High sensitivity of extraction to grinder settings?

wilburpan

This may be weirdness I’m seeing just from my particular set up, but thought I would ask. I have a 9Barista, which means that the extraction just goes when the internal temperature/pressure hits 9 bars. Once it starts, I don’t have any real control over the extraction. My control over the espresso is primarily from the setting on my DF83 (stepless grinder) and the dose. I’m used to using 19g all the time, and adjusting the grinder setting to tweak things.

My experience is that a range of grinder settings over 5 tick marks or so gives me extraction times of 20 to 60 seconds, and if I go finer, then the 9Barista may choke, at which point the safety valve goes off.

With my current bag of beans, a grinder setting of 17 results in a 25s extraction, with 38g of espresso coming out. This setting is a little on the acidic side, with a little less body than I’d like. Still good, though.

My usual move here is to go a bit finer on the grind, and what I would expect is that as I go to 16, 15, and so on, the extraction time would go up by 3-4s for each tick mark, and the taste would shift as you might expect.

What has happened is that if I go the slightest bit finer than 17, the extraction time goes up by A LOT. In fact, it appears to me as if the coffee is fine enough that water isn’t making its way through the puck, and diverts out the chimney instead. The espresso that does come out is shifted in the taste direction I would expect, but the amount of espresso is considerably less, about 25g. I think that this is a result of some of the water going out the chimney instead of through the puck.

I know part of this is probably unique to the way that the 9Barista works, but it seems that with a conventional espresso machine, a small change with a stepless grinder usually results in a small change in the espresso. I think the analogous situation with a conventional espresso machine is having a small change on a stepless grinder setting resulting in a considerable difference in extraction time, if all other settings were kept the same.

Has anyone seen this?

MWJB

I there any way to get more liquid out before grinding finer than 17?

How do you end the shots?

wilburpan

MWJB I’m using a 9Barista. It’s a stovetop espresso maker. One aspect of this machine is that once the extraction starts, it just goes until it stops. There’s no direct control over when the shot ends other than adjusting the grind and dose. So if I wanted the extraction to go longer, I could either grind finer or increase the dose.

What is new for me is that there seems to be no middle ground between a 25s shot and nearly choking the machine.

Again, my question is whether anyone has seen this sort of behavior with a conventional espresso machine.

mobius

wilburpan I have seen similar on some beans with my E61 Classika. I haven’t found any particular correlation, but it will also vary depending on the basket being used.

With my current bean, using a Comandante C40 red clix (15 microns each click), the rough times for the same in/yield at each ‘click’ go as follows: 23s->30s->48s->choke

If I need more variance aside from shot length, this is where I will usually increase/decrease the dose (starting by 0.5g) as that can make a difference as well.

EDIT: At least I thought that’s what I did… but just following this, this morning, I increased my dose by 1g (for other reasons) and the time only changed by ~1s… So it seems I’m misremembering previous attempts, or this is something else. I need to go back and check all of my records now !

tompoland

Following with interest.

wilburpan

Turns out that there probably was an issue with one of the o-rings in the 9Barista. I disassembled the 9Barista, made sure that the o-rings around the bottom boiler part and the valve pin were seated properly, and put it back together. It’s behaving as expected now.

My guess is that by grinding finer, I managed to hit the point where a poorly seated o-ring allowed the pressurized hot water to find an alternative exit through the chimney. Reseating the o-rings resolved the issue, although there wasn’t any visible issues that I could find.