Longer pre-infusion for less channeling? - Page 4

Beginner and pro baristas share tips and tricks for making espresso.
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lassepavoni (original poster)
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#31: Post by lassepavoni (original poster) »

No, I don't use RDT and never tried it.

Might as well be that channeling is not my actual problem, but to me it pretty much looks like what I'd expect it to be. Now that I have a bottomless portafilter, I can look out for telltale signs like spritzers and uneven flow.
Regards, Lasse
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lassepavoni (original poster)
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#32: Post by lassepavoni (original poster) »

Got a bag of fresh beans, 60% Arabica, about 2 weeks post roast (did not roast them myself). Pulled some "unscientific" shots to dial in the new beans and, well, have some coffee. Using the bottomless portafilter, I could make the following observation:
Using the new WDT tool with 8 needles of 0.4mm I would get only minor channeling, or maybe even none at all. All of those pulls were pretty spongy though. Didn't have any spongy pulls in a long time, so I tried to verify my suspicion that this must be due to WDT:
Using my DIY WDT tool with 3 needles of 0.9mm I would get visible channeling, with some spritzers and pretty uneven flow, leading to premature blonding. But no sponginess at all; at the end of the shot the lever remained at the lowest position and would not come back up a little.
I pulled four shots, swapping the WDT tool each time, and the behavior was repeatable. Don't know what to make of it right now, but I thought I'd share.
Regards, Lasse
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lassepavoni (original poster)
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#33: Post by lassepavoni (original poster) »

Several failed shots later, the one from today seems noteworthy again. Prior to the puck prep, I modified the new WDT tool a little and removed half of the 8 needles. The remaining four are now effectively a little more spread out than before and thus don't seem to be creating new clumps. This is just an observation with n=1 and might have been an outlier, but the puck prep was somewhat ambitious with 15g in, pretty fine grind setting and a firm tamp. The first 20 or so seconds after the first drops appeared really looked like a video played in slow motion and I had to apply plenty of force to the lever. Pull time was approaching 90 seconds and the lever acted fairly spongy again at the end, but I didn't notice any spritzing at all. The result in the cup was pretty tasty, too! I'd consider this an exemplary puck prep without flaws, even though the grind and/or dose might need some tweaking. I hope the next shots will turn out equally well.

Edit: Tried to upload and share the video on my OwnCloud: http://ablage.preamp.org/index.php/s/NhMv9gj0LDGho4G
Regards, Lasse
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lassepavoni (original poster)
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#34: Post by lassepavoni (original poster) »

Still trying. I guess this thread now has become something like my personal notebook :) - feel free to chime in anytime though.

Today I have made the following observation with an n=2. Using the 0.2mm puck screen, 12g of really dark and oily beans, ground a little coarser than usual, I got severe horizontal channeling. Both shots ran much too quick and were rather blonde right from the start. Not a lot of resistance on the lever. On knocking out the puck afterwards, it would split into two discs horizontally. The upper half came out rather easy, but I had to scrape the lower half out of the basket, because it just would'nt budge. The result in the cup was quite okay, though.

Yesterday I came across this video on YouTube:
After watching his shots, showing what I consider heavy channeling and uneven flow, I think I'm doing not half as bad, actually :o ...
Regards, Lasse
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LittleCoffee
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#35: Post by LittleCoffee »

Here's my 2c having read from the start, but not every word.

I don't think the WDT is your issue. I think the age of your beans is your number one issue. To get the espresso extraction time with 8 week old beans means grinding extremely fine to compensate for the age of the beans. When you grind extremely fine you knock on Mr. Channel's door and say "Come on in, anytime.".

That's why I think you see an improvement with two week old beans, sure maybe the WDT helps, but honestly WDT is not like nuclear physics - it's just some swizzling with needles. It's hard to get it wrong. Personally, I'm also a dark roast fan (albeit arabica) and even two weeks is at the limit - there's a very very noticeable increase in how finely I need to grind my dark roast to extract properly over thefirst 14 days post roast. I don't think dark roast beans are much good past more than day 9-10+.

After that, trying 16g in a Europiccola is doable but is more intermediate/advanced than beginner. Again, like the fineness of the grind, you leave very little room for error before Mr. Channel is welcome any time. Start out with 14g.

The only other factor for variability is your tamping. I don't think you said what you used, but make sure you tamp hard enough but not too hard. Press down on a bathroom scale to get a feel for it.

Good luck.

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lassepavoni (original poster)
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#36: Post by lassepavoni (original poster) »

Thank you for your comments!
LittleCoffee wrote:When you grind extremely fine you knock on Mr. Channel's door and say "Come on in, anytime.".
That's pretty much what I have been suspecting lately, but I haven't attributed it to the age of the beans. But that certainly makes sense. Since I don't like the results of a coarser grind, I should better avoid buying three different bags at once in the future - or drink more coffee :lol:
LittleCoffee wrote:(...) but honestly WDT is not like nuclear physics - it's just some swizzling with needles. It's hard to get it wrong.
Used to think so, too. Until I made a little experiment with a rather surprising outcome. I put the grounds (usual grind size, usual dose) into a whisky glass and applied the usual amount of WDT. From the top down everything looked fine, but watched from the sides through the glass there were a lot of trenches and furrows visible. Even worse, after a straight-down tap on the counter, the grounds did not totally settle to close up all of those channels! So I would say that it is possible to introduce additional channeling using "WDT done wrong".
LittleCoffee wrote:I don't think dark roast beans are much good past more than day 9-10+.
That seems to contradict what I have read so far about dark "italian classic" roasts, which seem to have a much longer shelf life than the medium to light roasts. :?
LittleCoffee wrote:After that, trying 16g in a Europiccola is doable but is more intermediate/advanced than beginner. Again, like the fineness of the grind, you leave very little room for error before Mr. Channel is welcome any time. Start out with 14g.
I have tried everything in the range from 12g to 16g. There are certainly roasts that are much too fluffy to actually fit 16g into the basket, but for others I have found that dose to work better than the lower doses. Might have been true for some older beans though.
LittleCoffee wrote:The only other factor for variability is your tamping. I don't think you said what you used, but make sure you tamp hard enough but not too hard.
I am using a standard aluminum flat based 51.6mm tamper from Coffee Sensor. Having tried everything between a light leveling-only tamp, and leaning on the tamper with the full weight of my upper body, I have already found out that a healthy in-between of those two extremes works best. Too light a tamp makes a muddy mess of the puck, while a hydraulic press tamp seems to fracture the puck and pretty reliably leads to channeling every time.
Regards, Lasse
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lassepavoni (original poster)
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#37: Post by lassepavoni (original poster) »

lassepavoni wrote:Temperature idles around 100°C prior to pulling a shot, rises up to around 106°C during the shot, and then slowly goes down back to around 100°C until I am ready to pull the next shot.
Out of curiosity I have recorded some more temperatures today. This time I used two DS18B20, attached one to the group head, and the other one to the boiler (at the lower end of the sight glass). Started the data logger and proceeded as usual, pulling three shots in total. Those temperatures from the digitally calibrated sensors look somewhat more reasonable than the 100°C+ my multimeter reported last time.

Regards, Lasse
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lassepavoni (original poster)
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#38: Post by lassepavoni (original poster) »

Some more temperature readings, just for the fun of it while the sensors are still hooked up.
Today I put the grouphead sensor from the upper part of the bell down to the lower part of it. With the sensor on the upper part, you can see the start of the pulls through a rise in temperature, while on the lower part, you can see a drop in temperature from locking in the cold portafilter. Overall there's a noticeable difference of ~8°C in measured grouphead temperature.

Regards, Lasse
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