Cafelat Robot User Experience - Page 210

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vit

#2091: Post by vit »

I faced this question with Flair (classic model), so I'll try sharing some conclusions there and hopefully some of them may be useful for other machines, taking into account specifics of particular machine

Both Flair original and bottomless portafilter are not ideal for getting uniform flow because of uneven distribution of holes, and also, filter area is considerably smaller than basket area. In addition, there is another problem that took my attention after more than a year - bottom is significantly concave and it turned out to be the main problem - especially in bottomless PF which is 2-3x more concave than original PF

Almost always I was getting very nice centered flow, but wasn't really satisfied with the taste. From time to time, I got donut extraction and even dripping from edges of the basket (very likely uneven dosing being the reason) but to big surprise, worse it looked, better the coffee

Finally, I realized the problem - when the puck in concave bottom basket is tamped, density is higher on the edges than in the middle, because it is lower on the edges than in the center so it gets more compressed on the edges. So flow is uneven - most water will go through center part. Tried several methods to make the puck uniformly compressed. Made a convex tamper first, with curvature similar to curvature of the bottom. Contrary to my theory, it didn't help. I realized why - it also pushed the coffee from the center towards the edges and the density in the center was still lower. Working version was tamping with flat tamper first, and doing additional tamp with convex. Other working version was tamping 3-4g of coffee first to get the flat bottom, then dose the rest and tamp (both with flat tamper). Version that was also a kind of working was heaping it in the middle and then tamping without leveling first - but hard to achieve repeatability with this one

Besides by the (better) taste, difference was evident several ways:

- with the same amount of coffee and pressure profile (actually applied force profile), extraction is considerably longer regardless donut extraction I'm getting when tamping this way (flow starts at outer hole row firs, then spreads to the center within 2-3 seconds)
- temperature rise, measured with the probe at the center of the basket bottom is much slower than before, generally reaching maximum during last several seconds of extraction
- color of the crema is much more uniform, without dark tiger stripes
- after extraction, puck isn't considerably softer in the center than on the edges anymore

So it turned out that bottomless PF helped me solving problems that otherwise I wouldn't have :D - but opposite way than expected

Maybe inventor also finally realized this design problem and made a flat bottom normal pattern basket in last iteration of the product, but due to its weight, useless for me as I can't see the way to preheat it to temperatures I need for locally roasted coffee ...

So my bet is - using convex tamper with Robot will most likely cause similar problems like I had with Flair

Final note: trust your taste, not how it looks

jpender

#2092: Post by jpender »

vit wrote:Finally, I realized the problem - when the puck in concave bottom basket is tamped, density is higher on the edges than in the middle, because it is lower on the edges than in the center so it gets more compressed on the edges.
Hi Vit. I've read your post several times and I still don't understand what you're saying here. I would expect the exact opposite of what you are hypothesizing.


I was wondering aloud whether having no holes on the outside ring of the basket would mean higher flow through the outermost holes. But I don't think you answered that or, if you did, I'm too dense to have seen the answer.

It seems like what you did instead was narrate an all-too-common journey of trying this, that, and the other thing until the espresso looks/tastes good. I went from not doing anything except tamping to all sorts of stirring, tapping, and dancing around and chanting spells. With a couple of the coffees I routinely buy I get a nice, even pattern of initial drops and a beautiful flow. But there are a couple of other coffees that *always* have that initial donut, sometimes pretty severely. Nothing I've tried gets rid of it. I haven't lumped the coffee in the middle or used multiple tampers. And the coffee still tastes okay.

It's intriguing to me that the exact same equipment and identical procedure could result in such different pictures because of the choice of coffee.

Charlemagne

#2093: Post by Charlemagne »

The variation must be related to the grind size distribution. We know some coffees produce more fines (looking at you, natural Ethiopians) at the same grind setting. That's going to impact flow, but I'm not sure it means more/less side channeling. I think that some beans are more prone to clumping too. WDT can mitigate that, but perhaps not fully. While these are factors, my guess is that they are minor compared to the basket design.

Jonk

#2094: Post by Jonk »

jpender wrote:It seems like what you did instead was narrate an all-too-common journey of trying this, that, and the other thing until the espresso looks/tastes good.
Speculation is what most of us are able to do. My decision to use a convex tamper was based only on looks, and perhaps you're right that the basket shape might cause an even shot to appear uneven.

I've been pulling back to back shots the last few days and all I can say for sure is that when I'm using the flat tamper there's more initial resistance in the puck. As for flavor it's a draw so far, sometimes one is better than the other and sometimes they're equally good. The difference in yield has been less than 1% so the first try was just a fluke I guess :?

vit

#2095: Post by vit »

jpender wrote:Hi Vit. I've read your post several times and I still don't understand what you're saying here. I would expect the exact opposite of what you are hypothesizing.

I was wondering aloud whether having no holes on the outside ring of the basket would mean higher flow through the outermost holes. But I don't think you answered that or, if you did, I'm too dense to have seen the answer.

It seems like what you did instead was narrate an all-too-common journey of trying this, that, and the other thing until the espresso looks/tastes good. I went from not doing anything except tamping to all sorts of stirring, tapping, and dancing around and chanting spells. With a couple of the coffees I routinely buy I get a nice, even pattern of initial drops and a beautiful flow. But there are a couple of other coffees that *always* have that initial donut, sometimes pretty severely. Nothing I've tried gets rid of it. I haven't lumped the coffee in the middle or used multiple tampers. And the coffee still tastes okay.

It's intriguing to me that the exact same equipment and identical procedure could result in such different pictures because of the choice of coffee.
I actually focused mostly on the question related to convex tamper discussed a few posts earlier and I have a feeling that on Robot or other machines it might cause similar problems like I had with Flair (due to basket shape) and that nice non-donut start of the flow doesn't necessarily prove that extraction is even. I don't claim anything - just wanted to share my experience on the different machine and listed a few things that in my opinion indicate more even flow. There is clear difference in taste - if I tamp "normally", there is lack of typical "coffee notes" but more acid and bitter tones - compared to my reference cafes which serve and sell the same locally roasted coffee. With usual "overdosing" used by most Flair users, this might be less of an issue.

As about outside ring of the holes, Flair classic bottomless basket is also unique because holes on the outside ring are almost twice as dense as in other rings (except 4th from outside that has similar density). Not sure is it good or bad, however flow starts there if I have (according to my theory) about uniformly compressed puck. Hard to say should it be the same with Robot, which has basket with uniform hole distribution (although filter area is also smaller than the basket) so things are obviously different

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Paul_Pratt

#2096: Post by Paul_Pratt »

Image

I have been playing with the tamper samples the past few weeks. They work very well, now we are just working out production, it will probably involve a mold for the delrin part.

With regards the filter basket - I have always preferred those with the tapered bottoms and so we went with this type, also the manufacturer were keen on this as well since it was a very deep draw part and they leaned towards this than a straight up and down shape. They still grumble about it so I am not sure we could get them to do a 2nd style of basket!

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Balthazar_B

#2097: Post by Balthazar_B »

Paul_Pratt wrote: I have been playing with the tamper samples the past few weeks. They work very well, now we are just working out production, it will probably involve a mold for the delrin part.
They look nice, Paul! Looks like being able to keep one in the Robot's "hand" is a no-go, though.
- John

LMWDP # 577

Jonk

#2098: Post by Jonk »

Paul, have you considered an add-on for all the existing, original tampers? (If that's economically feasible. It's nice how other things are modular like the gauge and portafilter.)

I'd also like to say that if you end up redesigning the base plate without the raised part for cups, I for one would consider it an improvement since it would be less fiddly to put the silicone mat in place.

ojaw

#2099: Post by ojaw »

Jonk wrote:I'd also like to say that if you end up redesigning the base plate without the raised part for cups, I for one would consider it an improvement since it would be less fiddly to put the silicone mat in place.
I've foregone the silicone pad; one less thing to clean up and potentially be in the way. I accept the possibility of chips and wear through good use :)

cebseb

#2100: Post by cebseb »

Paul, is there some line I could stand in for the purpose of throwing money at you?

Tamping is one of those actions that still kind of requires me to pay attention during my workflow. Something that I have very little of during the morning shortly after waking up.
Full stop. No half measures. Thankful to be in such a supportive community.