Inconsistency of dose and yield

#1: Post by **BIKERBOB** » November 22nd, 2021, 10:12 am

Good Day Gents and Ladies
I have a Breville dual boiler machine. First brief history each morning I prepare a cup for my wife and myself; and recently have been documenting Dose and Yield (results below in grms)

Cup    1    2   3   4    5    6    7    8
-----------------------------------------
Dose   17  17  17  17   17   17   17   19  
Yield  29  37  38  43   39   54   39   48

Odd number cups are poured first followed by even number cup
To my thinking both odd and even numbered cups should be equal within reason; as can be seen the even numbered cups or second cup has a larger yield. Any suggestion has to what is happening?
thanks
Bikerbob

#2: Post by **Jeff** » November 22nd, 2021, 10:58 am

I'm guessing you're stopping with time, yes?

My first guesses are:

* Stale grinds in the grinder
* Temperature not yet stable

#3: Post by **ojt** » November 22nd, 2021, 11:44 am

I agree it would sound like a temperature issue. In case of stale grounds the first one should be faster flowing, no? Wild guess: do you thwack the PF empty, clean under cold water, dry, prep and then pull the second shot? In this case the portafilter might be colder for the second shot?

#4: Post by **Peppersass** » November 22nd, 2021, 4:28 pm

A common cause of this is a varying level of beans in the grinder hopper. More beans, more weight, finer grind, slower shot. Fewer beans, less weight, coarser grind, faster shot. Depending on the grinder, you may need to keep a minimum or constant level of beans in the grinder to get a consistent grind.

Does that correlate with your yield measurements?

Other causes of inconsistent grind are misalignment of the burrs, loose parts, worn out parts, etc.

November 22nd, 2021, 4:32 pm

Thank you for the reply
Age of coffee is unknown as purchased at a bulk store
You are correct yield is auto stopped at 30 secs
As to temperature; machine is set to start a 7:45; First cup is about 8:00 Temp at 200
Bikerbob

November 22nd, 2021, 5:44 pm

Hi Robert,

Time to begin brew on this machine is okay.

You mentioned weight in the PF in grams, but are you using a scale that weighs in tenth of a gram? If not, your weight could be anywhere from 16.5g to 17.4g and still show 17g.

Also stale beans can accentuate puck prep problems, so maybe you can tell us how you prep your puck.

Last thing I'm mentioned is the 920XL is a highly repeatable machine shot to shot, but just to check out your machine, run a water debt control 3 to 4 times without the PF in the group, collecting the water in a measuring cup (or the like) on a scale for the shot duration (30 seconds). When I do this (once a month), my values never differ by more than 2 to 3g (180g +/- 3g).

Hope that helps!

November 24th, 2021, 9:58 am

BaristaBob wrote:Hi Robert,

Time to begin brew on this machine is okay.

You mentioned weight in the PF in grams, but are you using a scale that weighs in tenth of a gram? If not, your weight could be anywhere from 16.5g to 17.4g and still show 17g.
My scale only measures whole number

Also stale beans can accentuate puck prep problems, so maybe you can tell us how you prep your puck.
Nothing special grind for 14 secs; pour into porter filter; give good shake to settle the grounds; tamp with preset tamper ( approx 30lbs) into machine

Last thing I'm mentioned is the 920XL is a highly repeatable machine shot to shot, but just to check out your machine, run a water debt control 3 to 4 times without the PF in the group, collecting the water in a measuring cup (or the like) on a scale for the shot duration (30 seconds). When I do this (once a month), my values never differ by more than 2 to 3g (180g +/- 3g).
Repeatable seem reasonable I get and average of 202g after 30 secs
What I have noticed is that after doing the above test twice; is that the yield is more consistent
Will do more tests where I will pull a dumby prior to pulling the shot

Hope that helps!

Thank you for your consideration
Bikerbob