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> Coffee Lover v.2 Thread, Let's Share!

ymeng85
post Sep 17 2018, 08:39 PM

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QUOTE(mrl @ Sep 17 2018, 07:58 PM)
I have one question.

Currently I have 2 type of beans, Starbucks Ethiopia Sidamo and Reframe's Yirg... The Starbucks' is roasted super dark, I don't know what to do with it other than mix it with milk. The Yirg on the other hand is a lot lighter.

What happened is that, the super dark Starbucks' beans is grinded pretty easily that I have to use 7-8 steps from the finest on my grinder. While for the lighter yirg, I had to force it through 1 step from finest on my grinder.

How can that happen?
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And just curious, was the Yirg ok for you? tongue.gif
mrl
post Sep 17 2018, 09:03 PM

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QUOTE(kuluuluk @ Sep 17 2018, 08:07 PM)
Maybe I should've mentioned that, the super dark roast extracts 30ml in 30sec with 7-8 clicks, while the lighter one does 1 click. That's what I am scratching my head right now. I see the article only says the the finer it goes, more surface area that leads to more extraction. But what I'm confused is that, why does lighter one needs finer setting than the dark to get the same thing? Touching the grounds, I can really feel the difference. Shouldn't the gap between static and rotating burr should be the same regardless of roast level?

Thanks for the article though, been scratching my head the keyword to google the thing.

QUOTE(ymeng85 @ Sep 17 2018, 08:39 PM)
And just curious, was the Yirg ok for you?  tongue.gif
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It is the most awesome cup of coffee I have ever had. Even if I screw up a shot, it doesn't even ruin my americano.

ymeng85
post Sep 17 2018, 09:11 PM

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QUOTE(mrl @ Sep 17 2018, 09:03 PM)
Maybe I should've mentioned that, the super dark roast extracts 30ml in 30sec with 7-8 clicks, while the lighter one does 1 click. That's what I am scratching my head right now. I see the article only says the the finer it goes, more surface area that leads to more extraction. But what I'm confused is that, why does lighter one needs finer setting than the dark to get the same thing? Touching the grounds, I can really feel the difference. Shouldn't the gap between static and rotating burr should be the same regardless of roast level?

Thanks for the article though, been scratching my head the keyword to google the thing.
It is the most awesome cup of coffee I have ever had. Even if I screw up a shot, it doesn't even ruin my americano.
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Thanks. Super happy to hear that! biggrin.gif

Its due to the porosity of the coffee. A darker roast has a more expanded cell wall structure which makes it more water absorbent compared to a light roast. And with absorption, you will also observe puck swelling, further closing down all water channels.

You can almost compare this to like passing water through flour vs through sand. At the same particle size, the flour would be exponentially more resistant to water flow
kuluuluk
post Sep 17 2018, 09:33 PM

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QUOTE(ymeng85 @ Sep 17 2018, 09:11 PM)
Thanks. Super happy to hear that!  biggrin.gif

Its due to the porosity of the coffee. A darker roast has a more expanded cell wall structure which makes it more water absorbent compared to a light roast. And with absorption, you will also observe puck swelling, further closing down all water channels.

You can almost compare this to like passing water through flour vs through sand. At the same particle size, the flour would be exponentially more resistant to water flow
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My very simple explanation to him would be the density of light, mid and dark roast stage. If you see green coffee beans, they are very dense/hard but as you roast them, they expands and the more it expands, the less density of the wall structure.


My 2 cents works? mega_shok.gif
mrl
post Sep 17 2018, 09:50 PM

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QUOTE(ymeng85 @ Sep 17 2018, 09:11 PM)
You can almost compare this to like passing water through flour vs through sand. At the same particle size, the flour would be exponentially more resistant to water flow
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So, basically what you're saying is with 7 clicks my grinder produce flour with dark roast and sand with light roast because of the density of the beans?

That's what I'm confused right now, how come that happened with the same gap between two burrs? At this rate, I think I need high speed cam to explain this laugh.gif
rytopa
post Sep 17 2018, 10:23 PM

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QUOTE(mrl @ Sep 17 2018, 09:50 PM)
So, basically what you're saying is with 7 clicks my grinder produce flour with dark roast and sand with light roast because of the density of the beans?

That's what I'm confused right now, how come that happened with the same gap between two burrs? At this rate, I think I need high speed cam to explain this  laugh.gif
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Another way of looking at dark vs light roast is the way the beans behave during grinding.

Darker roast beans are more brittle vs ligther roast. That why it's so much easier to grind dark roast compared to light roast.. when the beans are brittle they shatter more easily leading to more fines production as compared to lighter roast. So you have to grind much finer for the lighter roast to increase the fines to have a comparable flow rate vs the darker roast.


ymeng85
post Yesterday, 09:58 AM

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QUOTE(mrl @ Sep 17 2018, 09:50 PM)
So, basically what you're saying is with 7 clicks my grinder produce flour with dark roast and sand with light roast because of the density of the beans?

That's what I'm confused right now, how come that happened with the same gap between two burrs? At this rate, I think I need high speed cam to explain this  laugh.gif
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Nono...haha
I'm saying you have same size coming out from the grinder. But darker roasts has a less dense cell wall structure on the microscopic level
So it will absorb more water when brewed compared to a light roast. It's going to cause a longer brew time

To hit the same espresso yield with the same amount of time, you will need a coarser grind on a darker roast to compensate

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