436: Post by Jake_G (original poster) »

AssafL wrote:Jake - correct me if I am wrong.
Correct. With my machine, it is between 25 and 30ml that I see drips if I take water debit and multiply by time with a fudge factor for the S-curve pressure response. The response is more predictable with a steady decline in available flow, and I think this is purely because it does a good job of limiting any appreciable pressure during the soak. No pressure increase, no corresponding drop in flow from measured water debit, better chance of timing it right with my crude methods.
Denis wrote: Before hitting saturation the water takes all whole volume you throw at it. So let's say idealistic that you pump 4ml/sec and the volume to saturate everything is 40ml= 10 seconds before hitting saturation.
I agree. But my machine has low headspace and the puck plus all the stuff between the solenoid valve and top of the puck seems to mimic Assaf's findings more than DC. Every machine will be unique, but many machines will be similar.
AssafL wrote:Sort of disappointing that mouthfeel and extraction don't increase simultaneously. Seems like slower darker pulls boast high EY but have less crema.
I didn't do a good job of communicating.

The faster soak shot flowed faster and had better mouthfeel than the slower soaked shot. Both shots bloomed and both were ridiculously over-extracted (coffee was Malabar Gold mixed with a lightly roasted Colombian Java). I think with lightly roasted SO coffees that need higher EY%, there is a legitimate strategy to hitting them hard to stir up the puck and move some fines and do whatever other magic needs done to improve mouthfeel and roll it back to zero flow before drips form and let it bloom.

I think blooming is a multi-faceted process, but that there is some actual bloom taking place, as would in a pour-over. The other part is the diffusion and absorption process whereby the puck does what a dry sponge does and soaks up the water, expands, and gets soft. I don't claim to understand what's going on at the molecular level, but I do know that capillary action does draw liquid into the puck the question remains of what else is going on in there. But that's for another epiphany-driven discussion...

Anyway, I'll pick up some fresh beans today and try a few more strategies to see if my hunch is correct. It seems counter-intuitive that you have a strategy that increases EY% through higher TDS and yet increased mouthfeel is not an automatic byproduct. This set of facts makes me think mouthfeel is definitely a function of emulsification, and that faster initial flow rates must somehow increase this. The good news is that blooming doesn't seem to decrease it...

Cheers!

- Jake

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AssafL

#437: Post by AssafL »

Denis wrote:Preinfusion is the therm used from when you turn on the water income until pressure start to ramp up. When you see pressure starting to be more than 0 then the preinfusion is over.
Well, PI is a rather ill defined term. It means what it means to whomever hears it. It used to be first drops as well. Especially for lever users. 2 things happen to the puck during PI:
1. Water displaces the air on the puck. This happens until fingering flow reach the pores in the basket.
2. The fingers of the flow then expand adding more solumbles to the coffee.

When pressure is applied flow continues. If step 1 was not completed puck Will seal and pour slowly. If step 2 wasn't complete EY would suffer.

Where you decide to end PI is up to you.
Scraping away (slowly) at the tyranny of biases and dogma.

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Jake_G (original poster)
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#438: Post by Jake_G (original poster) »

Denis wrote:Preinfusion is the therm used from when you turn on the water income until pressure start to ramp up. When you see pressure starting to be more than 0 then the preinfusion is over.
This is somewhat debatable. Preinfusion is a misnomer no matter how you look at it. I don't disagree with you in practice, but a shot that preinfuse with 2.5bar line pressure is very different than one that preinfuse at 9 bar, granted the water debits will be very different between the two.
I think that we have to agree that the value of water inside the brew chamber is more than 28ml. This value works for you cause you correlate it with TDS and/or the ratio. Or because your machine is build to work with that value (a measure or something in the software volumetric dose).
With an empty basket, yes. With a space-filling dose of coffee in it, I'm not so sure. It all depends on the geometry of the group, but a 58mm basket holds about 2.6ml per mm of headspace. Those who practice the nickel test or similar to set the headspace between 2 and 3mm, we have 5-8ml in addition to the roughly 1:1 of a dry puck plus the vias in the group. I'm pretty comfortable saying that in my group, after a flush to get water in said vias, that it takes 25 to 30ml to saturate the puck...
But for someone else it is better to work with the whole volume of water that is taken in the preinfusion state which can vary from machine to machine, but you can measure it with time and flow.
Sure. All machines are different, but this is not a hard factor to work out. Furthermore, once you take the mystique out it by measuring it, you find that it is quite repeatable with similar doses. More headspace disproportionately increases the volume needed, do to the empty space taking much more water to fill than the puck can absorb.

Cheers!

- Jake

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AssafL

#439: Post by AssafL »

Jake_G wrote:This is somewhat debatable. Preinfusion is a misnomer no matter how you look at it. I don't disagree with you in practice, but a shot that preinfuse with 2.5bar line pressure is very different than one that preinfuse at 9 bar, granted the water debits will be very different between the two.
If the pressure rises prior to PI being completed the same thing will happen... Fingering flows into a (now) compacted puck... :)

PI will continue - unless the puck seals. But the extraction will suffer as the finger won't coalesce.

Mouthfeel may be better though...
Scraping away (slowly) at the tyranny of biases and dogma.

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Jake_G (original poster)
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#440: Post by Jake_G (original poster) » replying to AssafL »

Yessir