What about "overdosing" makes channeling more likely? - Page 2

Beginner and pro baristas share tips and tricks for making espresso.
Ken Fox

#11: Post by Ken Fox »

Jasper wrote:This looks contradictory to me, because a typical italian roast is darker than the roast i've seen in N. America.

Illy writes also in The Chemistry of Quality, § 7.5.1, that "Minimum Values (5 gram of coffee per cup)..... ..... are only barely tolerable when dark roasted coffee is used, for it has a higher content of soluble substances."

Greets from Jasper
(barista for Kimbo, dark coffee from Naples :D )
N. American roasting styles are all over the map. If you look at the bottom end, e.g. factory roasted pre-ground products such as Maxwell House, Folgers, et. al, you have a very light roasting style however the raw ingredients are mostly cheap robusta that has been treated to remove the rubber like taste and smell. I think it is fair to say that even though the great majority of coffee sold in the USA is like this, that very few participants on this board are interested in this sort of coffee.

If you instead look at the coffee that is being used in marquee cafes in N. America, you will find it is considerably darker roasted than the above. It isn't just the degree of roast that is important, it is the coffee selected that goes into various blends. If you are blending based upon test shots of 19g size, you are going to come up with different sorts of blends than you would at lower doses.
Merlino wrote:I don't however think that a darker roast benefits from a higher dose per sé, I think it depends on the dose vs the supposed size of the basket. For example, I get better extractions when I dose 18gr into a 21gr basket than I would with a 21gr dose. I think this has to do with the extra headspace which my Silvia is always in dire need of :D
Mostly you refer to my "issue/problem #1," which is going to be machine dependent. What I am talking about is the TASTE that you get in the end product, hopefully a straight espresso so that you can really taste and evaluate it (putting the espresso in milk, for these purposes, will render your observations difficult or impossible).

Try this experiment at home, if you have the interest. Take a single varietal coffee that is capable of making a good espresso (check out http://www.coffeecuppers.com if you need suggestions). Roast one batch into 2nd crack, to the point where you see tiny oil droplets on some beans, then stop the roast. As the beans cool, the scattered oil droplets will resorb into the beans, the roast level will be similar to what is used in most marquee cafes. Roast the other batch through most of first crack but not to the beginning of 2nd crack. After a suitable rest period of 3-5 days, try each coffee in carefully weighed, properly ground, doses at around 14g vs. 18 or 19 g.

I think you will find that the more lightly roasted coffee is undrinkable at the higher dose, but at the lower dose it will display varietal flavors that will be lost in the more darkly roasted version, regardless of the dose you use. The darker roasted version may very well taste better to you in the larger dose, especially if this is the sort of roast level and dosing you are used to.

In the end, you will end up doing whatever it is that gives you the most pleasure. I'm discovering a new universe of flavors in more lightly roasted coffee, than I used to get when I roasted darker and/or bought more darkly roasted blends. Jim Schulman, to whom I attribute a lot of the interest in this approach, began roasting and dosing lighter in an attempt to be able to use more single origin coffees for espresso than prior experience had allowed at the higher doses and roast levels.

Another issue worthy of consideration is waste. If you can make an espresso that is just as good (or better, in my view) by roasting and dosing lighter, what is the argument for roasting darker and dosing heavier? You will have to make this decision for yourself. In the absence of "proof" that convinces you personally, what is the argument in favor of using 35% more coffee, in a manner that requires a lot more effort (distribution, tamping, WDT, whatever) if the result is no better than what you can do more easily and with markedly reduced coffee usage?

Food for thought.

ken
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ericpmoss (original poster)

#12: Post by ericpmoss (original poster) »

timo888 wrote:Based on the following observations, I have some doubts about the "fractured puck" theory: I sometimes pull a shot without any tamp whatsoever -- the surface is already "fractured", and there's plenty of head-space so the screen is not compacting the coffee grounds -- and no channeling occurs if the coffee has been given time to swell adequately under the gentler pressure of preinfusion, before pressure ramps up.

Regards
Timo
Hmmm, here's a thought to test.

w/o a tamp, the surface may be 'fractured', but uniform in density. Then, as long as there is headroom to allow a gentle ramp-up in pressure, no one path through the puck-to-be is preferred over another, as there would be with a tamped, fractured puck. Maybe that gives the grounds a chance to swell into a solid puck and behave as a uniform filter.

What happens if one 'overdoses' w/o a tamp, letting the screen do the tamping? Might that also work, just because it's not fracturing an existing puck but forming one on-the-fly?

Eric
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Merlino

#13: Post by Merlino »

Ken Fox wrote: Try this experiment at home, if you have the interest. Take a single varietal coffee that is capable of making a good espresso (check out http://www.coffeecuppers.com if you need suggestions). Roast one batch into 2nd crack, to the point where you see tiny oil droplets on some beans, then stop the roast. As the beans cool, the scattered oil droplets will resorb into the beans, the roast level will be similar to what is used in most marquee cafes. Roast the other batch through most of first crack but not to the beginning of 2nd crack. After a suitable rest period of 3-5 days, try each coffee in carefully weighed, properly ground, doses at around 14g vs. 18 or 19 g.
Will try! Sorry for not responding to your PM, been feeling a bit under the weather lately. Thanks for the response, though!

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timo888

#14: Post by timo888 »

ericpmoss wrote:... w/o a tamp, the surface may be 'fractured', but uniform in density.
Yes. With a good grinder, chances are better. Giving the basket rim some quick chops with the edge of the spoon handle helps to settle the ground coffee in the basket and can improve the uniformity of the distribution.
ericpmoss wrote: ... What happens if one 'overdoses' w/o a tamp, letting the screen do the tamping? Might that also work, just because it's not fracturing an existing puck but forming one on-the-fly?
A tamped puck is a tamped puck -- the water does not see it as having happened "on the fly". The grounds are already compacted as the water arrives. The water is tamp-method agnostic. So, you still have a taller column of medium which has been more-or-less compacted -- by the tamper or by the dispersion screen-- though the screen probably compacts the coffee grounds less than a tamper does, lowering the chances that channeling will occur (i.e. vis-a-vis the chances with a heavy tamp -- not advocating overdosing here).

Compaction becomes less dense the deeper in the basket you go. If the top of the basket is very compacted (as can happen with overdosing), this can cause the pressure to ramp up above 9 bar (to the OPV crack point, if applicable) and at some point as the pressure rises, either the seal to the basket wall or some cavity or less dense region deeper in the puck presents itself as a path of lesser resistance, and the gush occurs. It stands to reason that the damage the gush causes to the puck is probably proportional to the pressure-level at the time of the gush.

Regards
Timo