Why does the coarseness change with the last coffee beans?

Grinders are one of the keys to exceptional espresso. Discuss them here.
BaristaMcBob
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#1: Post by BaristaMcBob »

I'm using a Ceado E37s. It has 80mm burrs. Not sure whether that info is relevant. Anyway, I have my grind setting dialed in perfectly. However, when I pull a shot using the last of the beans in the hopper, my shot pours way too fast, even though I have the correct weight (17.5g) in the basket.

Is it necessary to keep a minimum amount of beans in the hopper? Anyone else experience this?

Corgo
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#2: Post by Corgo »

Pretty sure for hopper grinders the amount of beans play a role on feeding into the grinder. At near empty, there's not enough weight to push the beans in so if it's a timed grind, you're likely getting less ground out. Do you actually measure how much comes out? I would think if you just make sure output is the same amount of grounds, you should have similar pulls. So I am wonder if the last bit of your beans is actually causing a different dose rather than ground coarseness.

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cafeIKE
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#3: Post by cafeIKE »

BaristaMcBob wrote:Is it necessary to keep a minimum amount of beans in the hopper? Anyone else experience this?
Yup




Patent has run out, so feel free to improvise... 8)

Mat-O-Matic
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#4: Post by Mat-O-Matic »

'Popcorning' is a useful search term to learn more about this. Different grinders are more or less susceptible, with better single dosing grinders designed specifically to avoid it. Also, beans bumping into each other helps grind beans finer, so as fewer beans are in the chamber, the result becomes coarser. There are several solutions for the E37s, and the simplest is to put a tamper in place of the hopper.
LMWDP #716: Spring comes, and the grass grows by itself.

DaveC
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#5: Post by DaveC »

BaristaMcBob wrote:I'm using a Ceado E37s. It has 80mm burrs. Not sure whether that info is relevant. Anyway, I have my grind setting dialed in perfectly. However, when I pull a shot using the last of the beans in the hopper, my shot pours way to fast, even though I have the correct weight (17.5g) in the basket.

Is it necessary to keep a minimum amount of beans in the hopper? Anyone else experience this?
This happens because when the beans flow too fast into flat burrs, a higher proportion grind against themselves, rather than the burrs. I call it "packing". There is an optimum "pack" for flat burrs. Generally because of AC induction motors, the grinders run far too fast for optimum performance and the burrs pack far too much. This creates fines and poor grind quality. Different burr sizes have different optimum speeds for grinding. Sadly none of those speeds are anywhere near a normal AC induction motor and the speeds of burrs in commercial grinders. It is unfortunate that large grinder manufacturers think faster is better...I've told a few, but I think only one or two are hearing me. This was the main reason behind the concept of the Niche flow control disk, not popcorning.

Theoretically you would get a better grind by closing up the burrs and feeding the beans slowly..the problem then of course is the burrs then don't like to feed, because the manufacturers never considered home use and single dosing. This the breaker and feed in zone have a suboptimal cut.

That's my take on it for what it's worth.....

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cafeIKE
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#6: Post by cafeIKE »

Mat-O-Matic wrote:the simplest is to put a tamper in place of the hopper.
Way back I found that not allowing the beans to get below the spindle and a mass equal to approximately ½ hopper height column of beans was about as optimal as optimal gets in espresso.

A tamper is too heavy and on some grinders, about ½ the dose is ground much coarser as the tamper rides atop the spindle.

If one changes beans for every shot, the Niche or other optimized single dose grinder will be necessary.

Acavia
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#7: Post by Acavia »

DaveC wrote:This happens because when the beans flow too fast into flat burrs, a higher proportion grind against themselves, rather than the burrs. I call it "packing". There is an optimum "pack" for flat burrs. Generally because of AC induction motors, the grinders run far too fast for optimum performance and the burrs pack far too much. This creates fines and poor grind quality. Different burr sizes have different optimum speeds for grinding. Sadly none of those speeds are anywhere near a normal AC induction motor and the speeds of burrs in commercial grinders. It is unfortunate that large grinder manufacturers think faster is better...I've told a few, but I think only one or two are hearing me. This was the main reason behind the concept of the Niche flow control disk, not popcorning.

Theoretically you would get a better grind by closing up the burrs and feeding the beans slowly..the problem then of course is the burrs then don't like to feed, because the manufacturers never considered home use and single dosing. This the breaker and feed in zone have a suboptimal cut.

That's my take on it for what it's worth.....
I have Ditting 804, should I pour the beans in very slow? Normally I just dump in my ~23g dose, and all is ground in matter of seconds. Should I pour them more slowly?

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RapidCoffee
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#8: Post by RapidCoffee »

DaveC wrote:This happens because when the beans flow too fast into flat burrs...
This is not only a flat burr phenomenon. Conical burr grinds also shift coarser with no bean load. Single dosing requires a much finer grind setting than grinding with a bean load in the hopper, regardless of burr type.
Acavia wrote:I have Ditting 804, should I pour the beans in very slow? Normally I just dump in my ~23g dose, and all is ground in matter of seconds. Should I pour them more slowly?
If your goal is a more uniform grind, then yes, it makes sense to feed beans slowly when you single dose. But I've never had the patience... :twisted:
John

BaristaMcBob (original poster)
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#9: Post by BaristaMcBob (original poster) »

Wow. Interesting. Okay, I won't let my hopper run on empty. Good to know.

patcof1
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#10: Post by patcof1 »

BaristaMcBob wrote:I'm using a Ceado E37s. It has 80mm burrs. Not sure whether that info is relevant. Anyway, I have my grind setting dialed in perfectly. However, when I pull a shot using the last of the beans in the hopper, my shot pours way too fast, even though I have the correct weight (17.5g) in the basket.
If you simply increase the dose by 1.5g or 2g (without changing the grind setting) only for the shot from the last beans in the hopper, the pour speed of this shot will be approximately the same as the pour speed of previous shots. Of course this will also change the taste somehow. Did you already try this test?

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