Can we have a real debate on Silvia pre-infusion?

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sbrussell
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#1: Post by sbrussell »

I recently posted a topic on pre-infusing the Silvia which received little comment. Researching past postings, I find supporters of 1) the relatively expensive MLG kit that slowly steps up the pressure; 2) the VPT (Vanbloom pressure technique) that involves cracking open the steam valve to lower initial brew pressure; 3) adding an inexpensive switch to activate the 3-way solenoid without turning on the pump; and 4) simply turning on the brew switch for 1-2 seconds to admit water at 1-2 bar (that the vibe pump ramp up), then turning it off for a few seconds to allow the coffee to expand before turning the switch back on. I have been using 4) for some time with good results. I see it was also endorsed in a 10/20/10 post by Jonny.

Since I read (and I hope it was accurate) that an E61 pre-infuses at 4.2 bar, I fail to see the problem with a 2 bar pre-infusion to consolidate the puck. I have never experienced the sucking back or breaking up of the puck surface predicted by some.

I think anyone who uses a Silvia (and that's many) would want to know the simplest way to pre-infuse to prevent channeling which was a big problem for me before adopting the on-off technique. No doubt very careful attention to grind and tamping can minimize channeling, but with pre-infusion I find the grind and tamping much less critical (although the effect on flavor is something different).

It would be great to have a discussion about which of these methods works best and what their shortcomings are.

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Randy G.
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#2: Post by Randy G. »

#3 could theoretically be a problem because opening the boiler without activating the pump invites flash boil. Depending on the thermostat's "accuracy," (had to giggle when I typed that), the current state of the heating element (on, nearly off, off, etc.), temperature of the water, and altitude, this could go from unnoticeable to turning the beginning of the extraction into steam driven.
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dustin360
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#3: Post by dustin360 »

I briefly messed around with opening the steam wand slightly at the beginning of brewing. It works ok, but lets out precious hot water out. And because the silvias boiler is so small I worry about temp drop that is the result of bleeding that water.

Ive also messed around with the whole "flip the switch for a second, and then turn it back off" routine. I think as long as you dont let a ton of pressure build, the three way opening doesn't become an issue.

Though in the end, pre infusion seems kind of silly. Its a lot easier(in my opinion) to just distribute well and then tamp level. And as long as you dont bang the portafilter up into the machine you should be good to go.

sbrussell (original poster)
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#4: Post by sbrussell (original poster) »

Randy:
Maybe if I were better at grinding and tamping I wouldn't have trouble either. But the number of posts from Newbies (and I'm a semi-newbie) suggests I'm not alone. Some lever machine fanatics I know don't seem to worry much about tamping or channeling and I think that's because of the gentle preinfusion. I'd rather "cheat" that way (if you can call it that), get a decent flow rate, and worry about the subtlties of grind and tamping afterwards to improve the taste.

Anyway, idea 2 and 3 have gotten criticized. Idea 1 seems like expensive overkill on a machine like the Silvia. I'm waiting for the criticism of 4), the cost-free way I do it. Is someone going to tell me I'm crazy, the 3-way solenoid will destroy the puck when I turn the switch off after two seconds?

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allon
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#5: Post by allon »

I'd consider #4 to be more pre-wetting than preinfusing. I'd think the results would be different and more lever like with a steady build of pressure. You also won't necessarily get all the way through the puck you run the risk of fracture or side channeling, and migration of fines will be different.

*edit* note that maybe not; with a lever, doing a "Fellini" move you might expect the same issues with fracture, but it doesn't seem to happen *

#3 is a problem with a non-plumbed machine, true, but with line pressure, or kicking the pump a few times to goose it up to 3-4 bar it works pretty well.

If #4 works for you and you're happy with it, stick with that. If you're wondering if you can do better, and you're moderately handy with electrics, you can split the 3way and pump and experiment with an easily reversible hacked setup; if you don't get an improvement, you can roll back the changes and write your findings here.
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Randy G.
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#6: Post by Randy G. »

sbrussell wrote:Randy:
Maybe if I were better at grinding and tamping I wouldn't have trouble either. But the number of posts from Newbies (and I'm a semi-newbie) suggests I'm not alone. ...
I never stated that preinfusion was wrong nor had no value, nor criticized your applying it to your process. I preinfuse every extraction for five to ten seconds and find it very useful.

To get better at grinding you just need a better grinder.
There is nothing to tamping other then pressing down, level, on the coffee and then not disturbing the compacted mass before extraction.
Dose and distribution are another matter.
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pizzaman383
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#7: Post by pizzaman383 »

Has anyone considered modding in a Vivaldi S1 pre infusion chamber on a Silvia?
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erics
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#8: Post by erics »

Has anyone considered modding in a Vivaldi S1 pre infusion chamber on a Silvia?
https://www.coffeegeek.com/forums/espre ... ods/373954
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sbrussell (original poster)
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#9: Post by sbrussell (original poster) »

allon wrote:I'd consider #4 to be more pre-wetting than preinfusing. I'd think the results would be different and more lever like with a steady build of pressure. You also won't necessarily get all the way through the puck you run the risk of fracture or side channeling, and migration of fines will be different.

*edit* note that maybe not; with a lever, doing a "Fellini" move you might expect the same issues with fracture, but it doesn't seem to happen
The pressure build-up in the Silvia is non-linear: very slow for about 5 seconds then rapidly up to about 9 bar. I tested this with a Portafilter gauge cracked open to allow some limited water flow to simulate the flow of water through the puck. So there is the option to continue a little beyond 2 seconds. I've pulled the PF out after 3 seconds and the puck appears saturated and intact. I'm not sure of the delay time to enable the ground coffee to expand and compact. On lever machines it can be quite long without affecting the final result (so I'm told).

Does anyone know of a comparison of lever machines in terms of preinfusion pressure (minimal?), brew pressure (spring and manual pressure machines) and has anyone attempted to adjust a pump machine to simulate a lever machine?