ifeghali wrote:with a double shot basket, 18g, lowest grinder setting, pressure gauge doesn't even reach espresso range (9 or 10 o'clock).

with a single shot basket, 9g, lowest grinder setting, pressure gauge goes up to 12 o'clock or maybe a little more.

will keep working on my prep skills. thanks.

If you're only getting to 9-10 o'clock with the double basket, then you are definitely under-extracting and will need a finer grind.

tinroofrusted wrote:I have a Breville Bambino with a naked portafilter and was having that exact same problem for quite a while. I had those squirting streams emanating from the portafilter. Not pretty! I can tell you how I fixed it for me and I'm pretty sure it could work for you too. For each shot you pull, add a 1.75" circular coffee filter paper at the bottom of the portafilter basket

dude, the paper filter fixed 95% of the problem for me. it's acceptable now but I feel like cheating LOL

I was going to suggest that worst-case scenario, you could revert to using the dual-walled portafilter, but glad to hear that the paper is helping. There's this very detailed article by Jonathan Gagne on how paper affects hydraulic resistance in a puck: https://coffeeadastra.com/2021/04/04/ho ... esistance/

Interestingly, people report usually having to grind finer to achieve the same flow rate when they weren't using a paper filter

luckydragon wrote:Interestingly, people report usually having to grind finer to achieve the same flow rate when they weren't using a paper filter

tried grinding finer with my manual timemore C2 up to the point where no coffee would flow anymore. no luck.

i guess i'm stuck with filter papers LOL. 3d printer already fired up to make the cutter.

appreciate your help.

FYI, paper filters are not fixing the problem.

They are masking it.

The issue with channeling and spritzers is one of distribution in the basket and water finding preferential paths through the puck. When that channel of water hits the perforated surface of the basket, it jets through and makes a mess. You never see the issue with a spouted PF, because the bottom of the PF collects all errant streams and directs them into the spouts.

The purpose of the bottomless portafilter is to identify issues in puck preparation and address them. I'm glad the paper filters have reduced the mess made by an improperly prepared puck, but please do not think that this addresses the root cause any more than going back to a spouted portafilter would. What is happening is the jet of water is now hitting the paper filter and being diffused across a much larger area before it hits the perforated surface of the basket. The diffusion can be beneficial when a puck is prepared properly, but still exhibits preferential extraction in the absence of channeling. However, if you have spritzing and spurting without the paper, you still have the same root causes at work in your puck with the paper. If all you want are pretty bottomless pours, and are not concerned with the flavors that you are getting, carry on.

But remember that the bottomless portafilter exists as a diagnostic tool for a reason. Well-extracted shots generally taste better than shots extracted with lots of channels. The purpose of the tool is to refine your skills until the tool demonstrates that the issue is resolved. At that point, you can put the tool back in the drawer and use a spouted PF if you wish. Pull out the bottomless portafilter if you taste something off with your shots and want to understand if your prep needs work. Hiding the problem with a paper filter makes the tool useless. It's a bit like putting a smiley-face sticker over top a check-engine warning light on your dash - "All better now".

Cheers!

- Jake

Great description by Jake. A paper is a good option for clean up, for using a coarser grind, and, proposed by some, helping with edge extraction. It in no way helps with channeling. It is something to be experimented with after basic puck prep is solved, not as a bandaid visual fix for jets.

Channeling is caused by pressurized water FOLLOWING PATHS OF LEAST RESISTANCE.

The goal of skilled puck prep is to eliminate permeable paths and present the group with uniform hydraulic conductivity and uniform thickess for a more uniform CONDUCTANCE (Area*Kz/b') along elution flow path.

Every grinder yields a characteristic PSD (Particle Size Distribution), for a given bean, roast & fine/coarse setting. It is affected by bean brittleness, more brittle for dark roasts, less brittle for light roasts. If you are experiencing channeling, start by mixing the powder with a tool. This randomizes the mechanically sorted (fractionated) grain size laminae that form as coffee falls into filter basket.

There are two fractionating processes, mechanical roll sorting in which the coarse grains tumble further down slope (end-dump fractionation), and air-hydraulic resistance that slows the finest grained particles so they stop sooner. They happen simultaneously and you could do a dissertation on this process (probably has been done).

Small-scale grain-size sorting develops along the angle-of-repose slopes in the basket during coffee powder deposition, creating invisible stratigraphy or laminae that act as preferential flow paths. The coarse grains present paths of lower flow resistance. Disrupt these paths for better extractions & flavor.

If mixing and tamping does not resolve problem (channeling) then fine your grind. Use bottomless to check your work. Puck prep is the 4th "M", manno.

--Deuxinfuso, Reno, Nevada
(Current rave fave: Copantrade La Fortuna)

Jake_G wrote:FYI, paper filters are not fixing the problem.

They are masking it.

Hi Jake, thanks for the explanation. I tried everything I could, I can't get it done right no matter what. Have called a barista friend to come help me let's see how it goes.

You're very welcome!
Record a video of your WDT routine. That will pretty much give us everything we need to know to fix your problem.

Also, you can almost certainly shim your grinder to grind finer. Old smart grinders (which is what you have in your combo) came with 2 or 3 shims in the box specifically to adjust how fine they ground because what works with the double wall basket almost never works with the single wall basket...