Puck sticks to dispersion screen. Is this due to channeling?

Postby Ian_G on Sat Jul 02, 2011 12:55 pm

The problem: Almost everytime I make a coffee the contents of the basket end up stuck to the dispersion screen above the portafilter. When I remove these contents back into the portafilter it consists of a round puck that is almost the same diameter as the basket at the top and a rounded out version of the same underneath. In other words almost the entire contents of the basket end up sticking to the dispersion screen. The contents are saturated, although what remains in the basket seems drier.

I have had the Elektra semiauto for about 8 weeks now and although this happened early on, it was a rare occurrence. Now, as I say, it's every time.

I always dose to 14 grams, so I know it's not overdosing that's causing it. Whether I use the WDT or not, it still occurs. If I remember and remove the portafilter as soon as the shot is poured then I can usually catch it before it sticks. What often happens in this instance is that the "3/4 puck" is lying at an angle as a complete block as if water has penetrated around the circumference, got underneath, and floated it free - if that makes sense.

On the rare occasions I manage to remove the portafilter before anything has happened, there is a faint fracture line all around the circumference, about 2 mm in from the edge of the basket.

I should also add that I take great care to ensure the grounds are level in the basket. I'm still using the plastic tamp provided with the machine, but this does not reach all the way to the edge of the basket. Nevertheless as this problem did n't happen before with any regularity, I am doubtful that this is the cause.

So is it channeling, or something else that's causing the problem?

One final point is it does not seem to affect the taste at all. It's just such a pain to clean up afterward.
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Postby another_jim on Sat Jul 02, 2011 2:08 pm

I do not think it's related to channeling. Instead, it's a gotcha in the way the double dispersion block design used in the Elektra, Bezzera and Brasilia groups. There is very little space in the water channels, so the suction when the three way exhausts the pressure is fierce. This can suck up the puck like a vacuum cleaner.

Image

Blipping the pump before removing the PF to knock the puck back into the basket is a good habit.

It helps to remove the shower screen and lower dispersion block once every week or two and clean them. If three or four of the ten little holes get blocked, the problem gets worse. You'll need a stiff wire, like those used to clean the steam nozzles to clear any gunk.

It also helps to change the cleaning schedule, more frequent chemical backflushes using less detergent and fewer pump cycles -- compared to an E61 group, there is a lot less space, so it requires less detergent, but that space clogs faster, requiring more frequent cleaning.

I heard some people reamed and widened the ten holes in the lower dispersion block a little. However, there was no report whether this worked or not.
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Postby howard seth on Sat Jul 02, 2011 3:16 pm

I have been getting the sticking puck sometimes too on my Elektra Semiautomatica. However, it is infrequent - and some days not at all. Generally, if it happens - it is the first espresso of the morning. The sticking puck phenomenon seems too be a recent occurrence over the last couple months - hardly ever happened the first 3 years I owned machine: no idea why it is occurring more lately.
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Postby cafeIKE on Sat Jul 02, 2011 5:31 pm

Ian_G wrote: always dose to 14 grams...

Mistake #1 : Dose for BEST TASTE
Mistake #2 : Worrying about compost

Surefire method to prevent sticking is to grind much coarser.
Optionally dose higher.
Taste be damned :P
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Postby homac on Sun Jul 03, 2011 1:19 am

I agree with this comment.

I have had pucks stick to the group head on my Quick Mill Alexia. I set my grind a wee bit coarser and increased the dose. Finding I am dosing around 18-19g for a double.

In addition to resolving the sticky puck issue I found the taste of the shots much more appealing (for me anyway).

cafeIKE wrote:Mistake #1 : Dose for BEST TASTE
Mistake #2 : Worrying about compost

Surefire method to prevent sticking is to grind much coarser.
Optionally dose higher.
Taste be damned :P
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Postby Ian_G on Sun Jul 03, 2011 7:16 am

another_jim wrote:I do not think it's related to channeling.
It helps to remove the shower screen and lower dispersion block once every week or two and clean them. If three or four of the ten little holes get blocked, the problem gets worse. You'll need a stiff wire, like those used to clean the steam nozzles to clear any gunk.


I removed the screen and dispersion block and gave them a clean. So far so good - thanks for the tip.

cafeIKE wrote:Mistake #1 : Dose for BEST TASTE
Mistake #2 : Worrying about compost

Surefire method to prevent sticking is to grind much coarser.
Optionally dose higher.
Taste be damned :P


I gave your idea a shot, but I prefer the taste of 14g and finer grind. Actually I have found that pretty much every roast I've tried tastes best to me at 14g and as a ristretto. I read somewhere that Italian roasts are designed to use 14g, whereas US roasts taste better at higher doses. Whether this is true or not I don't know. The notion comes from an Italian importer to the US who was trying to justify the increased cost of his products (due to shipping) with the idea that less coffee is needed to produce the espresso, so the costs balance out.
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Postby bowie on Sat Jul 09, 2011 11:56 am

homac wrote:
I have had pucks stick to the group head on my Quick Mill Alexia. I set my grind a wee bit coarser and increased the dose. Finding I am dosing around 18-19g for a double.


Same here on my Vetrano randomly, and I never figured out how to stop it. In my case I had to run the pump with portafilter removed and let the remains glop into the basket.
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Postby howard seth on Sun Jul 24, 2011 5:39 pm

Follow up on puck sticking on the Elektra: in the last couple months had that sticking puck problem - but almost never had it before, with my Semiautomatica, until recently - I had the machine repaired this week - due to a sticky valve above boiler - and also raised the pressure stat up - I had, mistakenly, lowered it considerably too low - brew temp. is about 200 F now. (1.3-1.5 on the pressure gauge). Sticking puck no longer an issue it seems.
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Postby UFGators on Mon Aug 01, 2011 7:51 pm

I would be shocked if you were getting 200f with 1.2 to 1.3 bar pressure stat setting. My t1 is set between .9 to 1.0 and I get 200 to 202 after 8 secs after the "water dance" during cooling flush. Have you measured the temp? I am curious because I am still learning my machine!
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Postby Psyd on Tue Aug 02, 2011 2:58 pm

cafeIKE wrote:Mistake #1 : Dose for BEST TASTE
Mistake #2 : Worrying about compost

Surefire method to prevent sticking is to grind much coarser.
Optionally dose higher.
Taste be damned :P


Note that this is complete sarcasm, and Ian climbing up on his combination cross/soapbox/pulpit. ; >
He is not actually advocating changing the brew technique to remove the puck regardless of the taste of the resulting espresso.

Mistake #1 : Thinking that anyone that has any concerns about the resulting puck is a puckocentric puckologist.

Mistake #2 : Thinking that the puck can't be indicative of dosing, grinding, or maintenance issues because you're just going to throw it away.

While I do agree with Ian that the puck is not important as long as the result in the cup keeps getting better, it *CAN* tell you things about what's happening during the extraction. So can watching the nekkid. While I would never do what Ian is suggesting (albeit sarcastically) and re-arrange my technique just to make it look better during the extraction or have a 'better' puck, I wouldn't ignore signs of dramatic change in either without a corresponding change in my technique. This would mean that something other than what I was contributing was changing in a way that I wan't aware of or controlling (or that perhaps my technique was slipping) and I'm pretty sure that that would show up in the cup, as well. 'Puckology' is less a road-map to great espresso as it is a hint of where you left that trail and in which direction the path lies.
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