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dsc
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Post subject: extraction issues
 Posted: Jun 15, 2009 - 10:06 PM
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Joined: Feb 02, 2007
Posts: 1685
Location: Leatherhead, UK / Gdansk, Poland
Status: Offline
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Hi everyone,
for the last few months my shots were far from perfect, no matter what beans I used. I can taste it in my espressos and in my cappas, too much bitterness, not enough sweetness, lacking body, uneven extractions, early blonding. I've been trying to nail what the reason is but so far I've been unable to, so perhaps someone here will have some suggestions.
Stuff that's not right:
- I usually shot for ristrettos as normal shots (around 50ml) are too fast and go sideways very quickly, something like this happens:
http://www.vimeo.com/2707578
the cone dances around, you can clearly see signs of chanelling and what nots
- when pulling tighter shots it starts well, but usually ends badly. I can only get a small cone to form as it doesn't want to 'grow' as the shot progresses (normally you get a small thin stream which gets bigger and then goes small again near the end of the shot)
- I get a lot of channelling, sprites around the basket, small gaps here and there forming even when the shot starts properly
- taste-wise the shots are not awesome, sometimes I get an odd shot which actually tastes nice, but usually it's too bitter and that overwhelms the rest
Typical shot looks a bit like this, although the few I had today were even worse:
http://www.vimeo.com/4497379
My technique is something like this:
- grind straight to the basket
- I usually keep the dose around 14-16g, not more
- tap the PF on the PF fork (or not I've tried both) and tamp usually light, but I tried medium and hard tamps as well
- cool the HX, lock and go
- I tend to use 3s preinfusion with 0.8bar pressure (water line pressure)
Yes I tried various distribution methods, including my needle tool, although I haven't tried proper WDT (with a thin needle). To be honest it hasn't changed much and I'd rather leave it out and try to keep it as simple as possible. I don't get too many clumps from my Major, perhaps a few from time to time, but usually quite small.
To be honest I'm annoyed to say the least. Not being able to pull a good shot for months is slowly moving me towards drip/PF (which isn't bad). I already sometimes ignore the machine altogether and simply pull out my drip cone as I know the results will probably be better.
If anyone has any suggestions feel free to shoot, I can record more videos and try pretty much anything (Although I will have to order some beans for this de-bugging).
Regards,
dsc. |
_________________
"This week I are mostly...nothing..."
Mahlkonig Guatemala for FP/drip, Elektra T1 + Mazzer Major for espresso
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kingseven
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Post subject: RE: extraction issues
Posted: Jun 15, 2009 - 10:21 PM
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Joined: Feb 24, 2004
Posts: 2096
Location: London
Status: Offline
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Can you shoot some video of the water coming out of the dispersion screen? I have never seen that kind of channeling before that you have in the first video - the way the channels move around like that is crazy. To me it implies that the coffee bed isn't at fault. If it was the channel would be in one spot. This makes me think it might be the way the water is coming in contact with the puck.
The way the water goes through your coffee at the start is also strange. The guys at Arduino believe that preinfusion is only complete when the entire cake is soaked through - then you apply pressure. It looks like you aren't completely preinfusing before brewing. The liquid appears surprisingly quick from the holes in the basket - I would usually expect a little 'ooze' first. Will try and shoot some video of a naked shot on the Synesso. |
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http://www.jimseven.com
I'll never own too many items with which to enjoy coffee.
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syscrusher
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Post subject: RE: extraction issues
Posted: Jun 15, 2009 - 10:26 PM
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Joined: May 27, 2008
Posts: 449
Location: Dublin, Ireland
Status: Offline
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I've seen that kinda thing before, had similar stuff happening on my old Oscar I think.
I think it happened less frequently when I moved from a straight walled basket to a tapered basket.
Never was fully sure as to the cause though, just figured less that perfect distribution.
I'm assuming also your brew pressure is in the 8.5 - 9 bar range.
Agree with Jim that the initial emergence appears to be very rapid, looks like it's going to be a gusher, then calms down. |
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Last edited by syscrusher on Jun 15, 2009 - 10:28 PM; edited 1 time in total
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kingseven
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Post subject: RE: extraction issues
Posted: Jun 15, 2009 - 10:27 PM
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Joined: Feb 24, 2004
Posts: 2096
Location: London
Status: Offline
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| Oh - and can you weigh a finished espresso (excluding cup obviously) |
_________________
http://www.jimseven.com
I'll never own too many items with which to enjoy coffee.
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dsc
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Post subject: RE: extraction issues
Posted: Jun 15, 2009 - 11:26 PM
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Joined: Feb 02, 2007
Posts: 1685
Location: Leatherhead, UK / Gdansk, Poland
Status: Offline
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Hi guys,
thanks for the replies.
Water output from the group is something quite strange on this machine, both annoying and stupid. Here's a short video showing how wild the group is when woken up:
http://vimeo.com/2379514
(not working at the moment dunno why)
I know it's not what you wanted James, but here's a short description:
- when flushing from idle the water goes everywhere, literally everywhere, on your hands, the counter in front of the machine, the front machine panel, grinder standing next to the machine and so on
- after a while is calms down, but the stream isn't steady, it tends to move around as well, a bit like those light patches during the extraction
- if you are interested in how the group is built have a look at this photo:
there's a dispersion disk with some holes and the screen that covers it.
[NOTE: this is an old picture showing the group straight after I bought the machine, so it's not that dirty now:)]
I was actually thinking of changing the design and using something similar to LMs double-drilled screw, but heard it probably won't change too much. I will shoot the vid tomorrow and weigh the shot.
Forgot to add the pressure is around 8.6-8.7bar. I can try preinfusing longer or not preinfuse at all and see if it makes a difference. I was also surprised to see the shot coming out quickly and then slowing down.
Regards,
dsc. |
_________________
"This week I are mostly...nothing..."
Mahlkonig Guatemala for FP/drip, Elektra T1 + Mazzer Major for espresso
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DrTom
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Post subject: RE: extraction issues
Posted: Jun 16, 2009 - 01:51 AM
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Joined: Aug 27, 2008
Posts: 395
Location: NE UK
Status: Offline
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Hello dsc, it's a real shame to hear 
Have you tried over-dosing your basket? I know this sounds crazy but for a double I weigh out 22 g. If I weigh out the 'specified' 17 g or so, my shot will turn out 'fast' - early blonding, channeling, dancing stream. This is not on a machine as nice as yours, it's a Gaggia classic adjusted to 9 bar with a naked pf and double basket. Although this is also true when I use my Rancilio Z9. No matter what I do with the grind this is what I must do. Good luck with your quest, there is no doubt you will come to a perfect result  |
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GreenBean
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Post subject:
Posted: Jun 16, 2009 - 09:49 AM
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Joined: Jan 03, 2007
Posts: 1037
Location: Chester UK
Status: Offline
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Wow, that does look strange. I have a few thoughts that you have probably already considered and discounted but I will mention them just in case.
I wonder if too much water flow is bypassing the shower screen causing a curtain of water around the edge of the screen to hit the puck. You obviously want the vast majority of the water to flow through the screen not around it.
Have you tried a new shower screen? Is the inner face of the shower screen clean and flat, the outside edge smooth and the recessed corner of the dispersion block (the screen fits into) clean and smooth? When the shower screen is placed on the dispersion block do you have a few millimetres gap at the centre seating so that, when the centre bolt is tightened, it tensions the screen helping it to seal in the recessed corner?
From the photo it looks as though the outside edge of the dispersion block is not sealed by the group head gasket. If this is the case have you checked that you have a good seat between the dispersion block and the group head?
Whatever the problem I hope you get it sorted soon it must be very frustrating. |
_________________
Izzo Alex Duetto | Gaggia XD 2 Group | Mazzer Super Jolly | La Cimbali Max | Solis 166 | Hottop P | Hottop B | French Press (several) | Aeropress (collecting dust) | Kettle modded, no really, added digital thermometer |
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Apex
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Post subject:
Posted: Jun 16, 2009 - 10:40 AM
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Joined: Aug 04, 2008
Posts: 21
Location: Ireland
Status: Offline
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I can't see those vids or pictures at the moment, they're blocked here. I'll check them out later though.
When did you last descale and/or backflush? What's the water like that you're using? Have you opened up the shower screen to take a look? |
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darrensandford
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Post subject:
Posted: Jun 16, 2009 - 11:27 AM
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Joined: Feb 21, 2008
Posts: 333
Location: Coventry, UK
Status: Offline
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| Is it possible (without burning yourself, of course!) to get a shot of the water coming from the group but from underneath, showing the shower screen? It might have to be from a distance, given that spray though. |
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Carl
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Post subject:
Posted: Jun 16, 2009 - 12:27 PM
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Joined: Jan 26, 2009
Posts: 85
Location: Middlesex, UK
Status: Offline
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Weird how it comes through SO fast as soon as the pump comes on. Grasping at straws, if I were tasked with replicating this initial behaviour, I think I might try starting off with a very wet, almost runny puck of coffee grounds in the basket, then applying the pump pressure suddenly.
I note: 1) not overdosing, 2) low pressure (non-progressive?) preinfusion, 3) light tamp. Combined with an aggressive shower, could this combination produce soup in the basket?
How much headspace is there between coffee and showerscreen and does the puck expand to fill the void, (leaving a clean imprint of the screen on the top of the spent puck?) |
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dsc
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Post subject:
Posted: Jun 16, 2009 - 12:40 PM
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Joined: Feb 02, 2007
Posts: 1685
Location: Leatherhead, UK / Gdansk, Poland
Status: Offline
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Hi guys,
ok so here's a couple of answers:
- yes I did try overdosing but the results weren't very promising. I can do a video showing a low dose vs. high dose if needed though (btw. I had a Gaggia Classic a while ago and it's a nice machine:))
- to be honest I don't really like how the dispersion screen is fitted. It's held by a single screw which goes in the middle and presses the screen against the block. It also presses the fine mesh of the screen against the metal backplate of the screen (the one with the bigger holes, you can see it when looking at the back of the shower screen). The problem with that is when the water passes through the shower screen it first hits the metal backplate, deflects a bit or changes the angle at which it flows and hits the mesh straight underneath it. This causes the water to exit at strange angles and doesn't really work well. My way around this was to stick a thin copper wire between the mesh and the metal backplate which lowered the amount of water going sideways simply by allowing more space for the water before it hits the mesh. It is reversible so if you want I can remove it and see if it changes anything. Currently the screw is tightened quite hard and it definitely presses the outside edge of the screen against the block. The dispersion block sits properly against the group 'bell'
- last descale was when I was putting the machine back together, so around a year ago. Quite a while back, but I used it with a filter/softner and judging by the group mushroom there's not much scale build-up. Last backflush yesterday and around a week before that.
- I will take off the hole shower screen/dispersion block combo and take photos and vids. Without the shower screen the water exits the group really fast and looks a bit like a Karcher (pressure washer)
- remember this is not a e61 machine and not a vibe, there's no preinfusion chamber and the ramp up of pressure is very fast, so don't be surprised to see beading very quickly (still it is a bit too fast sometimes). I will try to turn off the preinfusion at inline pressure and see if it helps (although I know people on HB who used it and it didn't do any harm). I do leave a fair bit of space above the puck as I've read Elektra like to have that. Dunno why, but I can experiment, I just need more beans.
Will update the topic today.
Regards,
dsc. |
_________________
"This week I are mostly...nothing..."
Mahlkonig Guatemala for FP/drip, Elektra T1 + Mazzer Major for espresso
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DrTom
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Post subject:
Posted: Jun 16, 2009 - 02:05 PM
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Joined: Aug 27, 2008
Posts: 395
Location: NE UK
Status: Offline
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| Hello dsc, I'm sure a vid won't be needed, it was just an idea - good luck with it I can only imagine the frustration... |
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Carl
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Post subject:
Posted: Jun 16, 2009 - 05:11 PM
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Joined: Jan 26, 2009
Posts: 85
Location: Middlesex, UK
Status: Offline
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| Hi dsc, Another (probably daft) thought: What is the size of the flow restricting nozzle (gicleur) on the Elektra? It almost looks as if it might be missing (!) given the speed with which the water seems to gush out. |
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dsc
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Post subject:
Posted: Jun 17, 2009 - 12:18 AM
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Joined: Feb 02, 2007
Posts: 1685
Location: Leatherhead, UK / Gdansk, Poland
Status: Offline
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Hi guys,
here's a bunch of vids:
- shower screen taken off:
http://www.vimeo.com/5192572
you could probably wash dishes underneath it
- shower screen on, someone who thought this design was good is seriously mentally ill
http://www.vimeo.com/5192672
Finally, below is the shot. Downdosed as suggested by a few people, 14.5g double, no preinfusion. The pour on the video is far from perfect but way better then the previous ones. I pulled three shots before I finally made a vid and they were all good, both look and taste wise.
http://www.vimeo.com/5192809
Guess I found the problem...
Regards,
dsc.
NOTE: the vids are still being processed at the moment so probably won't be available till 1.00am |
_________________
"This week I are mostly...nothing..."
Mahlkonig Guatemala for FP/drip, Elektra T1 + Mazzer Major for espresso
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EricC
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Post subject:
Posted: Jun 17, 2009 - 09:18 AM
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Joined: Feb 06, 2004
Posts: 584
Location: Liverpool
Status: Offline
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Carl wrote:
Hi dsc, Another (probably daft) thought: What is the size of the flow restricting nozzle (gicleur) on the Elektra? It almost looks as if it might be missing (!) given the speed with which the water seems to gush out.
Hi Tom,
WOW !! After watching the videos, you posted I am thinking along the same lines as Carl, I know this is an absolutely stupid question, but are you sure you replaced the gicleur after the rebuild?
Have you measured the flow rate from the grouphead?
From Home-Barista here :
http://www.home-barista.com/espresso-machines/flow-rate-of-rotary-pump-espresso-machine-t1451.html
"QUOTE "Water debit" -- the first 10 second's flow from the group, including the boiling, bubbling water, should be between 60 to 90 mL, with 75 mL optimal. But this includes all the restrictions in the flow (gicleurs, etc), and is based on not destroying the puck with too much or choking the shot with too little flow.
END QUOTE"
I have never seen water come out of a group head with that much force or speed before. !!!!!!!!!! The actual pull you show in the third video only lasts about 17 seconds.
Good luck with finding the problem.
All the Best
Eric |
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La Marzocco GS/3, Versalab M3, Elektra Nino, Quest M3 Roaster.
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