Posted Fri Oct 18, 2013, 8:40am Subject: Do some Roasters' roasts just channel more than other's?
Problem: Four blend/SO fresh roasts from one roaster company consistently channel a lot. Target responders: CGers with professional or stable prosumer experience, baristas or roasters. Machine: Mypressi Grinder: Compak K10
Details: First, I feel constrained to be an apologist for the Mypressi. I move frequently and cannot tolerate the weight or packing space of even a consumer machine, let alone a plumbed in job. The grinder takes up all of the weight/space that I can afford, which tells you how important it is. The Mypressi is an elegant machine and I have replicated the occasional 'god-shot' that I have had in top-quality cafes around the US. The Mypressi has several touchy points, there is no such thing as heat stability and it is prone to channeling. I usually get channel-free infusions (it can be used in 'naked portafilter' mode) 60% of the time by using fresh beans and watching my technique. Most of the remaining time, channeling is present but minor. If there is one instrument that you want in order to gauge your technique or roast freshness by the phenomenon of channeling, the Mypressi is it.
Four months ago I relocated once again and, as usual, I started buying from local roasters. Most have been dropped for lack of quality but there is one quality roaster locally with a good reputation and I have bought six pounds at various times, four different roasts, from them. I have had very good shots from their roasts in area cafes and at the coffee bar they have at the entrance to their roastery.
Trouble is, their roasts always channel to some extent, somtimes horribly, no matter how much attention is spent in dialing them in. They are bought from one day to six days after roasting, mostly three days. They have produced more sink shots in the past four months than I have produced in the previous two and one-half years. When I travel OOT and return with some else's fresh roasts, channeling goes down to baseline.
I cannot help but conclude that there is something about this roaster's coffee that causes more channeling than others. I am looking for experienced CGers who have had a similar experience...or is this some well-known phenom I have never heard about?
Posted Sun Oct 20, 2013, 8:31am Subject: Re: Do some Roasters' roasts just channel more than other's?
I agree to an extent. Does your prep technique require hitting the basket at all? Light roasts I find when knocked just loosen up and can be fixed with a second prep and tamp, mediums I almost never have a problem with. Dark roasts pack nice ant tight but if knocked at all will create a huge crack in the puck.. Personally I don't think it can ever be the bean. Have yo tried pre infusing/wetting your puck before locking it in?
Posted Sun Oct 20, 2013, 9:06am Subject: Re: Do some Roasters' roasts just channel more than other's?
Yes, that is what I am asking ... can it ever be the bean...?
Concerning portafilter impact: Mypressi has baskets that are filled and tamped before being inserted into the ring - unlike a portafilter. I advise Mypressi newbies not to drop the tamped, filled basket into the ring with a !clunk! for the reason you suggested.
Anyway, the occurrence happened between periods of other roasters beans acting normally, like an A-B-A research design, which confounds technique as the culprit. I always suspect my technique first, including how I grind the bean (not just fineness but bean and grinder temperature (AC or no AC) and can't find any cause...so far.
Posted Tue Oct 22, 2013, 11:57am Subject: Re: Do some Roasters' roasts just channel more than other's?
Have you considered the blending methods the roasters employ? In my experience, the flow rate of espresso and pourovers in some isntances was highly variable on the degree of roast and original screen size of the beans. For instance, blending a large screen indian coffee (a popular thing to do in commercial espresso blends) with a smaller dry processed brazilian coffee would make a real mess of our espresso machine if we used a bottomless portafilter. I liked to attribute this to the varying densities of each particle that comes out of the grinder... each particle is a different density. This is easy to see--just weight the same amount of two roasts (one dark and one light). The darker one will occupy more volume of the same origin bean. As for the screen size.. try finding two screen size beans and do just the same. Weigh two amounts of the same roast but different screen size and you will see the difference in space it occupies. When a roaster overlooks screen size and rate at which different beans roast (things like bean moisture content play in here), you inevitably run the risk of varying density particles when you grind and dose into a portafilter. This (from what I conclude) means when the water flows through it will find the pockets with least resistance and channel because there are so many variable particle sizes and densities. Another thing--when the grounds become saturated with water they tend to expand. I'm sure this along with fat content and a whole host of other things comes into play with channeling.
Not sure if that helps but just a scatter of my thoughts. I spent a few months this year trying to develop an espresso blend that suited my tastes (sugar bomb with a slight liveliness on the tongue with a clean finish). I got close but never did quite nail it. I'm thoroughly impressed with roasters who can develop an excellent blend that tastes good and performs well. I also like if they can offer it green and I can achieve similar results (I trust my roasting and brewing, but not my blending).
Posted Tue Oct 22, 2013, 1:52pm Subject: Re: Do some Roasters' roasts just channel more than other's?
I never could figure out how SM's green blends work out in the roaster since different beans roast at different rates. I guess not that different in rates. That is what is keeping me from roasting their blends. I just buy their SO. I cannot roast this year since I am in a highrise.
Different particle size may not be bad for packing. There is a concept is crystallography and other brances of chemistry called Closest Packing Arrangement. The packing usually improves when more than one size is present. Think of the hardness of steel when carbon is present in iron. I am thinking that no one knows the whys of channeling - we just know operationally what makes it more likely or less likely. Your density argument is understandable. You have made me think that I might call up their roaster, whom I have met, and ask him! Duh.
weebit_nutty Senior Member Joined: 26 Sep 2013 Posts: 212 Location: Los Angeles Expertise: I love coffee
Posted Thu Oct 24, 2013, 4:01pm Subject: Re: Do some Roasters' roasts just channel more than other's?
Do some roasters roasts just channel more than others?
They shouldn't so long as the roasts are delivered within the same parameters, such as roast date, roast profiles, and humidity (resulting moisture level in the beans). But of course that never happens between different roasters. They all have variations in their processes means you can never be sure your current settings will work until you try. And more often then not, you have to make adjustments along the way. That's the job of the barista. If all roasts came with the exact same consistency, there would be no need for such a skill set. Channeling is avoided by tuning the grind, tamp, pressures, etc. Of course the process of tuning will requires you to pull shots, often the first ones will be off or downright bad. It's all expected when changing coffees. In fact, even between different batches of the same coffee from the same supplier you may need to make adjustments. Heck.. Even through out the day, the with the same exact batch, with temp and humidity swings, you will need to make changes. Every pro-barista knows this.
If you don't want to deal with frequent channeling, don't switch beans so often. Stick with one reliable supplier that maintains consistency in the parameters of the coffee they provide. If you want to use multiple suppliers, you will need to tune and record your parameters for each coffee, so that your shots may be repeated between coffee swaps.
One note about the OP's comment on the MyPressi. As an avid user of this brilliant device, I would have to adamantly disagree with the suggestion that it is prone to channeling and that there is no such thing as heat stability. Well, actually the latter may be true in the sense that the device offers no automated say to maintain a consistent stable temperature, but ultimatley, it is very capable of pulling a shot at an optimal temperature. The only catch is it doing so is entirely in your hands. From my experience, I have tuned my workflow to consistently pull shots at optimal extraction temperatures. The beauty is not only in the shot, but the credit goes to me for doing the work, which makes the drink all the more satisfying. And the assertion about the channeling. I'm sorry but that is entirely again user error. While channeling is often the result of poor grind and tamp, I do agree the machine *can* have a role in this. I find that my Olympia Cremina is far less forgiving than the MyPressi Twist. The MyPressi Twist has an engineered measurement of waterflow from the showerhead to the basket that provides a very soft gentle introduction of water onto the puck. I see this whenever I empty the basket. The used puck is beautiful...Virtually unadultered and steaming dry. On my Cremina, has never once produce such a lovely puck. When bad, channeled shots happen, the puck looks like sh*t, full of craters, as if it was blasted by a garden hose. That is the difficulty with lever machines. The water is under high steam pressure, and you only have a millimeter or two of play between zero flow and a full blast of steaming hot water at over a bar of pressure. But that, too, is the beauty of manual lever machines--you are in control.
Anyway I don't want to further digress. Just thought I should respond in defense of my favorite espresso extraction method. As I mentioned, while I do have a Onlympia Cremina I have yet to pull as great a shot on it as I have on my MyPressi Twist. Of course I need to improve my skills. But I suppose one could say that is the entire point of owning such a machine.
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