Pre-Infusion and Extraction Time

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Anthony

#1: Post by Anthony »

I have been reading through suggested literature on brew pressure, and the issue of pre-infusion has surfaced time and again. I have a couple simple questions. First (on my Andreja), I gather that the lag at 4 bar for about 5 secs, before it ramps up to 9 bar, is the "pre-infusion." Is this the case? Second, since pre-infusion times vary from machine to machine; since pre-infusion can be done manually on other machines; and since there are machines with and without gliceurs (flow restrictors, relating to the initial build up of pressure), when one speaks about the length of time when pulling a shot (eg. 25-30 sec, say), is this generally timed from the moment the pump is turned on, and not after pre-infusion? Is this the convention? I mention this for simplicity in communication. So, when someone writes that he or she pulled at shot at X temp, at Y bar, and pulls the shot short at Z secs., I can more or less get an idea of what is happening and try it out for myself (otherwise it would be necessary for me, e.g., to add in a pre-infusion time ...).

Anthony

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cafeIKE

#2: Post by cafeIKE »

Time from pump on to first drop varies considerably from machine to machine. Ditto when the e61 preinfusion ramp peaks.

If all times are specified from the first drop of espresso, all prior variables are removed.

Even then, depending on flow through the puck, 30ml in 30seconds can vary tremendously in taste. A nice even pour will likely taste better than a choked shot that suddenly lets go and gushes for the last 10 seconds.

AndyS' Brew Ratio idea holds merit, but it's PITA to implement.

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another_jim
Team HB

#3: Post by another_jim »

There is a technical distinction between preinfusion and dwell time. Dwell time is just how long it takes from turning on the pump to seeing the first drop. Preinfusion is some mechanical arrangement to apply lowered pump pressure at the start of the shot.

The simplest preinfusion device is a gicleur, a 0.3mm to 0.8mm flow restrictor that reduces the pressure until the space between the puck and the top of the group fills. In order for it to work, there has to be space between the top of the puck and the shower screen. Some machines use water line pressure and delay the pump for a few seconds, others pulse the pump. The manual E61 has a spring loaded cylinder that ramps the pressure; the automatic E61 has a cavity so that the gicleur isn't dependent on the heapspace over the puck. Lever machines are the simplest and most flexible, since one can let the water soak into the puck as long as one likes before engaging the lever

Allowing the puck to soak reduces the chance of channeling during the shot. This part is pretty much confirmed fact. Whether preinfusion affects the taste positively, negatively or not at all is debated. My guess is that, as is usual when this happens for espresso variables, it means the effect is both small and dependent on a half dozen other things.
Jim Schulman

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cafeIKE

#4: Post by cafeIKE »

another_jim wrote:...In order of it to work, there has to be space between the top of the puck and the shower screen...
Interesting point. On the e61, there is some permanent 'headspace' between the water disperser and the back of the screen.

It's one of my thought experiments on how water entering the brew area diffuses into the puck and how the puck reacts with zero, some and a lot of room and how grind and compaction interact relative to channeling.

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AndyS

#5: Post by AndyS »

cafeIKE wrote:AndyS' Brew Ratio idea holds merit, but it's PITA to implement.
Whether the idea holds merit is for others to judge. But what's really a PITA for me is when people pretend to be really precise in measuring their shots volumetrically, and they never specify if they're using a bottomless pf or not, or how old the coffee is, or whether there's robusta in the blend, etc. What a joke.
-AndyS
VST refractometer/filter basket beta tester, no financial interest in the company

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HB
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#6: Post by HB »

Anthony wrote:...when one speaks about the length of time when pulling a shot (eg. 25-30 sec, say), is this generally timed from the moment the pump is turned on, and not after pre-infusion? Is this the convention?
One of the first questions new barista's ask is "When does the timing of the extraction start?" Of course few search before asking questions, so it's only a matter of time before someone else starts a similar thread, for example, "Timing a double shot?", "Timing of double vs. triple espresso", or "When to start timing from naked portafilter?" That said, you've raised another issue not mentioned in previous incantations: Does the timing include preinfusion?

I'll stick to my original answer: The extraction timing begins the moment the pump is engaged. For sake of completeness, most vibe pump espresso machines have dwell times around 5-7 seconds while commercial espresso machines equipped with rotary pumps may be barely 3 seconds. I don't think it's worth fussing about a few seconds one way or another when comparing notes with another barista.
Dan Kehn

Anthony

#7: Post by Anthony »

another_jim wrote:There is a technical distinction between preinfusion and dwell time. Dwell time is just how long it takes from turning on the pump to seeing the first drop. Preinfusion is some mechanical arrangement to apply lowered pump pressure at the start of the shot.
So, just to be clear, all preinfusions have/are a dwell time, but not all dwell times are necessarily preinfusions. This is to say that it just might take some time between turning on the pump and seeing the first drop on a certain machine, but there is not any dampening of the cake. Yes?
HB wrote: That said, you've raised another issue not mentioned in previous incantations: Does the timing include preinfusion?
Yes, Dan, that was the question I had, at least when reading the topic of preinfusion as it was mentioned in the other contexts of brew pressure. Thanks.
another_jim wrote:The simplest preinfusion device is a gicleur, a 0.3mm to 0.8mm flow restrictor that reduces the pressure until the space between the puck and the top of the group fills. In order for it to work, there has to be space between the top of the puck and the shower screen. Some machines use water line pressure and delay the pump for a few seconds, others pulse the pump. The manual E61 has a spring loaded cylinder that ramps the pressure; the automatic E61 has a cavity so that the gicleur isn't dependent on the heapspace over the puck. Lever machines are the simplest and most flexible, since one can let the water soak into the puck as long as one likes before engaging the lever
I have read through the material on the Andreja Premium (Instructions and on HB Quick Mill Andreja Premium Espresso Machine Review ), and there is something that has been puzzling me about the lever that turns on the pump. I suppose this is not peculiar to the Andreja, but all machines like this one. There is a half-way stopping point when one pulls up the lever that does not seem to engage the pump or push significantly on the black (spring?) button. Does this or could it have anything to do with a kind of manual preinfusion? I figure that this half-way stopping point has got to be there for some reason, and again, just wondering now if it has anything to do with preinfusion. (If I have missed a thread on this, however, just let me know!)

Thanks

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cafeIKE

#8: Post by cafeIKE »

Care to add "with the same equipment"?

There is a dramatic taste difference between 30ml in 30s from pump on [30ml in ~22s] and 30ml in 30s from first drop.

Rather like listening to a Cockney and a Jordie. They're both speaking English, but there's no mistaking one for the other.

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HB
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#9: Post by HB »

cafeIKE wrote:Care to add "with the same equipment"?
OK. I think it goes without saying for informed readers that all espresso machines are not created equal, but it doesn't hurt to mention it for the benefit of less experienced baristas.
Anthony wrote:There is a half-way stopping point when one pulls up the lever that does not seem to engage the pump or push significantly on the black (spring?) button. Does this or could it have anything to do with a kind of manual preinfusion?
From the FAQs and Favorites Digest, see Is there a purpose for the E61 middle brew lever position? and Can anyone explain preinfusion on the E61?
Dan Kehn

Anthony

#10: Post by Anthony »

That's it! Thanks.