Vario single-dosing, distribution, and donut extractions

Grinders are one of the keys to exceptional espresso. Discuss them here.
FinnLight
Posts: 97
Joined: 11 years ago

#1: Post by FinnLight »

I did a bit of searching and couldn't find a exact match so here goes.

I have had the vario for 8 months now and have been mostly single-dosing the whole time. From the beginning there has been a donut extraction visible from the naked PF. What I have done up till now to offset this, I have used WDT in the PF to break the mound toward the edges and actually make a divot to the center so that the extraction is visually even. While this has worked, I have always felt that I was doing this incorrectly since I don't see this kind of technique advertised here. I was suspecting that I was overextracting the middle big time since the amount of grinds there was considerably less.

This morning I had an idea about the behavior of the burrs on the vario while single-dosing. I reasoned that there is little play in the adjustment mechanism. When single-dosing, this causes the burrs to lie closer to eachother at the beginning of the grind since there is less coffee between the burrs. Same goes for the end of the grind when the burrs clear of excess coffee. This behavior would now cause a batch of finer grounds at the beginning and the end of the grind. Normally, I had been directly dosing into the PF and the first batch of grinds lands in the middle where it potentially blocks the flow.

I tried to modify my distribution a bit. I kept everything else the same except distribution. I began by grinding to the front edge of the basket and then moved the PF so that the basket filled as evenly as possible. After grinding I used the WDT just to re-distribute the grinds evenly but kept the amount of grinds in the middle same as elsewhere so no divot. The extraction showed a dead-spot where the first batch had landed in the basket and the middle was fine and even. I did not have time to verify this yet, so it is early to jump into conclusions but it seems there is some truth to this. People who use the container with the vario should not have this kind of woes, but those who directly grind into the basket could benefit from this.

Has anyone else noticed something similar?

Edit: If I am correct, this would also explain why you have to tighten the grind setting quite a bit when going from single-dosing to using the beans in the hopper. Doing this reduces the amount of fines in the grind considerably and therefore faster flow which has to be compensated.

Edit2: If this proves to be true it would also mean that single-dosing should be avoided with vario because the particle size distribution changes during the dose grinding whereas using beans in the hopper would result in much more bimodal particle size distribution. Feel free to correct me.

FinnLight (original poster)
Posts: 97
Joined: 11 years ago

#2: Post by FinnLight (original poster) »

Ok, test number #2. I ran few beans through the vario to clear stale grinds. The I ground into a cup, little shake and dumped that into the PF. Evened out the coffee with NSEW and pulled.

Result:
Visually even ristretto pull that did not blond too early. Blonding around 30s from pump start, first drops around 10s mark. Taste test.... well by far the best of this blend. Full and rich with no sign of acidity. Actually the result was a little too sweet with a hint of bitterness so I will adjust accordingly, but this is an exiting result in this barista household. I guess next I will have to move to using beans in the hopper so that the grind is as even as possible.

I think it would be exciting if other vario owners could confirm this behavior as it could also just be my vario that behaves like this.

jedovaty
Posts: 536
Joined: 13 years ago

#3: Post by jedovaty »

When I had the vario-w, I found I had more consistent results with beans loaded in the hopper, although I had had luck single dosing. I always did a quick stir of the coffee in the basket with a needle before pulling a shot, and this was pretty much exclusively with a mypressi twist.

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bostonbuzz
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#4: Post by bostonbuzz »

Grinding into a cup has the same effect as WDT'ing - taking that wisdom from the HG-one mega thread. I found the only way to avoid doughnut extractions with a vario (short of WDT or some messing with the grinds) is to pay extremely close attention to dosing.

You make sure that the first place the grinds go is around the corners of the basket as evenly as possible. Once this is done, you fill in the middle, and then go around the outside, then fill in the middle, etc. ending with a PERFECT cone of grinds on top. Tamp straight down = perfect extraction. It takes some practice. The most important point is getting the corner first.
LMWDP #353

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[creative nickname]
Posts: 1832
Joined: 11 years ago

#5: Post by [creative nickname] »

With my Vario, I get best results using the following approach:

1. Keep the hopper filled whenever possible. (I use hand-grinders for single dosing, for the most part.)
2. Grind our a few grams at the start of a session, to purge any stale grinds.
3. Grind directly into portafilter, paying attention to distribution. Weigh before and after to double check timed dosing.
4. Tap to settle grinds, NSEW swipe. Tamp.

I almost never get donut extractions with this routine, FWIW.
LMWDP #435

sqroot3
Posts: 87
Joined: 11 years ago

#6: Post by sqroot3 »

for my education and for discussion,

what baskets are you guys using? finn, i take from your profile you're using the strada straight-walled basket?

how much of a doughnut/bagel/fruit loop are we talking? is the center dead for, say, the entire extraction (would seem unlikely as eventually the drops coalesce), the first half of the extraction, or the first n seconds after preinfusion?

do you guys really get better results (less doughnutting) if you tamp down a mound of coffee versus a level basket of grounds? now that i am used to it shooting ever so slightly to the left, i can usually coax my b-vario into getting me a nice mound, but i almost always level the coffee before tamping. haven't tried tamping the mound in a while...maybe i will.

FinnLight (original poster)
Posts: 97
Joined: 11 years ago

#7: Post by FinnLight (original poster) »

Sqroot3, I am using straight-walled ridged strada baskets. I could try the NS stock basket but I had the same problem before I changed my baskets. The dead-spot stays dead depending on the shot volume, that is, with a ristretto the center stays dead entire extraction and with a normale it might might stay dead half of the time.

I tried to just tamp the mound directly few times but that results in even worse doughnut extraction. The in PF WDT I did only redistributed the grinds, but did not disturb the bottom of the basket since I tried to avoid that for some reason. :roll: So yes, you want to level your grinds before tamping.

FinnLight (original poster)
Posts: 97
Joined: 11 years ago

#8: Post by FinnLight (original poster) »

I am getting more proof to this. I put beans in the hopper, so no single-dosing this time. This should remove the finer grinds at the beginning and end of the grind when single-dosing. I kept the dose the same and distributed grinds evenly.

Result was 28g in 32s so it poured about 10g more during the same time. A considerable difference in my mind. The extraction was also even with no dead-spots. Taste was also more balanced and fruitful compared to the uber sweet ristretto of the single-dosed pull.

FinnLight (original poster)
Posts: 97
Joined: 11 years ago

#9: Post by FinnLight (original poster) »

Ok, vario is misbehaving again.

Yesterday, I had put some beans in the hopper after single-dosing. Setting was 1I and single-dosed produced 18g in 32s while the non single-dosed produced 28g in 32s. This morning I tried to pull another tasty espresso. I cleared stale grinds and pulled a 20s gusher. WTF??? I had not touched anything. Does leaving beans in the hopper over night result in that kind of difference in shot flow? The beans are 18 days old.

Adjusting vario was a pleasure again. I did 3 sink shots and ended up turning the setting to 1A, a whole 8 notches finer to produce about 28g in 30s. And then there is the overshoot problem. A shot made after the successful one produced a 18g ristretto in 40s. I hate my vario. The adjustment mechanism is so bad. I need something with threads...

Has anyone figured out any smart way of working the vario adjustments? Single-dosing the adjustments do seem to kick in a little faster, but then you have the finer grind problem described above.

IMAWriter
Posts: 3472
Joined: 19 years ago

#10: Post by IMAWriter »

18 day old coffee. Could be the problem.
Have you cleaned your Vario in a while?
I guess folks single dose in a timed (Vario) or weighted (Vario-W) so they can switch coffee?
If so, I'd recommend grinding into bin. WDT it, a quick stir, and use either a cut-down yogurt cup or an OE (Orphan espresso) funnel.
As my Vario-W is mainly for espresso, I just keep the hopper 1/2 full.

Back to the 18 day old coffee. That is a HUGE variable, especially of it is now oily.
Vario doesn't do so well with uber oily coffee.

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