Monolith Flat variable speed rescues ultra-light roast!

Grinders are one of the keys to exceptional espresso. Discuss them here.
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Peppersass
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Postby Peppersass » Aug 14, 2019, 1:18 pm

I've had my Monolith Flat since the first production run, and honestly I haven't found a use for variable RPM -- until now.

As reported in another thread, while on vacation in NYC I picked up a bag of Apes and Peacocks Zambian natural SO from Underline Coffee in Chelsea. I tried a shot of it at the cafe, and while it was rather under-extracted, I could taste some interesting potential, confirmed by blueberry notes when I sniffed a bean sample offered by the barista.

When I opened the bag at home, six days after roast, I immediately noticed that the roast was ultra light and there wasn't much aroma -- certainly not what I smelled from the cafe sample, which was probably from an earlier roast. What really blew me away, however, was that my Kafatek Monolith Flat couldn't grind it fine enough. This was a first for my beloved Flat, which I've owned since the first production run and recently upgraded with SSP burrs. I've never gotten close to the finest grind the Flat can do, so I was astonished when I got a gusher with the grind setting just barley coarser than the point where the burrs touched.

To be fair, I've been pulling singles exclusively for some time now, so the low dose was clearly part of the problem. I boosted the 8.5g dose to 17.2g in an 18g VST double basket. That helped a lot, but the shot still ran too fast, barely 25 seconds -- nowhere long enough to extract the ultra light beans properly. The shot was similar to what I tasted at Underline, so I figured the roast would push the limits of any grinder, and resigned myself to letting the beans rest at least a week longer before trying them again.

But overnight it struck me that there could be another solution -- bump the Flat's RPM! I've been running the grinder at 450 pretty-much since I got it, and have never played with different RPM settings. So this morning I set the Flat to 800 RPM (still the finest possible grind setting) and let it rip. Sure enough, the flow rate slowed way down. In fact, it was a bit too slow, over 50 seconds. The shot was still tart, yet much more drinkable, but no fruit flavors survived the long pull. I dialed the Flat's RPM back to 650 and that lowered the shot time to about 40 seconds, where the fruit flavors started to emerge.

Personally, I think the roast is just too light, but it's possible there'll be some improvement after letting the beans rest. I'll report back if there's any change.

For me, the takeway is that there really is value in having a grinder with variable RPM -- even if it took three years for me to find a use for the feature!

[Afterthought: While writing this it occurred to me that another solution would be to dig up one of my older standard double baskets, which should have smaller/fewer holes than the VST 18g basket.]

Quester

Postby Quester » Aug 14, 2019, 1:51 pm

I've been grinding a bit faster with lighter roasts on my EG-1 for the same reason.

I'm not totally sure it helps, but I'm leaning that way too.

yvizel

Postby yvizel » Aug 14, 2019, 9:51 pm

Thanks for sharing!

mathof

Postby mathof » Aug 16, 2019, 6:28 am

Peppersass wrote:Personally, I think the roast is just too light, but it's possible there'll be some improvement after letting the beans rest.

If you have a refractometer, perhaps you could do a straight-forward immersion brew of your coffee and measure the EY. If it's lower than comparable roasts, wouldn't that show the problem is with the roast?

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Almico
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Postby Almico » Aug 16, 2019, 8:36 am

I stay around 800RPM on my VA Mythos II. Slower doesn't help.

Interestingly, I'm in the camp that feels slower RPMs benefit conicals, but not the same for flats.

N6GQ

Postby N6GQ » Aug 16, 2019, 9:03 am

Very interesting and since I do most of my roasts on the VERY light side, its a variable I intend to play a bit with - thank you for pointing it out. I've kept my speed setting constant since I got my MonoFlat/SSP about a year ago. What I've noticed is that depending on what you are looking for in terms of primary flavors, there's definitely a window of aging that works best (duh). But what I didn't expect is that for some very light roasts, that window of preferable fruit flavors is often much longer than you would intuitively think. For example, Ethiopia Sidamo is my favorite variety for the blueberry essence, and I've had some roasts that the primary flavor is apparent from day 2, and others where the blueberry primary doesn't come out til week 3. Vastly different and while the bean source was the same, the lightness of the roast was ever so slightly different (and other variables are the same, to the best of my ability). Maybe that's a tipoff that my consistency isn't as good as I think it is? :oops: Haha. All fun.
LMWDP #614

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Peppersass
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Postby Peppersass » Aug 16, 2019, 1:46 pm

mathof wrote:If you have a refractometer, perhaps you could do a straight-forward immersion brew of your coffee and measure the EY. If it's lower than comparable roasts, wouldn't that show the problem is with the roast?

I do have a refractometer, but I don't need it to tell me that the roast is ultra light. The beans are practically blond and I have quite a few years of tasting various levels of espresso roast under my belt, as well as experimenting with methods for extracting light roasts (e.g., pressure and flow profiling.) No trouble at all detecting when a shot is under-extracted!

Not that a few measurements wouldn't be useful. I find the refractometer mainly useful for troubleshooting and evaluating equipment, and use my taste buds to evaluate coffee. But in this particular case the refractometer might be helpful in tracking the daily changes in extraction as these ultra light beans age. I'll be able to taste any meaningful changes, but the refractometer can put some numbers on it and the record of the daily results would likely be much more precise than my taste memory.