With all these different tamper styles, it is almost like a conspiracy to keep us buying more and more tampers year after year.

As to C Flat, I still say find a tamper that suits you and get to know how to use it well. The best espressos I have had, the baristas used a flimsy plastic tamper.

If you like convex, the the C Flat has the advantage of standing upright on the counter-top but still being a bit convex.

Tampers are all about ease of use and convenience, not about extraction, in my opinion.

i think the ripple is based on a c-flat then rippled.

i have flat tamper(lava) a convex tamper(espresso parts) a euro curve sort of convex tamper(coffeelab) and a c-flat tamper(reg barber). i use the reg barber because it doesnt give me a blister. at home the coffeelab was fine i liked the adjustable height but the rubber gives me a blister when i use it at the shop almost immediate painful pain. i really love the reg barber c-flat. sometimes i will grab a different one for a few shots and the difference in the cup is not really that great from tamper to tamper. i think dose grind fineness/coarseness and temp have more effect than the shape of the tamper.

i love the reg barber tamper, it was a gift. reg makes a great tamper.

cheers.

jon

RegulatorJohnson wrote:does anyone else think the shape of the group screen would in some way affect what shape tamper to use.

I have heard this argument many times, and it's never made sense to me. When you flip the brew switch, the head space above the puck fills with water, and then brew pressure should apply evenly across the puck surface, regardless of the shape of the shower screen. What am I missing?

I would have to agree with John here. The water is still coming essentially straight down regardless of the shape of the screen.

drdna wrote:If you like convex, the the C Flat has the advantage of standing upright on the counter-top but still being a bit convex.

While it has nothing to do with performance, my budding baristas at home unanimously prefer convex tampers because they spin on the counter better. Like Webbles, convex tampers wobble but they [usually] don't fall down.

a flat screen ->|) <-curved tamper.

a curved screen ->)| <-flat tamper

look at the space in the middle.

there is a difference in negative space between the puck and the screen that is not uniform.

maybe if you dose too much the screen is touching in the middle but not the edge. and the water can get through easier on the edge (donut extraction) or maybe the screen rubs the puck in the middle but not the edge? or just the sides get rubbed by the screen. the cushion of water is not uniform. unless the shapes are similar )) or || this is just speculation as most of espresso theory seems to be. im #justsayin this is about the only thing i can think of that could possibly be a difference or something to make you choose one or the other. or sometimes people say one or the other is more forgiving, etc. maybe it is machine dependent?

something to think about? maybe. a big difference in the cup? maybe not.

this makes me think of the screen on the LM GB/5, it spins. so maybe as the PF locks in the puck may touch the screen but instead of rubbing and disturbing the puck surface the puck just spins the screen?

i like to ask questions and keep an open mind so new ideas can get in.
cheers.
jon

sweaner wrote:I would have to agree with John here. The water is still coming essentially straight down regardless of the shape of the screen.

I would say yes except that there is a finite amount of space between the screen and the puck. We have to ask:
1. How much space is there?
2. Does the water REALLY have time to evenly distribute across the puck in that space in that period of time, given the flow rate?
3. How much water will penetrate the puck as water fills this space, before pressurization begins?
4. When the puck begins to expand, how will this affect the space?
5. Etcetera.

Actually, we don't need to ask any of these questions, since the original comment was simply on matching the curve of the screen to the curve of the top of the puck.

Well, this would be logical if the espresso machine was on the Space Shuttle in zero-gee. However, here on Earth, the water is drawn down by the force of gravity. Even if you have a curved watering can and fill a curved bowl with water, the water will still form a flat surface.

The curvature of the puck and screen will have an impact on the headroom to be sure, but the many other variables may well minimize the other effects. The difficulty in testing this out is that even in comparing a curved and flat tamper, the tamp is affected, the headroom is affected, the extraction rate is affected, etc. so that it may be impossible to tease out curvature as an independent variable.

Adrian

drdna wrote:Well, this would be logical if the espresso machine was on the Space Shuttle in zero-gee. However, here on Earth, the water is drawn down by the force of gravity. Even if you have a curved watering can and fill a curved bowl with water, the water will still form a flat surface.

I dunno, it's possible that the nine(ish) atmospheres accumulating in that headspace might make it teenie bit different from that curved watering can spout and bowl.
I originally mused about this when I played with a buncha different tampers on the 'Tamper Roadshow'. Curved tamps were a bit new (at least to me) back then, and (IIRC) I didn't see a big difference between the two. The person that did had a curved dispersion screen, so I postulated that the two similar profiles might make some difference.
As far as I know, there hasn't been any real comparison since then, and none of that was more than a coupla guys playing with a coupla tampers, each on their machines.
I'd like to hear from the guys the developed these different profiles. How they came to the conclusion that these would be better, and what kind of experimentation they did.
Who invented the curved tamp, and why did they do it?

drdna wrote:I would say yes except that there is a finite amount of space between the screen and the puck. We have to ask:
1. How much space is there?
2. Does the water REALLY have time to evenly distribute across the puck in that space in that period of time, given the flow rate?
3. How much water will penetrate the puck as water fills this space, before pressurization begins?
4. When the puck begins to expand, how will this affect the space?

1. Depends on basket/dose/dispersion block. Presumably we're discussing "normal" dosing practices, not massive updosing a la Paul Bassett.

2. Yes, I believe so. Here's a simple experiment, perhaps not all that realistic, but the only easy one I could think of.

Prep a basket in the portafilter. Lock it loosely in the grouphead. Turn on the pump until water (and grinds) overflow the portafilter. It doesn't take long (only a couple of seconds) for water to completely fill the headspace. In other words, in the absence of brew pressure, the headspace fills before the puck saturates.


3. The time it takes for the first drops of espresso to appear after flipping the brew switch is sometimes called the dwell time. It's significantly longer than the time to fill the headspace (i.e., overflow the basket, as in the above pix). Brew pressure undoubtedly affects this relationship, but I don't know to what extent. It might be possible to make a WAG based on flow rates and puck saturation volumes.

4. Some folks claim that the puck compresses under pressure, and only expands when the pump is turned off. Sounds reasonable, but we may not know for sure until the mythical plexiglass portafilter video resurfaces.

Water is not very compressible. If the headspace fills with water (which seems likely), then the brew pressure should be transmitted evenly across the surface of the puck, regardless of shower screen geometry. That's why I have a hard time believing that the curvature of the shower screen has any impact on the optimal tamper shape.

I use both pretty interchangeably. I tend to gravitate to the 'piston should match the shower screen' theory. I have only had one machine that it appeared to make a difference on. At the same time, I have used a couple that had very radical piston shapes and those appeared to make a bit of a difference as well. But for your average Reg Barber style piston, I think there are many more important issues. The handle size makes more of a difference to me. The overall height, diameter of the handle and size of the palm swell on top all play into how comfortable the tool is. If it is out of proportion to your hand, you will have a tendency to favour one side and tamp off center which will be much more detrimental to your shots than the shape of the piston base IMHO.