I don't know if this should go in Tips and Techniques or here, but since my ultimate question is buying advice (if to buy at all), I'll post it here.

So here's my set-up. I have an Alex Duetto II, a Rocky Doserless grinder, and a Rattleware 58mm flat tamper. (I know, there are those that might opine that I should have upgraded my grinder before upgrading my Gaggia Twin, but the Gaggia stopped functioning, and regardless, I love that Duetto on my counter, playing with it every morning, and the results it gifts to my mug after I'm done playing--and besides, I love my Rocky which through no fault of its own, continues to function flawlessly).

While I used to practice the 30 lb. tamp on a scale, lately I've been doing something different. I'm grinding finer, and tamping a little bit longer, but with less pressure. I first let the weight of just the tamper compress the grounds till they are flat, then I start spinning the tamper clockwise (with maybe just a few pounds of pressure) until I feel the texture of the grounds change and begin to "grip" a little bit--you can feel the slight vibration through the tamper). Then I let 'er fly. I find I'm getting fuller more heavily extracted shots, and when tested in my bottomless portafilter, I'm getting 'evener' extractions. My pucks are no longer suitable for the hockey rink, and I usually have to wipe/rinse the basket to remove some stragglers after the shot--the puck comes out as one piece, but it is wetter than the pucks tamped with a standard 30 lb. technique. I like the results I'm getting in the cup.

Now, so here's my question: Should I get a convex or serrated tamper? I would think a serrated tamper might create more initial surface area--perhaps just at the top of the puck--but I would think that a convex tamper might also create more surface area throughout the entire puck--the surface of a 3 dimensional sphere is greater than the surface of a two dimensional disc. I'm also asking from a technique and results standpoint, not whether I'd enjoy buying and owning different tampers, because I certainly would. What do y'all think??

I have a flat and convex tamper but I've found no noticeable difference between the two. I suspect it would be the same case here too. The effect of tamper's surface wouldn't have any noticeable effect to most people, as long as you distribute evenly and tamp level; which couldn't be fixed even with the best tamper(if there is one).

In my opinion, you are putting way too much importance on the tamper. Just be consistent and make sure you tamp level.

I agree with Steve, though according to this poll, opinion is split. I voted "Not very important". The consistency of the tamp does matter, but I weighted it lower because the difficulty of mastering tamping technique is the lowest rung on the ladder of essential barista skills. The shape of the piston? Eh, I prefer convex since it's less disruptive if the tamp is slightly canted.

same. I use a flat tamper. I wanted a convex tamper, but after realizing my inconsistency is probably just me, I practiced and now get perfect shots with the flat tamper. I don't focus too much on it. As long as it is level and provides enough headroom for the dispersion screen. I emulate the baristas at my favorite cafes. They all use flat tampers, level, firm (not necessarily a precise amount of pressure), polishing twist, all done in 3 seconds. However I did notice less care was needed in distribution and tamping when I went from the hand mill to the mazzer mini and further less from the mini to the super jolly. I have been pleased with this, as I don't think it should take 10 minutes or even 5 minutes to build an amazing shot. no WDT, no fancy tamper moves. Moral of story: save your $30-$80 and put it toward your grinder upgrade fund! You do have one of those, right?

EDIT: Dan you do make a good point about the surface disruption from a canted tamp. I never thought how the spherical surface of a convex tamper might make a smaller impact on the levelness of the puck! Cool concept.

HB wrote:The shape of the piston? Eh, I prefer convex since it's less disruptive if the tamp is slightly canted.

shame on you, Dan

cafeIKE wrote:"In theory, there is no difference between theory and practice. But, in practice, there is." - Yogi Berra

A tamper with 1mm rocker has a 421mm face radius. The face circumference is 2.645 METERS.

If you tilt a 58mm tamper 3.945° you will raise one side 1mm and lower the other 1mm about the center of the face, for a 2mm differential in your puck. It makes no difference whether the tamper is flat or concave. A BALL tamper with a 58mm diameter could be rotated any which way for a constant, probably crappy, tamp.

Additionally, if the force is directly on the handle axis, and assuming an even initial distribution, the low side will compress / displace the coffee more.

Tilt is tilt. Flat, convex, ribbed, concave, dodecahedron...

ah yes, Ian, thanks for that description. Looks like I need myself another shot! I was indeed thinking of the effect a tamper with a convex face of equal spherical diameter to the basket would have when tilted. nice call! However, in ideal world land, if the basket sides were imaginary, and the tamper was at least several mm larger than the puck...

I know it doesn't pass muster with Ian's calculations, but convex pistons seem more forgiving to me. Maybe it's how the compaction forces are distributed among the coffee particles because of the angle? Honestly, I don't have (or care about) a mathematical explanation. Don't take my word for it; try one and decide for yourself.

HB wrote:... I prefer convex since it's less disruptive if the tamp is slightly canted.

He never said the things you said he said.

"...less disruptive..." in theory true then, though perhaps, Ike, in practice "...slightly less disruptive..." tending toward "... very, very, very slightly less disruptive."

... or maybe then "...slightly less disruptive seeming."

Seems fair enough.