Hi there Guido, It is hard to say if something is wrong. Is it a vibe or rotary pump? What is the pressure achieved when you use the blind PF? Which naked PF are you using?
As an aside, I have a rotary B2, and it takes about 2-3 seconds for pressure to start rising (with the blind PF), and about 5 seconds to reach full pressure. Some drop in the pressure is normal; you have an overpressure protection device of some kind (i.e. the OPV on a vibe or the return on the rotary) and when it opens, etc. it can let pressure change just slightly. In any case, a few thoughts come to mind. First, in my opinion, blonding in some areas and not others is always a problem. Also, any channeling is always a problem. Also, sprays are always a problem, because they mean channeling. You want the shot to emerge all over the PF at once, perhaps just a fraction of a second sooner at the edges, and then it should appear like thick, gloppy syrup. As the shot progresses, the espresso "hangs" like a small tornado that gets longer and wider. As the shot is finishing, the tornado will get smaller (shorter, narrower) and will just look "thin"--this is too long to let the shot go. As soon as the tornado starts to shrink you should be stopping the shot. When you have one part that is blonding early, that means the coffee wasn't distributed well--so one section is less dense than the rest. That section will be over-extracted, and the rest will be correctly extracted, which means bitter/harsh. The same is true for channeling of any kind, although the results will not be as dramatic as with the bad distribution. Read up on the Weiss Technique (http://www.home-barista.com/weiss-distribution-technique.html) and try it. I use it still with every shot, but use a canning funnel instead of a yogurt cup ($10 on ebay for a nice stainless one), and it made my shots better instantly. Perfect evenness every time, but don't overdo the stirring, as some report that drops fines to the bottom of the PF and gives bitterness too. Another factor that affects all this is brew pressure. There have been several reports on this list lately about machines being pre-set to 12 bar, which is way too high. With the blind PF, set your pressure to 9 bar. With coffee, the pressure should then be about 8.5 bar. This is a good starting point; some like to tweak brew pressure a bit later on, but for starting out, this is a reliable and reasonable pressure to use. Another thing would be temperature. If the temperature is too high or too low, it can create espresso that is overly harsh/bitter or really "grassy" or "bright", to a fault. Here again, use a temperature that is known to produce good espresso, and stick with it until you sort out the other problems. Something around 94-96 Celsius is a reasonable temperature for starting out. I use 95 and 96 for almost all blends I extract (204-205 Fahrenheit). Grind certainly plays a role, but you should be able to get a decent extraction with some variance in grind. Try to use the grind that worked in the other machine, and hold that variable steady also. Freshness of coffee also is huge, as defects are magnified with espresso. You might also try volume dosing, i.e. grind full, distribute, and scrape the coffee off the top with your finger before tamping. It is a bigger dose than you're after, but may stop the channeling enough to let you find out if there really is something else going on. If at all possible, find another Expobar owner in your area to come help, or visit them. But, since you're having good luck on the other machine, I would have to guess that there's a setting that needs adjustment. My money is on pressure and/or temperature. Keep us posted on what you find, and talk soon. Ben McCafferty On Mar 23, 2012, at 9:20 AM, guido wrote: > hello, > > i want to add some details to my previous post. > > first that i have a naked portafilter, and have been monitoring channeling. > in the beginning, there was a lot. i was not satisfied with the original > double-basket, it required about 16 grams of coffee to prevent channeling > though a wet puck, so i switched to a slightly smaller one which works best > around 14.2 grams of coffee (depending on the beans used). now there is no > excess channeling. > > my experience with channeling is as follows, too little coffee results in a > wet puck with pinhole in the middle. too much coffee, and i get excessive > side-channeling. there is always a little side-channeling, but it does not > seem any worse than i see in youtube clips of naked-portafilter extraction. > > in the beginning of the shot, there is a little more coffee around the edge > but it's not a proper donut shape and the middle fills in pretty soon. during > the shot, the might be some spot that emit a slightly blonder shade, but it > doesn't seem that bad. and i might see one or two half-seconds sprays, but i > understand these aren't a real problem either? > > i should also add that my brewtus is slow to gain pressure. it takes about 8 > seconds for the pressure to start rising, and then 3 or 4 seconds for the > pressure to reach the maximum. after that, when the coffee has started > flowing, sometimes i see a drop, sometimes as much as .5 bar in pressure. i > am not sure if this is due to decreasing resistance from the coffeebed, or > maybe it is a flaw from the machine? i would love to hear an expert opinion > on this, as well as other peoples experiences. this pressure drop does not > occur when using a blind filter so i don't think the pressure leaks > internally. > > then i want to say i think the problem is the brewtus (or perhaps me and the > brewtus) and now the coffee or grind. if this were the case, i would not be > able to make great espresso with the gaggia, would i? > > if more details are required, please ask. i would be happy to give detailed > information if that could help diagnosing the problem. > > all the best, > guido. > > >> hello everybody, >> >> i am struggeling for some months now to get really great coffee from >> my brewtus iv. the problem is simply explained, the coffee is always >> harsh to some extend. >> >> while i was going through all the variables (beans, grind, dose, tamp, >> temperature, pressure) i did get my hands on a secondhand gaggia >> classic and the latter outperforms my brewtus with ease. that just >> cannot be! :( >> >> i've tried so many combinations, i might just have tried it all. i am >> starting to feel despair. maybe i just got a bad machine. but it's not >> like there is a malfunction that can be shown, i don't think i can >> return it to get a replacement with the argument 'the coffee tastes >> harsh'. the fact that i ordered the machine from france (i live in the >> netherlands) makes this more complicated. >> >> with all the experimenting, i can make it more harsh or less harsh, >> but never really perfect. with the gaggia, that's just simple, find >> the right dose and grind (check flowrate) and you're rewarded with a >> great cup. >> >> with the brewtus, a big financial investment plus months of struggling >> and no reward. >> >> it is in this despair that i am asking this forum for help. >> >> all the best, >> guido. > > -- > You received this message because you are subscribed to the Google Groups > "Brewtus" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/brewtus?hl=en. > -- You received this message because you are subscribed to the Google Groups "Brewtus" group. 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