When should you start timing the shot? When you turn on the water switch, or when the espresso starts to flow? Why? Does it depend on the type of machine you have?

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There is a debate in the Coffee Community as to when to time one's shot. But in the final analysis they are close to the same results. Some believe that timing the shot should begin during the pre infusion state, and end on the last drop of espresso. Others, myself included like to time their shots from the first drop of espresso exctraction, until the last drop.

The time of pre infusion takes approximately 5 seconds, so when the time includes pre unfusion, the pour rate will be about 5 more seconds longer than if you were counting from pure extraction. So you may call your shot a 30 second pour by counting pre infusion stage, I will get about 5 seconds less on my count, or about 25 seconds per shot for my pour, or extractopn rate.

So you see, we are both using about the same time but different terminology as to when to begin the count!
Well said, Andrew.

Andrew Hetzel said:
So long as it's a good evenly extracted shot with balanced flavor, the time does not really matter. Even if training for competition, the WBC score sheets deduct only a minimal point value for extractions outside of the so-called ideal 20 - 30 seconds; by contrast, taste is much more heavily weighted.

At your business or in a competition, tasting good is far more important that being within some theoretical time parameters.

Focus on the flavor first; if that's off balance, then go back to review the technical standards like timing.
I agree partially with Andrew... the 20-30 second range is a good starting point, but part of dialing in your espresso is narrowing this down to a better (read narrower target). That said, once you've established that target, consistency between baristas on your bar staff is important.

I personally start timing when the first drops fall from the spouts, but have no valid reason for doing this.
Time, pressure, amount of espresso and temperature are all variables you can't live by numbers go with opinion change things see how it effects the coffee even if it's bad and out of a range considered " to spec" it gives you a better knowledge of what to look for in a shot. think if you have a clover you don't want all coffee's brewed at the same temp different roast taste better with TRIAL AND ERROR.

Brady said:
I agree partially with Andrew... the 20-30 second range is a good starting point, but part of dialing in your espresso is narrowing this down to a better (read narrower target). That said, once you've established that target, consistency between baristas on your bar staff is important. I personally start timing when the first drops fall from the spouts, but have no valid reason for doing this.
One thing that I have never found a "definitive" answer for is the time for a dopio. I am assuming that using a double basket, I should be looking for times between 40-50 sec?
You should always be shooting for 25ish seconds, regardless of whether you are using a single or a double or a triple basket, whether you are pulling a ristretto or a lungo. It has to do with volume, not time.

-bry

Chris Hooton said:
One thing that I have never found a "definitive" answer for is the time for a dopio. I am assuming that using a double basket, I should be looking for times between 40-50 sec?
Bry,

I think I am getting my head around what you are saying. So long as the volume of the finished cup and the mass of the ground coffee increase proportionally then the time stays the same. So it could be expressed something like this:


Where d is the mass of the ground coffee in grams, V is the volume of water in ml and the time of the shot in seconds and R some crazy constant representing the rate of extraction.

in the case of a single shot it might look something like this.


I say something like this because according to Andrea Illy in Espresso Coffee the real model is something like this:

I dropped math at functions statistics and trig my senior year to take Spanish four so the calculus here is a bit beyond me. Illy says that p represents the difference in pressure above and below the puck, R is the hydraulic resistance of the cake, V is the volume of the beverage, T is the temp inside the cake, and t is the percolation time (I'm not sure if that is the full extraction time of the time to first drop). Illy doesn't define the d at the end of the expression, but I assume it is the mass of the cake, because it would have to figure in there somehow right?

This problem kept me up last night, which caused my wife to comment that I am a geek. I wonder what the correlation between the Illy's equation and my crude expression may be. Perhaps some more mathematically inclined out there can shed some light on the subject for me. I tried to rearrange Illy's equation a little and found this:

and

which appeared in my expression.
Any thoughts?

Bryan Wray said:
You should always be shooting for 25ish seconds, regardless of whether you are using a single or a double or a triple basket, whether you are pulling a ristretto or a lungo. It has to do with volume, not time.
-bry Chris Hooton said:
One thing that I have never found a "definitive" answer for is the time for a dopio. I am assuming that using a double basket, I should be looking for times between 40-50 sec?
I start timing my shots the moment I start the pressure, that time that the water is in the coffee is relevant. If you are truly going to measure and time shots, the time before you see the espresso is just as important as the time after.

As long as your machine is pumping at 9 bars, it is really irrelevant what make or model it is. Unless you got a trick slayer (or whatever else) and are doing all sorts of cool things that I haven't been able to yet... :(
Chris Hooton geeked out with lots of equations that I'm not going to fully repeat:
Bry,
I think I am getting my head around what you are saying. So long as the volume of the finished cup and the mass of the ground coffee increase proportionally then the time stays the same. So it could be expressed something like this:


Where d is the mass of the ground coffee in grams, V is the volume of water in ml and the time of the shot in seconds and R some crazy constant representing the rate of extraction.

(snip)

A couple of thoughts here, aside from the observation that your post made my head hurt.

1. As a side note, it is my understanding that the more accurate way to look at extraction ratios and the equations that govern them is to use weight of both the ground espresso and the finished shot. This takes variation in volume due to variations in crema amount out of the equation.

2. If I recall my calculus correctly, Illy's model does not look like it include mass of espresso directly. The dt that appears at the end is calculus for "derivative of time", hence the use of italics. As I read it, all the equation does is to show that the volume of beverage collected depends on the pressure gradient and hydraulic resistance, recognizing that those vary over time and temperature. Where mass comes into play is in hydraulic resistance (which is also dependant on other things, ground size, ground structure, etc.)

3. That being said, Illy's equation looks to me like just a fluid-flow model which describes how much water flows through the cake in a given time. It does not cover extraction, as it doesn't care if your basket is full of espresso or sand. So this equation is part of the answer, but not the whole answer.

4. What I think you might be looking for is some sort of extraction-rate model. I don't have one handy, but have some thoughts on what one might look like. Put simply, I think it would say that as long as you used an appropriate amount of ground espresso for the volume of beverage you wanted to produce AND the grounds were in contact with their water for an appropriate amount of time, you will get a good extraction. That last part seems like the bit that we care about for this discussion... you don't want the water in contact with the espresso for too little time or for too much time.

SO...

5. Since contact with water is key, I think you should expect optimal times for single, double, and triple baskets to be closer together rather than being directly proportional to the amount of espresso used. Which I think is what you said before you started quoting Illy.

THANKS Chris, now my brain hurts! BUT this little thought experiment has helped me get my head around something that has been a bit of a cloudy area for me, so really thanks. Looking forward to other thoughts on this as well.
Thanks Brady, that helps make sense of this for me.
All this doesn'tr seem to take in account tempature, which changes everything...Unless that is included in the constant?
Chris Hooton said:
Thanks Brady, that helps make sense of this for me.

Good. Like I said, this is something that I've been pondering as well, so it was good to dig in a little and think about it.

As far as your initial statement regarding timing for a doppio... I think its fair to say that every reference you've ever seen here to shot timing has been referring to extraction using a "double" basket. I realize that's not definitive, but it does say something.

Mike, if I understand the equation correctly, Illy captured temperature as a contribution to hydraulic resistance. We should obviously also consider its contribution to the extraction process.

For the record, I have changed my stance on timing since my post last November. I now start timing when I hit the button. FWIW, isn't this is how the timing works on La Marzocco machines with Chronos pads/timers?

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