Unimodal donut extractions

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maccompatible
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#1: Post by maccompatible »

I am perplexed. I swapped out my baratza vario's ceramic burrs for the ditting 54mm steel burrs they sell, which seem to be much more unimodal. I've had some odd consequences of this, but by far the most confusing is the channeling I've been getting. Seems like no matter what I do, I end up with only the edges of the puck extracting, and sometimes the very center at the bottom will knock out and look completely dry! I am using the exact same basket, machine, tamper, etc. as before. I spend 20-30 seconds with the Sworksdesign WDT tool and make the bed as even and clump free as possible. The grinds look nice, fine, and even on visual inspection with the new burrs. And even trying to push more coffee to the outside, an intentionally less even bed, will still not get water to push through the center of the puck. Any ideas? The only thing I can come up with is POSSIBLY the paper filters I bought for the bottom of the basket are somehow encouraging channeling around the very edge? They don't go from edge to edge, but do cover all the holes, even if they were to slide a bit during puck prep. But I was using these even before swapping burrs no problem.

Setup:
LM GS3 with stock 17g precision basket
Baratza vario with steel burrs and flapper mod, otherwise stock
Beans are a variety of light to medium home and local roasts, all 1-2 weeks post-roast
WDT tool, RDT spray, and paper filter at the bottom of the basket
200*F, flat 9 bar extractions
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Jeff
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#2: Post by Jeff »

You can easily test your theory about the papers.

Other ideas are that you're grinding too fine or that the basket is damp.

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baldheadracing
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#3: Post by baldheadracing »

After you've tried the first steps that Jeff has given and there is no improvement, then here are some other things to check:
- did you change the burr mounting screws? The mounting screws for the steel burrs are different from the screws for the ceramic burrs;
- the burr mounting surfaces have to be fastidiously clean. Wiping with a paper towel with rubbing alcohol on it is a good check; and
- does your Vario have the Forté's steel grind chamber retrofitted? In my experience with an older Vario with the plastic chamber, you'll want that for espresso - and possibly/probably hyper-aligning.

Good luck!
-"Good quality brings happiness as you use it" - Nobuho Miya, Kamasada

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RapidCoffee
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#4: Post by RapidCoffee »

Maybe grinding too fine with the new burrs?
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PIXIllate
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#5: Post by PIXIllate »

I swapped my Vario ceramics for the steel when I moved it to filter duty. They needed about 20lb of seasoning to start to behave and taste right.

maccompatible (original poster)
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#6: Post by maccompatible (original poster) »

I made a few changes at a time this morning. I used a darker roast, higher dose, and no paper. I made a pretty small grind adjustment (3 micro clicks) and the donut channeling was gone, but it also pulled too fast as well (17g in, 42g out in 24 seconds). Gonna keep working on it, but it's starting to feel like the lack of fines is making dialing in nearly impossible..
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Jeff
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#7: Post by Jeff »

There is nothing that says 1:2 in 25 seconds is "right" for all gear and coffees

maccompatible (original poster)
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#8: Post by maccompatible (original poster) replying to Jeff »

I understand that. But with darker roasts, especially this one, my preference is usually 1:2 in ~30 seconds. 1:2.5 in 24s tastes weak, sour, and roasty.
I decided for now to move my vario to work for the time being. I use a flair here and it's much more forgiving with grind setting and also takes a coarser grind. First shot on this setup was beautiful this afternoon. Of course, this means moving my encore back home to pair up with the GS3, admittedly a bit goofy, but it's doing a more consistent (and tasty) job with espresso right now. Maybe my grinders will shuffle again once my Lagom P64 gets here, but for now I'm giving up on the new burrs with the GS3.
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cmin
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#9: Post by cmin »

Since you just mentioned dark roast, the steer burrs are not going to be great for that. Their very unimodal, I have both sets and aligned for years. The Ceramic burrs will be much better than the steel burrs for say darker medium to dark roast, they can still do lighter but that's where the steel set will excell for. Though I really only used mine for brew. Can't really compare to Flair but yeah like you said the Flair works with a generally coarser grind than machine.

I'm primarily using my HG1 Prime (and had an HG1 back in the day). Do love that burr set, it's just excellent whether dark or light roast.

Far as donuting don't use the papers and see what happens. I would check alignment as even with the old plastic base it can be finicky and end up out of wack after. Really need the Fortes steel unit which you cna buy from Baratza and install. Should be fine on darker roast, but when you go lighter the plastic will struggle and flex it can't handle grinding that fine on hard light roast and steel burrs as you go way finer than the ceramic. Just swapping in the steel burrs on a reg Vario will struggle for espresso like many find/found out. I've had both grinders with both sets side by side (still do but packed up, pull out once in awhile lol). Just as an example, I have a DF64 as another grinder just to see when they launched. I still prefer the Cermaic Burr for espresso vs ital or cast lab sweet style, and steel burr isn't close, steel burr Vario aligned will wallop that grinder for brew and don't have to deal with the DFs wonky ass use and issue with fines/dust etc. DF is still noticeably muddy on V60 vs Vario. I really didn't like the Ital burr set at all.

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Brewzologist
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#10: Post by Brewzologist »

Someone with way more expertise than me suggested that unimodal burrs may produce more smaller coffee particles, resulting in a bed that can be harder to penetrate. So, maybe try a coarser grind and see what happens? I run MP burrs which are quite unimodal and I have to grind coarser for best results.