Cafelat Robot dark ring in the puck

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phildawes
Posts: 10
Joined: 1 year ago

#1: Post by phildawes »

Hello! I have a Cafelat Robot and I love it (and love the shots I'm able to get from it), but I always get a thin dark ring of under-extraction at the base of my pucks.

My routine is:
- 17.5g in, 35g out
- DF64 with aligned SSP MP burrs, wdt
- paper filter under the metal screen
- pre heat everything (piston, double pour basket)
- pre-infuse 10 seconds, 9 bar pressure to start, ~6 bars mostly, less towards end
- whole thing around 40-50 seconds

I've tried varying a bunch of things, but always get the dark ring
- various coffees, levels of roast
- various levels of pre-infuse, time and pressure
- punched filter paper at the bottom (filter paper sandwich)

The only thing that doesn't result in a dark ring for me is a large 22g dose more coarsely ground and a 1:3 turbo style. This results in a perfect looking puck to my eyes.

I enjoy a traditional 1:2 style shot, and the shots I'm able to get from the robot are delicious. Are other people getting this ring?

Thanks!

Phil

Miltonedgebert
Posts: 94
Joined: 2 years ago

#2: Post by Miltonedgebert »

I'm pretty sure the ring is just an artifact of the tapered basket. I ignore it because if the coffee tastes good, the coffee tastes good.

jpender
Posts: 3917
Joined: 12 years ago

#3: Post by jpender »

Can you post a photo?

I've never noticed a ring but I also don't examine the spent puck very often. I looked just a minute ago and the puck (from a darker roast) was uniformly dark.

phildawes (original poster)
Posts: 10
Joined: 1 year ago

#4: Post by phildawes (original poster) »

Here's a recent picture i took

jedovaty
Posts: 537
Joined: 13 years ago

#5: Post by jedovaty »

Have you tried a longer pre-infusion or paper at the bottom?

vit
Posts: 996
Joined: 9 years ago

#6: Post by vit »

How does the flow start ? Evenly, in the center or at the edges ?

Are we actually sure that coffee is less extracted in darker parts (I also read that in a few places) ?

buckersss
Supporter ♡
Posts: 578
Joined: 3 years ago

#7: Post by buckersss »

I may certainly be wrong, but if you have less coffee around the edge of the puck, perhaps the extraction will be more uniform?

If this is the case you could try nutation style tamping, which I believe should leave you with a more convex looking puck if examined from the side. I believe there are some older posts by Jim on this.

phildawes (original poster)
Posts: 10
Joined: 1 year ago

#8: Post by phildawes (original poster) »

[quote="vit"]How does the flow start ? Evenly, in the center or at the edges ?

Usually flow starts fairly evenly. Occasionally it starts as a ring at the edge, mainly if I try to make a hill when wdt-ing to increase the amount of coffee in the center of the puck. Both result in a similar looking puck at the end though.

phildawes (original poster)
Posts: 10
Joined: 1 year ago

#9: Post by phildawes (original poster) »

buckersss wrote:I may certainly be wrong, but if you have less coffee around the edge of the puck, perhaps the extraction will be more uniform?

If this is the case you could try nutation style tamping, which I believe should leave you with a more convex looking puck if examined from the side. I believe there are some older posts by Jim on this.
Yeah that does sound worth a try thanks. I've experimented a bit with forming a hill in the centre when WDTing but it's not very repeatable.
Unfortunately I have the robot leveling tamper so nutation isn't really an option. Hmm.. Actually I wonder if I can take the plastic leveling bit off...

phildawes (original poster)
Posts: 10
Joined: 1 year ago

#10: Post by phildawes (original poster) »

jedovaty wrote:Have you tried a longer pre-infusion or paper at the bottom?
Yep I've tried both those, thanks. I punched some aeropress papers to fit the bottom with a 45mm punch, but it didn't eliminate the ring.