Puck diagnosis of obvious channeling

[framey]

I've recently switched from a Baby Gaggia to a Diadema Jnr. I always check my spent pucks, and with the Gaggia channeling was rarely apparent. I'm still getting used to the Diadema's idiosyncrasies, but the one thing troubling me is the fairly obvious channeling I'm seeing in the spent pucks. What seems even more vexing is that the channeling seems to almost exclusively manifest itself at 6 o'clock in the basket, ie nearest the handle.
Is this a sign of a particular dosing fault?
Is channeling more likely with ristretto pours?

All feedback gratefully taken onboard.


Stephen

[malachi]

Are you getting channeling against the basket wall? Or in the puck itself?

[framey]

Basket wall.

Nearly always occuring between 7 and 5 o'clock with the handle being 6.

I suppose the obvious answer is poor distribution after dosing. Maybe I'm neglecting the area nearest the handle.

I guess I was hoping for a " That occurs when" sort of answer. Rather than the " you suck at distribution" answer which unfortunately might be the most likely one.


Stephen

[HB]

I've seen what you describe. As an experiment, I have a few suggestions you might try:

• try dosing with the handle rotated 90 degrees from your usual (i.e., not towards you but to the left or right). Does the channel location change?
• try three rotations during the dose (dose, rotate, dose, rotate...)
• dose all the way to the top very lightly, cut off the top completely with your finger or straight-edge, tap the portafilter on the fork a couple times, then dose and level again.

Another longshot is that you're not wiping the basket well enough. The edges and holes trap moisture and sometimes baristas favor one side over the other. The encircled area below is such an example:



A quick test for this suggested by Matt Riddle is to knock out the (dry) puck. Nothing should be sticking to the bottom.

[framey]

Thanks Dan, I'll give each suggestion a go and see what happens.

I usually sweep N to S then E to W. I've been using a popsicle stick hoping to minimise uneven compression during distribution. Not sure if this practice has been proven to be unwise...?


Stephen

[malachi]

If it's against the basket wall there are two likely culprits. The likely ones are poor distribution or something which disturbs the distribution.

Poor distribution - I would ditch the popsicle stick. Seriously. As I say a lot - a popsicle stick doesn't have nerves connected to your brain. Use your finger. I would also strongly suggest doing two things when it comes to your dosing and distribution.
- start rotating your portafilter while dosing to even out the initial distribution,
- when distributing (with your finger) don't use your handle as the start or termination point. To illustrate - think of the basket as a clock. Instead of orienting the handle at 6 o-clock and going NSEW from there - orient the handle at 4:30 and go NSEW.
In addition, make sure that you're applying downwards pressure while distributing and that you're going all the way to the edges of the basket. This, to be honest, is hard to do without losing your "pile" that you're dragging and is one of the reasons I prefer the Stockfleths method of distribution.

Disturbing the distribution - if you (for example) whack the front (opposite side from the handle) of the portafilter with your tamper to knock off any loose grounds... and if you do so too hard or too many times, you will open a gap right at the handle. The seal will be broken. The goal of everything post-distribution (tamping etc) is to preserve the even density bed you've created.

Finally... I'd consider investing in a naked portafilter as a diagnostic.

[framey]

Thanks Chris,

I'll dump the popsicle stick, and get my spare single portafilter chopped.

I've been watching the Stockfleth move video and will work on it.


Stephen

[HB]

I've been trying my hand at taking videos of extractions for the Elektra A3 review. Problem is that they're huge to upload and serve. The good news is that most video editing software allows you to excerpt a single frame. That's an easy way of capturing the point you want to describe without having to fiddle with the camera during the shot.

I intentionally let the triple-basket extraction run long for the video, but otherwise it was a pretty good espresso.

[Ken Nye]

All of the above mentioned suggestions sound good. I am not that familiar with the machine that you are now using, does it use a rotary pump? If so, it will require a more precise distribution and tamp than your previous machine. Other possibilites are:

Check the filter basket for uniformity, check the hole pattern for deformities. Also, are the holes centered in the basket? Is the bottom of the FB flat, is the FB out of round? I mention this because I have encountered all of these problems with FBs at my shop. Any one of these will cause an uneven extraction.

Also, make sure that you have a good fit between tamper and basket. If you have too much gap combined with a tendency to finish your tamp towards one side of the basket, (most of us do) then you will end up with channeling problems at the perimeter of the puck.

Practice various distribution techniques. I like to over fill the basket, then tap several times on the forks, then fill again. When leveling with your finger, use a cross pattern and try applying a little pressure. Then tap lightly again (rubber mat?) before begining the tamp process. This may sound a bit tedious, but I cannot emphasize how important an even and full distribution is to extraction quality.

I hope that this helps.

[Ken Nye]

I forgot one thing... Get a bottomless PF. The Italians have been using them in their labs for many years... it is a great learning tool, and it pulls a beautiful shot.

[srobinson]

Checked out your movie. Taking coffee porn to the next level. Nice.

[framey]

Thanks Ken,

All tips and info greatly appreciated.

The Diadema Jnr uses a vibratory pump.

To my untrained eye the filter basket seems perfectly sound.

You might be onto something re inadvertantly finishing tamps on one side. I'll keep it in mind.

I'm trying to get the stockfleth distribution method happening. From all reports if done correctly it should work well.

I always dose till almost full then tap fairly firmly on a tamping mat I made. It is a stainless plate on a rubber mat. I then dose till the coffee is heaped and try the stockfleth move.

The bottomless PF is in the mail.

[afx]

I do have a similar problem...

While everything is fine when using my doserless Innova, I do have a slanted extraction from my Cimbali Jr. Always on the south half (close to the handle). The south half gets extracted and blondes quickly, the north half squeezes a few black drops through.
The south side is the side where the water comes from the brewhead into the dosing chamber. To eliminate the doser I also used a little bowl to collect the coffee bevore I put it ino the basket.
So far I had no luck in getting anywhere close to the even extraction that I get from the Innova. The burrs are just a year old and the grinder is only used as my secondary...

cheers
afx

[malachi]

How are you handling distribution?

[afx]

How are you handling distribution?

Either by finger or by a knock or two on the counter (vertically). Not much of a difference.

cheers
afx

[malachi]

I would suggest you experiment with a more rigorous distribution method. It should solve the described problem. Either the Schomer method or the Stockfleths one should work.

Dose (using the doser) from the Cimbali until you have a good heaping pile.
(Optional depending on desired dose: Give it one to three quick raps vertically against the grinder fork.)
Top off the dose to create a heaping pile.
Distribute using one of the methods above.
Tamp.
Go...

[HB]

Always on the south half (close to the handle). The south half gets extracted and blondes quickly, the north half squeezes a few black drops through.

I've noticed the same thing with Junior and attributed it to (a) uneven distribution due to factors like dosing w/o rotating the portafilter, or (b) filling high enough to grate the puck on the south side during lock in, but not high enough to get the "Paul Bassett" updosing effect (which renders the grating irrelevant since the whole puck surface is intentionally grated pretty hard). Chris also mentioned in another post baristas that favor one side when tamping will see south-side channeling.

A remote chance is that the brew pressure is too high. I intentionally raised it to produce some of the more disasterous effects for Perfecting the Naked Extraction, like this one I called "System Meltdown":



The pressure was set to 11 bar.

[PheasantCreek]

I'll toss some weirdness that can occur. On my used Super Jolly it is missing a deflector screen in the doser. What happens is the finer grains fall close to the edge and the courser grains fall near the middle. When dosing, tamping and pulling the shot it will act like a canted tamp. Nothing will get extracted in the 6 o'clock half of the portafilter and the other half gets overextracted.

Of course nothing a well placed and bent business card couldn't fix!

[framey]

I think I've solved my channeling problems, for now anyway. After trying many of the suggested fixes the thing that helped was changing my tap in between tamps. I tamp, tap, tamp then lightly polish. The tap was light and directly opposite where I was getting the channeling. I tried tapping even more lightly and with a more glancing blow, but this time I tapped one of the lugs. So far so good.
Is there a known problem with tapping the lugs? Do they become misshapen over time?
The best thing is, in trying to fix the channeling I've gotten some great tips and more than likely improved my distribution and levelling.