Third shot consistently pulls a lot faster

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MateoUK
Posts: 7
Joined: 2 months ago

#1: Post by MateoUK »

Hi all,

First post - apologies if I get some of the terminology wrong here when describing the equipment/process. I have a Rocket Appartamento and I seem to be able to pull two consistent shots, but for the third, the shot suddenly comes through a lot faster - without any changes made to the grind (Faustino grinder). From that point on, the shots will keep coming through faster until I change the grind finer to get it to around 25-30 seconds. From then on it will be consistent but the following day, I will need to move the grinder back to it's original setting. I have played around with distribution techniques/tampers, tried different beans, added a thermometer, tried flushing grouphead for longer, even tried backflushing before doing the first shot of the day but it continues this pattern. I clean every day and a more thorough weekly clean.

As an example, today with new beans I pulled three shots, and didn't change the grind at all:
First shot - very slow, 91 seconds
Second shot - very slow, 89 seconds,
Third shot - gushed through, 17 seconds.
I then changed the grinder to a finer setting and had a decent cup at 27 seconds (18g in, 36g out). And if I leave at this setting for tomorrow, it will be far too fine for the first two shots

The difference is so big, I don't think it's related to channeling (if it was, this pattern wouldn't be so consistent for several months).
It's almost as though something is blocking the first two shots but after that it sorts itself out.

Other relevant info:
If I try with no coffee in the portafilter, all the shots seem to come through the same so not to do with flow in this sense.
I don't leave coffee in the grinder, just grind enough for one shot each time so not related to leftover coffee in grinder
Dry portafilter each time in between shots

Any thoughts on why this might be happening? Issue with grinder or espresso machine (or me)? Thanks in advance!

Matt

Jonastheorganist
Posts: 10
Joined: 1 year ago

#2: Post by Jonastheorganist »

Well, since it's not a single dose grinder you need to get the old grounds out every morning. There's somewhere between 1-5 g of retention, grinds that stay in the grinder.
So try to grind for just a few seconds every morning, and all coffee that comes out after that should be fresh, and your shots will hopefully be more consistent.

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Jeff
Team HB
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Joined: 19 years ago

#3: Post by Jeff »

How are you managing the brew temperature?

MateoUK (original poster)
Posts: 7
Joined: 2 months ago

#4: Post by MateoUK (original poster) »

Thanks Jonas - I will give that a go tomorrow to see if it makes a difference. I did think about that but thought if this was the case, you'd imagine the second shot would be different than the first. It seems to only change after pulling two shots (of 18g each).

MateoUK (original poster)
Posts: 7
Joined: 2 months ago

#5: Post by MateoUK (original poster) »

I have added a temperature gauge on to the grouphead. It usually sits at around 100 degrees C and I flush until it's around 94C for the first shot. The temperature fluctuates a little bit but not hugely between the second and third shot which is why I thought maybe not related to temp?

MateoUK (original poster)
Posts: 7
Joined: 2 months ago

#6: Post by MateoUK (original poster) »

Hi all,

An update on this - it looks like the problem is with the grinder. This morning I ground five lots of 18g of coffee on the same setting and put them in a row on the bench. I then put them through the machine in the reverse order and got the opposite pattern that I usually do. The first 2 shots came through quickly, the third was in between, and the final two shots (which were the first 2 to go through the grinder) were extremely slow.

So it looks like the machine is fine and it's an issue with the Faustino grinder. I'm not sure why but it seems to grind the first two or three shots of the day a lot finer than the rest. I will ask about this in the grinder forum to see if anyone knows why or what to do.

Thanks
Matt

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hankbates
Posts: 465
Joined: 13 years ago

#7: Post by hankbates »

I have what I think is a similar issue with my Baratza Sette 270wi, the first two shots are always a little coarser than the second two. Probably slight dimensional change as the heat from the motor and gears spreads through the unit. Different designs will respond differently.
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MateoUK (original poster)
Posts: 7
Joined: 2 months ago

#8: Post by MateoUK (original poster) »

Thanks for this Richard - it's sent me down another avenue looking at heat and grinding. This article here is interesting and could explain what's happening:
https://colonnaandsmalls.wordpress.com/ ... g-puzzles/

I've also found a few others on different forums with similar issues and they all seem to be single dosing (like me) so I wonder if the longer time required to get all the grounds out of the grinder when single dosing causes the grinder to heat up faster than it normally would? I'll try adding more beans in the hopper tomorrow morning to see if it the shorter grinding time makes a difference.