tag:blogger.com,1999:blog-6377410.post4930734539088693305..comments2023-12-08T04:08:10.835-06:00Comments on Hindered Settling: The science of espresso, with a dash of geologyAnonymoushttp://www.blogger.com/profile/02317685391212630354noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-6377410.post-56010916666766975442009-01-17T16:10:00.000-06:002009-01-17T16:10:00.000-06:00As a geologist myself, I appreciate this perspecti...As a geologist myself, I appreciate this perspective on espresso. Although not something most people would do at home, roasting also is a key aspect, and maybe the writer could say something about how low temperature, slow oxidation reactions alter the materials present in the raw beans, and how the bean also is physically modified, thus changing the way it crushes and fractures during grinding. Roasting rate also is probably important--though I have not done my research on this; you would think that the extent of oxidation as a function of depth within each bean and that is going to be controlled by the period of roasting, the temperature, and supply of oxygen, as well as by the extent to which beans are turned and roasted homogeneously, or instead burned heterogeneously. As a working hypothesis, I'd say that roasting has to be as key as the grinding and leaching processes. And I am sure that coffee growers will have something to say about the environment of growing, flowering, fruiting, and ripening conditions, as well as how the beans are picked and stored until roasting. Fortunately for me, the very best coffee is produced in my daughter's coffee shop, Caffe Adagio, in Bellingham, Washington; the beans are roasted by Cafe d'Arte in Seattle. And the roaster obviously knows how to roast and they presumably know how to get good beans from the best growers. So experts all along the way make my favorite coffee, which I typically sip with a copy of the New York Times; the coffee helps me come to grips with this bad, bad and still wonderful world. Alas, my present cup of coffee in Tucson was brewed by me; either I need more geology of coffee lessons, or I need to make my way back to Bellingham.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6377410.post-21757789915516064742009-01-12T22:28:00.000-06:002009-01-12T22:28:00.000-06:00Brian, I think one could do relatively easily an e...Brian, I think one could do relatively easily an experiment to see how different coffee grain sizes affect the discharge (and coffee taste... I can predict that it's going to be really bad as soon as you use coffee that is just a bit coarser than necessary). You would have to make sure that the same amount of pressure has been applied during tamping. With regards to different types of coffee -- I am not sure, but I think that you tend to get similar grain sizes and shapes if you use a burr grinder, regardless of coffee type. But haven't tested that...<BR/><BR/>Effjot - yepp, I oversimplified when I wrote that "one cannot change the density and viscosity of water". One could some experiments to see how the discharge varies with increasing water temperature... Especially if you have a machine with a good control of temperature.Anonymoushttps://www.blogger.com/profile/02317685391212630354noreply@blogger.comtag:blogger.com,1999:blog-6377410.post-84090122991732128712009-01-11T17:10:00.000-06:002009-01-11T17:10:00.000-06:00Very nice! I always like it when there are everyda...Very nice! I always like it when there are everyday analogs to geological (or other scientific) laws.<BR/><BR/>As me flat mate is an avid espresso maker and drinker, with his own mill, I should perhaps take some coffee grains and sieve them for their size distribution…<BR/><BR/>I think you shouldn't dismiss viscosity so easily (“one cannot change the density and viscosity of water”) . Between 85 and 95 °C it changes by roughly 10%. Probably not so important for the coffee example, but not completly neglible. On the other hand, <I>k</I> values vary more widely, shadowing viscosity and density effects.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6377410.post-48731176882089916332009-01-11T12:11:00.000-06:002009-01-11T12:11:00.000-06:00A post with sedimentology AND coffee automatically...A post with sedimentology AND coffee automatically becomes one of my favorites!<BR/><BR/>Zoltan says: "The most important variable is coffee permeability, which is influenced by size, sorting, and packing (compaction) of the coffee grains."<BR/><BR/>Perhaps one could systematically test the different types of coffee to evaluate variability as a function of coffee grain shape and its impact on sorting? Or, are all the grain shapes the same regardless of coffee type since you grind them yourself?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6377410.post-33707509223867569002009-01-11T10:57:00.000-06:002009-01-11T10:57:00.000-06:00That's a great post. I'm going to have to think ab...That's a great post. I'm going to have to think about an espresso machine!Silver Foxhttps://www.blogger.com/profile/03131032620978696727noreply@blogger.com