I also did this picture of fines .... Or rather; the fraction from the Kruve sifter below 400 um.

I didn't post this photo at first because I doubted how fair/true is was to a brew situation. This is made of fine grind in a cupping cup and then just enough water to mix it up (like 1-2 cm). And then let it sit for a while. Afterwards I wondered if cool so quickly that particles didn't swell up as much as in the brew process.

Anyway, for what it is ... here is a spectrum of the smaller particles ... clearly a difference between those around 300-400 um and the smallest, probably below 100 um. The smallest looks a somewhat disolved. But whether they are gel-like or ???

Almico wrote: I do get a mud layer pouring the same way into my Chemex with grinds from my R120. Can't figure out why.

Could I ask you to stir the dry grind next time you brew this ? To see if it reduces the mud layer ... the point being if there is any separate fines then stir to mix them onto the larger particles.

That is; stir the dry grind before adding it to the filter.

I will do that.

I noticed something this morning that leads me to believe that what I have been experiencing with my Chexex brew is not really a mud later, but perhaps carbon dioxide bubbles colored with fines. It looks like a mud layer until I poke it. Just below the layer of foam are normal size grounds. Even the grounds that stuck to my finger were normal size grounds, not fines.

Navigate wrote:I also did this picture of fines .... Or rather; the fraction from the Kruve sifter below 400 um.

I didn't post this photo at first because I doubted how fair/true is was to a brew situation. This is made of fine grind in a cupping cup and then just enough water to mix it up (like 1-2 cm). And then let it sit for a while. Afterwards I wondered if cool so quickly that particles didn't swell up as much as in the brew process.

Anyway, for what it is ... here is a spectrum of the smaller particles ... clearly a difference between those around 300-400 um and the smallest, probably below 100 um. The smallest looks a somewhat disolved. But whether they are gel-like or ???

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I wonder about the color of the fines... While most are yellow, some have really brown centers. Does it mean the brown center was not extracted (unlike yellow centers which would be extracted)?

One is tempted to deduce that the color of fully extracted coffee - may be a dark yellow - and not brown - brown indicating that there are solubles that avoided being extracted. Does anyone know what is the color of instant coffee manufacturing waste (the leftover 70% of the overextracted coffee)?

AssafL wrote:I wonder about the color of the fines... While most are yellow, some have really brown centers. Does it mean the brown center was not extracted (unlike yellow centers which would be extracted)?

I would venture a guess that they are all the same color, the darker ones are just bigger, therefore appear darker...like looking at a glass table from the edge.

Possible - but this looks like a different color - not a color depth.

The color is reminiscent of sucrose: It doesn't look like a scatter of pure Demerara sugar (varying depth of yellow color) - it looks like a mix of Demerara and Moscavado sugars. Moscavado being brown instead of yellow due to brown impurities (aka molasses).

I also wonder if it could be more than just the thickness of the particles - that makes the difference of the yellow/very light particles versus the brown ones.

As I speculated back in post #19 in this thread:

Navigate wrote:What I found the most interesting of the wet grinds so far is; to see what the separated fines looks like. They look like totally dissolved into a gel. No longer a dark cellulose core.

This makes me speculate: could it be the "dark cellulose part" that holds back the unwanted over-extracted taste ? So it's only when we got this fines-to-fines alone that we get the bad over-extracted taste ? Just speculation.

It make perfectly sense that we don't extract every single bit in the larger particles. We only want to extract up till a certain limit, beyond that point we start extracting undesirable notes/flavours from the coffee, like the undesirable flavours we do get from smaller particles, these tend to have a very undesirable ill tasting bitternes, sometimes dry and ash like.

It would be intresting to see a picture of very overextracted grinds to see if there is a difference.

Yes look allot like molasses

I would suspect that if it indeed where the thickness of the particles, then the color should have been another kind of deeper yellow, but that is not the case

Navigate wrote:Yeah, the "thing" in the center of the red circle here is more of a viscous fluid than a solid gel.

Yes, more investigation is needed. Just hard to look at it under actual brew-conditions with a microscope.

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At high magnification, water will appear viscous because of the surface tension, will it not?

Chaff would show up as different colors.