Dwell time: Can someone explain?

[SonVolt]

I'm following this guide to help fine tune my new espresso machine. I'm a little confused on what dwell time means, especially the "50%" part. Can someone help explain this?

1. Adjust the grind until you get a shot that weighs 20 to 25 grams in 30 seconds. (when timing the shot count the dwell time, the time between turning on the pump and seeing the first drop, at 50%)

[cmin]

They mean, like if you turn on the pump and don't see first drips till say 6 seconds, count that as 3 vs 6 into your total time. Various ways, personally I time from first drip, after preinfusion and dwell drips start around 7-10 seconds and since my machine has a shot clock I stop it at 37-40 seconds.

[HB]

To further elaborate, I believe Jim suggested using half the dwell time as a simple way of "normalizing" extract timing comparisons between espresso machines with short and long dwell times. For example, commercial espresso machines like the La Marzocco Linea have very short dwell times (~3-4 seconds) while espresso machines with E61 groups have long dwell times (~6-8 seconds). By halving the dwell time, it saves everyone the trouble of qualifying extraction times by what espresso machine is used while still allowing for fairly reasonable comparisons.

[another_jim]

It's a rule of thumb for learning how to pull shots and get into the right zone; and it works reasonably well for most pump machines.

However, I do not know how to compare shot times when dealing with variable pressure machines, either levers or pressure profiling pumps -- these can have very long shot times, up to a minute in some cases.

The best technique as always is to tune your parameters by taste; and if you are not confident about your taste, to fake that confidence until you have it. But for those who crave something more definitive, timing shots in this way will work.

[SonVolt (original poster)]

Thanks. I had some improvement today in my espresso quality, especially taming the intense sourness. Today I reached "Nespresso" quality, which isn't saying much, but it's 100% better than what I was pulling a few days ago.

Curious - the guide starts with only 12 grams in a double portafilter. Once I get it dialed in at 12 grams do I stay at 12 grams indefinitely or up it to ~17 which seems to the be norm?

[cmin]

I would dose higher but that's me, can barely tamp 14g in my double, 12g wouldn't work. Personally I'm always between 16 and 18 grams. Seems to be the sweet spot for damn near any bean or blend I've used over the years and you'll see majority of others in that range save for ones using triple baskets dosed higher. The dosing in that article is pry meant as an example like dialing in at X grams.

[SonVolt (original poster)]

Should I not be taking "12 grams" literally then? Can anyone explain why the article/tutorial uses 12 grams as its starting point if 12 grams isn't the typical amount for a double?

[Bikeminded]

I'm using 18g in the 700 double basket.

[jfrescki]

Should I not be taking "12 grams" literally then? Can anyone explain why the article/tutorial uses 12 grams as its starting point if 12 grams isn't the typical amount for a double?

From the next bullet, Jim is suggesting this is specificially:

•This is you finest grind setting, suitable for light roasts, very acidic coffees, or otherwise very powerful tasting coffees

You'll notice he then says move to 16 grams, which is the upper end of normal to be used for bland coffees. YMMV. Unless you have an extreme coffee (powerful or bland), you'll probably want to dose at least 14g or more.

[SonVolt (original poster)]

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?