Does the bottom shape of the basket matter?

#1: Post by **tacrita0** » December 20th, 2022, 2:42 am

Hello,

According to the IMS website the bottom shape of the basket matters:

ROUNDED - This specific shape has rounded internal corner that avoids those section where the ground coffee is not well utilized during the extraction. It is not identified by any letter in the filter basket code. Result in cup: more body, more crema, more sugar brownie, and ripe fruit hint. The flavors are more homogeneous.

CONVEX - Cylindrical filters with a Convex bottom that collects coffee towards the center during the extraction, so it's perfect to use with a bottomless portafilter. Result in cup: ripe fruit hint, more acidity and good crema.

FLAT - Cylindrical filters with a Flat bottom that creates a compact coffee pod and improves a lot your extraction. Result in cup: it emphasis the origin of the coffee, the flavor are more distinct, the crema is thin but more silky.

Do you consider that is for marketing only?

#2: Post by **JRising** » December 20th, 2022, 9:56 am

The IMS statements regarding flow characteristics are true. Each one's "Result in cup" characteristics are certainly believed by the ones making the statement. You're welcome to disagree if your palate thinks you should. So I don't think it's "Marketing BS", but it's definitely marketing. Try different baskets, obviously try the flat and convex baskets with your bottomless just to watch the difference. Then you can decide if you can taste the difference.
FWIW: This has been written by someone who very often cannot taste the difference.

#3: Post by **JB90068** » December 20th, 2022, 11:56 am

I am also interested in this. The newest thing on the block is Weber's Unibasket which they say won't flex at all. It also won't produce the single stream that other baskets do and according to them, will offer an even better extraction. I figured I would give it a try and compare it to my VST and IMS baskets.

December 20th, 2022, 1:00 pm

Rounded - which I find similar to slant-sided - medium roasts and darker
Convex (construction, not during extraction) - never used one
Flat - medium roasts and lighter

That's just a guideline made to be broken; I've pulled plenty of darker roasts with a flat bottom, although I always shy away from very light roasts combined with rounded/slant-sided baskets.

YMMV. I can't taste the difference between a flat tamper vs. a C-flat vs. a (mild) convex tamper either.

#5: Post by **cafeIKE** » December 20th, 2022, 3:39 pm

baldheadracing wrote:I can't taste the difference between a flat tamper vs. a C-flat vs. a (mild) convex tamper either.

Pucks here almost never come close to the shower screen and the three faces mentioned above are the final tweak after basket and dose are determined as they each result in a slightly different flow and extraction. YMMV

#6: Post by **daveR1** » December 20th, 2022, 8:36 pm

that deflection formula takes me back to the structures course I took in architecture school. As I recall, it applies to a uniform linear load such as a roof beam. Not sure if it works for the circular (and possibly non-uniform) loading of a portafilter basket. i must be getting too old cause thinking about it makes my head hurt

#7: Post by **jdrobison** » December 21st, 2022, 9:50 am

Think of it as multiple beams all crossing the center of the circle

#8: Post by **daveR1** » December 21st, 2022, 1:13 pm

that's sort of what I was thinking. wondering if there's a formula to analyze it as a circular diaphragm or tensile skin. or to get really weird - Gaudi's funicular model?

#9: Post by **jdrobison** » December 21st, 2022, 3:03 pm

Sure. I think a circle has a different moment of inertia calculation but, otherwise, the bending is derived the same as the beam calc. This is all just academic, of course. The diagram shown still addresses the issue since both are circles.

(It's been years since Structures for me, too. Decades, in fact. I could be wrong

)

December 21st, 2022, 7:34 pm

All the baskets I have that started flat then became curved as I use them.