Hi everybody, first of all, thank you for sharing so much information. I've been reading through H-B a lot in the last few months and your opinions and knowledge are a great resource. I recently upgraded from a SilviaPID/Rocky combo to a Brewtus/Mazzer Mini. I've scoured these forums for everything I can find about dialing in a new machine and my results are getting better, but I've noticed one consistent problem: channeling always seems to happen around the perimeter of the puck. So it got me thinking, would a larger diameter tamper be a good solution? I'm using an 18g Synesso style basket with bottomless portafilter and a 58 mm Espro tamper. The basket is 59 mm diameter, so would a Reg Barber tamper sized exactly to fit the basket be a worthwhile investment? Does anyone have any experience with a larger, tight-fitting tamper?

My opinion on this would be, no.

I used to have a 58mm machine, and now I have a 53mm, and for both machines I have simply bought either "58mm" or "53mm" tampers. None of them custom turned to size, just bought from various places(EPNW, Cafelat, Chris Coffee, Visions) and selected the size I needed. Ive also used a number of baskets, and there is always a slight amount of space, between the tamper and the basket.

I would suggest being more dilligent in your distribution, and keep the tamping very simple. One tamp, straight down, no tapping of the basket, no twisting to polish, just straight down, even force. Also, utilize the WDT for distribution if you're having trouble getting even pours.

My personal opinion on custom sized tampers is that, while maybe nice to have, a couple 1/4mm's isn't going to magically fix your shots. Spend the money on a custom made tamper if you appreciate and enjoy having a finely crafted piece of art, not because you're having channeling issues.

My tamping technique has devolved to just that. Get the grounds reasonably level in the portafilter and one good, straight down, tamp.

No NSEW, no nutation, no polishing. That all seems just artifice. I find with the above, I get consistent shots time and time again.

I have tried a couple things to eliminate the dreaded doughnut extraction. You could try a concave base tamper to get more side adhesion, a light nutating motion to help seal the sides and/or down dose. When I was having issues with the same problem I cut my dose down and the issue went away. I would not mess with getting a custom sized tamper. The tamp is one of the least critical parts of the process. A good tamp will not fix a bad distribution of dose, but a bad tamp will destroy a good distribution.

Thanks for everyone's input so far. I think my dose and distribution is reasonably correct: WDT, lightly shake and level the grounds before tamping, simple 30-40 lb tamp and no tapping on the side of the portafilter, just enough head space so the screen doesn't touch the puck, all the basics that worked well with the Silvia machine for 2 years and I still get frequent channeling with Brewtus. Brew pressure is right where it should be at 9 bar. I'll just have to keep experimenting, but I am still wondering if the gap between the tamper and the basket wall is at least partly to blame. If anyone has used a tight-tolerance tamper I would be especially curious to hear your opinion.

cannonfodder wrote:I have tried a couple things to eliminate the dreaded doughnut extraction. You could try a concave base tamper to get more side adhesion...

Concave or convex? To me concave seems counter intuitive?

AJQ wrote:Thanks for everyone's input so far. I think my dose and distribution is reasonably correct: WDT, lightly shake and level the grounds before tamping, simple 30-40 lb tamp and no tapping on the side of the portafilter, just enough head space so the screen doesn't touch the puck, all the basics that worked well with the Silvia machine for 2 years and I still get frequent channeling with Brewtus. Brew pressure is right where it should be at 9 bar. I'll just have to keep experimenting, but I am still wondering if the gap between the tamper and the basket wall is at least partly to blame. If anyone has used a tight-tolerance tamper I would be especially curious to hear your opinion.

2d on doughnut extraction

from Some thoughts on tamping (tamping twaddle, part deux)

5 tampers from just on 57 to 58.55mm. ZERO difference.

Either shake or WDT, not both.

It's impossible to 'seal' the basket edge. A water molecule is about 1/500th the size of the 'fines' peak.
Think beachballs [75cm], baseballs [7.5cm] and BBs [.015cm].

Yeti wrote:Concave or convex? To me concave seems counter intuitive?

Yes, fingers engaged before the brain.

The consensus seems to be that a tight-tolerance tamper doesn't make much difference. That's good to know. Thanks cafeIKE for the link to another discussion about tamping, your theory does make sense and I'll experiment some more with smaller dosing and more head space.