Weird grinder/extraction problem

[kwongheng]

Hi all,

I seem to have a strange issue with this particular bean, but also I have seen the same issue occurring with my grinder before, but these 2 weeks its getting weird. The numbers below are the number of shots that I pulled in succession. I pulled at least 2-3 times on the same grind settings to ensure that the flow rate is not due to technique issue

grinder = Baratza preciso
machine = Expobar Leva (brew 10-11 bars, recommeded by the vendor not to adjust)
Beans = Single origin espresso roast
20 grams in, 40 grams out

1-3: 1D, 29s
4-5: 1B, 25s
6-7: 1C, 21s
8-9: (back to) 1D, 18s!!! (8 bars)
10: (try going very fine) 0I, 18s!!


To explain above, I pulled the first 3 shots at grind setting of 1D at 29s. I then set a finer grind at 1B, pulled 2 shots, but the timing was 25s instead!. Then I went coarser one notch to 1C and it was 21s. When I went back to the original settings at 1D on the 8th pull, it was now timing at 18s instead and the brew pressure dropped to 8 bars. The last try was to go really fine but the timing is 18s instead, probably channeling because I ran out of beans by then.

Anyone seen such results before? Any advise?

[nathanharley]

Out of curiosity, do you do a purge after each grinder adjustment? Or are you single dosing the hopper on the grinder?

Nate

[kwongheng]

I use a single dose but also put some beans in to purge everytime I make an adjustment. Also if you noticed, I pull shots at least two times for each grind size. If the flow is due to left over grinds, then the timing of the first and second shot would be very different, but no, they are both the same each time.

[JojoS]

Particular bean? Can you elaborate? Perhaps the issue is in the roast level of a specific origin.