Flat versus curved bottom tamper

Beginner and pro baristas share tips and tricks.

Postby Orcasite » Jul 11, 2018, 9:20 pm

I thought I would post a recent experience that I found instructive: I updated my 12-year old Quickmill Andreja shower screen and basket with the latest and most recommended ones in the hopes that I would get better espresso (and an espressso flow without spurters) from my bottomless portafilter. That simply didn't happen and I was at a loss as to understand why. My puck preparation was as careful and thorough as I could make it. Then I realized that the new basket was flat-bottomed, while my old one was rounded and the tamper that I was using was also rounded in the theory that - with the round-bottomed basket - they presented an even puck density to the water pressure. With the new flat-bottomed basket and screen and the round-bottomed tamper, the flow would start off in the middle, enlarge from the center and after reaching the circumference of the basket's holes, start spurting like crazy from the center area.

After watching this a few times and experimenting with slightly different methods of puck preparation - none of which helped, I pulled a shot using my standard puck preparation methods but tamping with my very first (and previously retired) no-name flat-bottomed tamper. Voila! ("Wah-la" in English). The result: a perfect video-ready single-cone of beautiful espresso, tiger-striped and delicious; not a single drop of espresso on the lip of the cup, the machine, counter or the floor. And I have repeated that experience daily now for a few weeks. What a simple solution...

Does this experience sound familiar to anyone?

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Postby RapidCoffee » Jul 11, 2018, 11:35 pm

Not to me. My baskets all have flat bottoms, and both convex and flat tampers work fine. If anything, it is slightly easier to get a "pretty" bottomless pour with a convex tamper.


Postby lagoon » Jul 11, 2018, 11:36 pm

Probably a lot of variables in play. I get marginally more consistent results with a convex tamper.


Postby erik82 » Jul 12, 2018, 1:56 am

I seemed to get a bit better extraction with convex for a while but in the end flat seemed to work better. I did like the C-flat/C-ripple from Reg Barber the most (convex outer part and flat inner part).


Postby JayBeck » Jul 12, 2018, 10:45 am

I have an Espro Convex and LevTamp Flat. I think if using the VST baskets, a large modern flat based tamper like a LevTamp probably works best. If using stock or EPHQ baskets, I think Convex is probably equally good and more forgiving.

I actually read some 10+ year old threads here where everyone was raving on Convex over Flat at the time. Now the consensus seems to be Flat over Convex. I think it's flavor of the month type stuff. But on VST, having a slightly larger tamper does seem to help since those baskets are just different altogether. And it is rare to find a convex tamper bigger than 58mm whereas flat tampers are easily found at 58.35-58.50 size.

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Postby ira » Jul 12, 2018, 2:48 pm

Grinders have gotten better as has our understanding of the goals so the changes in preferred tamper shapes might be for real reasons. Also we now use 58.5 flats instead of 58 flats and 58 curved might make up for the deficiencies of 58 flats that are also solved by 58.5 flats. Not claiming to know anything, but so much has change in that time that thinking it's "flavor of the month" might not be correct.



Postby JayBeck » replying to ira » Jul 12, 2018, 2:58 pm

Denis has a comment on Kafatek's website: "We also noticed that flat tamper base extracts slightly better than convex base. Again, we don't know why this is, its just something we observed. While convex base makes it easier to create better looking bottomless portafilter extractions, the extraction yield is about 0.2%-1% less than flat based tamper."

I think we all respect Denis well enough that we can take this comment as a great summary. Convex is easier to use; Flat, when mastered, can get slightly higher extraction.

Me calling it 'flavor of the month' is basically: While we can measure this, can we taste it? I understand why Flat's are more common now, especially with trying to extract as much as possible since this is a hobby for us. It's interesting,IMO, that La Marzocco ships convex tampers still with their machines.


Postby trapperkeeper » Jul 12, 2018, 3:10 pm

match the basket and tamp - flat basket/flat tamp, convex basket convex tamp - keeps the puck depth consistent and more uniform extraction. Whether this results in better flavor is another question.
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Postby samuellaw178 » Jul 12, 2018, 5:47 pm

trapperkeeper wrote:match the basket and tamp - flat basket/flat tamp, convex basket convex tamp - keeps the puck depth consistent and more uniform extraction.

Worth noting the 'convex' basket is probably a result of many pulls.. :P My VST basket started as perfectly flat when new but now it has developed a slight curve. Happened with other baskets as well.


Postby trapperkeeper » replying to samuellaw178 » Jul 12, 2018, 8:14 pm

Interesting! maybe a little aggressive with the tamp pressure? I dunno I pretty much only use the convex IMS baskets... matches the euro curve on my Torr Tamp.. :D
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