Uneven extraction

[shadowfax]

(split from The Denver Effect by moderator...)

I wonder something.... the dark spots I am getting, I noticed, always seem to be on the side where i get the slower extraction. I can't seem to get a perfectly even extraction.

these are reasonably typical of my extractions right now:
Monday morning's shot:

Which turned into this:

This evening's:

Which turned into this:


Monday's kinda sucked. It was brewed a little hotter (5 oz flush; this evening was closer to 7oz.), but I feel like the worst of it was how unevenly it started out. Granted, they both started out unevenly, but Monday's was much worse... at any rate, they both have the dark spots on the side where you see the darker extraction.

What do you think, Chris? I suppose I should really be perfecting my distribution before I go looking for other culprits for mediocre shots, huh?

[malachi]

you've got uneven density in the basket.

[shadowfax]

well, that seems obvious enough to be a tautology. I know I do, and I am having the darnedest time getting my distribution right. I've read the different methods, and used to have a lot of luck with Stockfleth's on Silvia, but it doesn't seem to work right for me anymore. Maybe I am just way out of practice. It took me almost a month to get good on Silvia, and I have had a month break from doing anything coffee related, so this is basically the start of week 2 of being a newbie all over again. the concepts are fairly solid for me, it's just... not having experience with them, I guess. I have known my distribution is off since I got the machine, and I have been, again, focusing my efforts on and racking my brain about that in addition to wondering about all this flushing and boiling points and all... I guess I'll just keep plugging away.

[buzzword]

Newbie for the first time

You can't see below the level surface; density is hidden; method or feel for density are the only things that can create even distribution.

The natural thing would be to say, for whatever reason, you've got more packed (so per malachi distributed) at around 1:30 o'clock, so add coffee at around 7:00 until the problem moves somewhere else.

malachi is like an oracle; his attention to the immediate is like a beacon shining brightly from the direction of excellence, but between me and the light is terra incognita (a Nabokov story title).

[Teme]

I have tried different methods for the distribution and tamping. I have noted that these have helped me eliminate the problem you describe:

- When dosing and the basket is 3/4 full, I tap it on the tamping mat vertically a couple of times to aid distribution. I then finish the dosing, level (no pressure, but making sure its even) and tamp.

- When tamping, I try and avoid tapping the PF to drop the ground coffee from the sides of the PF to avoid channeling. I'd rather have some ground coffee left on the sides of the basket. If there's too much of it I'll tap, but just once.

- Even, consistent and strong enough pressure when tamping (I tamp at approx. 15kg / 33 lb). I've noted a big difference here and my first tamp is as hard as the final tamp. I ease the pressure for the polish. If my tamp is lighter, I usually get similar results to yours (at least to some extent) and/or random sprays of coffee.

- Related to the previous one - initially I sometimes unintentionally tilted the tamper when tamping. The puck was higher on one side than the other. I practiced to eliminate this. By extending the index finger and thumb after the tamp, and then turning the tamper to polish, with the extended fingers you feel if the there is a "wobble" that would indicate a "tilted" tamp. I now have the hang of it, but occasionally I do check, just to make sure...

There might also be differences between baskets. For some reason, I find the LM ridgeless double good in terms of my results.

I am also a relative newbie, definitely one in this company, and therefore also interested in further comments...

Br,
Teme

[shadowfax]

Teme, thanks, those are very good suggestions. I already do a few of them, like checking that the tamp was level. I've always avoided tapping, even straight vertical tapping. Maybe I'll give that a shot.

[malachi]

Oracle?!?!

Now that is a scary idea.

Given that you see light density near the handle, I'd look at your dosing (make sure you're not front-loading the dose) and your distribution (you might be "working around" the handle when distributing).

[buzzword]

! speaks

This is a great site.

[Dripp]

I too have had issues for 6-8 weeks with uneven extraction. Most of the shots were ok, and rarely were they great. My best shots were decaf in the evenings. My issues were always on the right side with overextraction, with the left side being good or underextracted. In another thread, it recommended I read, or re-read as the case may be, "perfecting the naked extraction." And there, in the hall of shame, was a picture of my shots of late staring me in the face. It seems that in my efforts to cure my underextraction, I have been over filling the basket or tamping too lightly, and when inserting the portafilter, I have been slicing the top of the puck. Now I can't wait to get up and try this out.

Admittedly, I don't have a scale for the grounds or the tamp which could help me solve my woes.

[tweeek]

Given that you see light density near the handle, I'd look at your dosing (make sure you're not front-loading the dose) and your distribution (you might be "working around" the handle when distributing).

I've changed machines and got a naked PF in the last two weeks and until yesterday was seeing consistently uneven extractions. I was regularly seeing a light patch at the front (12 oclock, with 6 at the handle) of the basket. Then after reading this thread, I started to think about where the grinds were going when coming out the grinder spout.

Since that epiphany, the pours are starting to even out.

Seamus

[Paul L]

I have yet to look for naked portafilters here in the UK, however I'm interested in reading the various distribution methods mentioned through the thread. Where can one read up on them?

[HB]

The Resources page lists several articles and videos under Extraction Diagnosis. If you find other noteworthy articles that I've omitted, please let me know.

[Paul L]

Silly me, of course Dan. As my bookmark goes straight to the forums I tend to overlook this. Looks like I have plenty of reading to do and I need to re-bookmark. Thanks.

[cannonfodder]

I rotate my PF on the fork of my Mini while dosing. I hold the handle 90 degrees to the left, first dose falls in, rotate the PF 180 degrees so the handle is now to the right, next dose, then back to center to finish, sweep level, tamp and go. It made a difference for me. When the grounds drop into the basket in one spot I think they tend to compact from the drop and impact from each subsequent dose. By rotating the PF with each dose I seem to get better distribution. I also give it one or two light downward taps onto my tamping table prior to the leveling and tamp.

[default]

dosing makes them all difference. let me share my observation.
1. the speed of flipping the flap. on mazzer mini, the faster you load, the more ground will be on the left. either compensate it by vary the speed of flipping the flap or turn the pf around. the way the ground falls different from machine to machine.
2. here we don't really have static, so i don't know how to handle that. but when i do something dark, i'll wait for the ground to fill 2/3 the small bucket in the dosing chamber before swapping. it really helps.
3. i aim for a small hill and tap it down, the more i tap, the more ground i put in. try to be consistent.
4. level it off and tamp.

[Abe Carmeli]

Dose directly into the basket, not the P/F. Keep the P/F in the machine at all time. As you dose, rotate the basket 360 degrees. About every 2 pulls of the mini doser, rotate the basket 1/4 of a turn. Tamp into the basket. When you are ready to pull your shot, just drop the basket into the P/F.(You must remove the spring from your P/F to use this technique). You may read more about that method here: Barista Technique Used in this Review

[cannonfodder]

Keeping the PF in the machine while you dose and tamp your basket will keep the PF at temp, but shadowfax is using a bottomless PF (as do I). Doesn't the lack of bottom mass in the PF limit the functionality of this method? Or do you do this strictly for dosing reasons?

[Abe Carmeli]

Keeping the PF in the machine while you dose and tamp your basket will keep the PF at temp, but shadowfax is using a bottomless PF (as do I). Doesn't the lack of bottom mass in the PF limit the functionality of this method? Or do you do this strictly for dosing reasons?

I use this method regardless of the P/F. With a bottomless, there is less of a heat sink to deal with, and the benefit is mostly in better distribution, and preventing premature cooking of the coffee grounds.

[malachi]

Actually, I have yet to see any real evidence that dosing into the basket outside of the portafilter has any positive results and, in fact, have seen some negative results in many instances (unsettling of the bed, grounds on the bottom of the basket, etc.).

In most cases, I would predict that subtle improvements in barista techniques will bring better results.

On a related note... it seems like a lot of the things people do in coffee that seem odd are attempts to work around barista weaknesses rather than work on them.

[Abe Carmeli]

(unsettling of the bed, grounds on the bottom of the basket, etc.)

.

What exactly are you referring to there?