Dwell time: Can someone explain? - Page 2

Beginner and pro baristas share tips and tricks for making espresso.
tr182md

#11: Post by tr182md »

I have a 5 second pre infusion at line pressure programmed in and I start the timer when the pump kicks on. I don't see any espresso during pre-infusion. I suppose I could increase that until I see espresso.

On my machine, a Vivaldi the screen sticks out a ways and when I started weighing my shots recently I went back to bottomless portafilter. I noticed my usual method was touching the screen. Trying to get a nice bottomless shot without channeling and not touching the screen I had to really decrease my normal dose. I got it dialed in again but my dose is down to almost 16g.

Today I used triple basket and was able to pull a nice 20gram shot at 1:2 and it was delicious.

My old way was just to dose coffee into basket until full, tap it once, level it with finger which is a little convex and tamp. My goal being to have coffee tamped enough to be just below ridge. Weighing has been more consistent.

User avatar
another_jim
Team HB

#12: Post by another_jim »

SonVolt wrote:Ahhh ok - so, these instructions are essentially to determine the lower and upper bound limits of my grinder from strong to light coffee extremes? Once I have that figured out any coffee I buy should fall somewhere between those grams/grinder settings?
That's correct. 12 to 16 grams will work with most of the stock double baskets delivered with pump machines like the Gaggias, Silvia or Bezzeras. For an E61 machine and baskets, go with about 13.5 to 17.5 This is also true with the older style LM baskets. With VST or Strada baskets, this exercise is somewhat pointless -- they are mandatory fine grind baskets and can't be varied a lot on dose.

Here's an exhaustive look at dose ranges. Here's a shorter one on the same subject
Jim Schulman

User avatar
boar_d_laze

#13: Post by boar_d_laze »

another_jim wrote:For an E61 machine and baskets, go with about 13.5 to 17.5. This is also true with the older style LM baskets.
My range is about 1g heavier than Jim's. That doesn't make me right and him wrong. It's just an observation borne from personal experience. Jim seems to like lower doses more than I do, maybe that's it. He's also probably pulled a zillion more E61 shots.
With VST or Strada baskets, this exercise is somewhat pointless -- they are mandatory fine grind baskets and can't be varied a lot on dose.
+1. Both brands come with nominal dose sizes, and won't do well with much variation. Watch out for the Strada "17g Double" though, it's the same size as the VST 18g basket. In my machine, the acceptable dose range for each was 17.5g - 19g. 17g left too much headroom; appropriate flow times/rates would over extract.

For whatever reason, IMS baskets, as precisely manufactured as Strada/VST, are more tolerant to dose variation. They also flow faster, which means -- everything else being equal -- a slightly tighter grind or heavier dose. I'm using a nominal 16g - 22g, Cimbali specific basket, and -- with my C+/FC roasts -- it's good from 17g - 21g. I used to dose my Stradas 18g - 18.5g, and am now dosing my IMS baskets 1g heavier. Same brew ratios though.

I don't know about the very popular, more reasonably priced (also "precision") HQ baskets Espresso Parts sells.

Rich
Drop a nickel in the pot Joe. Takin' it slow. Waiter, waiter, percolator

User avatar
another_jim
Team HB

#14: Post by another_jim »

Yeah; I tend to grind a little finer and dose a little lower than most people.
Jim Schulman

Gig103

#15: Post by Gig103 »

I have a dwell time question too, hope I can join in on this existing thread!

My Andreja Premium takes about 7 seconds from pump turn on, to 9-bar (with a blank). When brewing, that makes it closer to 10 seconds before the first drip. Is that a "10 second" dwell, or a "3 second" dwell?
https://youtu.be/XDGaec-5RWo

User avatar
canuckcoffeeguy

#16: Post by canuckcoffeeguy »

Gig103 wrote:I have a dwell time question too, hope I can join in on this existing thread!

My Andreja Premium takes about 7 seconds from pump turn on, to 9-bar (with a blank). When brewing, that makes it closer to 10 seconds before the first drip. Is that a "10 second" dwell, or a "3 second" dwell?
https://youtu.be/XDGaec-5RWo
This is normal for an E-61 machine with a vibe pump. E-61 groups, by design, have a pre-infusion chamber which needs to fill before reaching full pressure. And a vibe pump has a slower ramp-up to full pressure as compared to a rotary pump.

My E-61 HX has a vibe pump and behaves similarly. However, I don't know if you would call this delay period "dwell" or "pre-infusion" time. I suspect this would result in an endless debate stretching hundreds of pages.

For this reason, I count my shot times from first drip, not from pump activation.

Gig103

#17: Post by Gig103 replying to canuckcoffeeguy »

Thanks for explaining - seems like consistency is the name of the game; if I like the shot, I can time it however I like! 8)
But this 'pre-infusion' chamber, I understand how it works for a rotary with line pressure, but does that mean that the water is seeping into the puck even though I have a vibe pump during that time?

User avatar
canuckcoffeeguy

#18: Post by canuckcoffeeguy »

Gig103 wrote:But this 'pre-infusion' chamber, I understand how it works for a rotary with line pressure, but does that mean that the water is seeping into the puck even though I have a vibe pump during that time?
Well, now you're getting into controversial territory. Or, at least territory which causes much confusion and some disagreement.

The line pressure vs passive pre-infusion comparison (and people can't agree on whether this should be called passive pre-infusion) is a different issue altogether. It is related to the E-61 design, but different from the inherent "dwell" time or delay that precedes an E-61 shot. A plumbed in E61 will generate line pressure pre-infuision, whereas a reservoir only E-61, in most cases, is capable of boiler pressure pre-infusion. Again, regarding the latter, there is disagreement about what to call this. In either case, this is different from the "dwell" time you were asking about.

Check this link:
E61 preinfusion for plumbed and reservoir-only models

I'll leave it up to more knowledgeable people than myself to comment.

Gig103

#19: Post by Gig103 »

I will follow up in other threads and not derail here. Thanks for the info on the dwell time.

User avatar
boar_d_laze

#20: Post by boar_d_laze replying to Gig103 »

It's not a derailment.

The E61 group has a few chambers inside the head. The chambers are connected by channels with spring loaded valves. When there's enough pressure from the pump the valves open, and the water flows into the group at pump pressure (limited by an OPV, with vibe pumps).

However, before the system goes to full pressure there's a period of low pressure preinfusion. It only lasts a couple of seconds, allows a fairly small amount of water; and the pressure is not constant, but ramps up. Compared to line pressure pre-infusion, E61 preinfusion is very gentle until it isn't.

If your puck is well constructed, any preinfusion period is (at least part of) dwell time. If coffee's coming out of the pf, the puck is "infused," and there's no pre-anything.

That leads to the question, "is all dwell time preinfusion?" As long as your puck is well constructed, it's trivial. Long dwell times at full pressure indicate a grind/dose problem.

The concept of dwell time is useful in terms of establishing and recognizing normative flow rates, shot times, etc., and as a diagnostic for grind/dose. If I'm not mistaken it was coined by Jim (Another Jim). The idea of scoring each second of dwell time as half a second of total shot time is also Jim's, and as useful as you want to make it.

By way of counter example:
  • My espresso machine has a built-in 4 second, line pressure pre-infusion period. Afterwards, the rotary pump starts and nearly instantaneously ramps to 9 bar. I expect the first drops of espress to appear when the pump starts or very shortly thereafter. If it starts before, the puck is channeling or the coffee is old. If it takes too long, the grind is too fine and/or dose too high.
  • I do time my shots (often enough to keep me honest regarding correct grind and dose), but don't start my stopwatch until the pump starts.
The point is, there's no special juju. Just understand what the shot is telling you in whatever ways best suit you and your equipment.

The discussion about "passive preinfusion" ended with a realization by all involved parties that "passive" is hopelessly ambiguous and adds nothing to understanding.

Rich
Drop a nickel in the pot Joe. Takin' it slow. Waiter, waiter, percolator