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.

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

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

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!

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.

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

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.

ojaw wrote: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 :)

I don't want to sacrifice the clearance. My scale and 6oz cup (I mostly have long blacks) barely fits without the mat. I don't mind scuffs. It makes the Robot look well loved. The mat is still handy for storing the tamper and PF.

Paul_Pratt wrote: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.

These tampers look amazing! Will they fit into the robot's hand the way the current one does?