And ahhh dem Slayers... Beautiful machines...
Had coffee at a new local joint recently that was rocking a 'Slayer 3 Group'.
The coffee was really good and on the way out I had a few words with the Barista as I hadn't seen one of these machines in action previously.
I was intrigued with the big Groups which I assumed was some sort of 'pre-infusion' device.
The Barista attempted to explain how it worked and it seemed to be about being able to vary the flow-rate to avoid the channeling that is so much of a nuisance on my own small machine.
On the Diadema Perfetta, I actually interrupt the pour, remove the portafilter, plug the channel, refit the portafilter and resume the pour. This in addition to stopping the pour for several seconds shortly after starting it in order to allow the puck to be completely soaked before the 'pour-proper'.
And ahhh dem Slayers... Beautiful machines...
On any machine with a 3 way solenoid you will detonate the coffee puck.....
How about some flow restrictor to reduce flow slightly in your Diadema ?
Simon - I simply stop the pour, remove the portafilter, run a spoon firmly around the surface of the puck to fill the channel, and lock it back in and resume. Takes me about 15 seconds.
My "infusion trick" at the beginning of the pour goes like this. Start pour and allow to run for 4 secs. Shut off for about 5 secs. Resume. Seems to help prevent channeling.
Melbroaster - I'm pleased to say this has not happened in my case.
Matt - I was a bit doubtful about messing around with a flow-restrictor when I was ignorant of the issues involved. I live a very long way from Capital cities and anyone that works on Espresso machines.
The following reference suggests to me that it is a complex matter.
Ah that's fascinating, makes sense to stop the extraction and see what you can do to help it before the pour just continues on! Have never heard of that method, if anyone else has any input into that would love to hear from you.
And I'm sure this has been covered elsewhere, but does the infusion trick essentially give a little bit of water in order for the puck to swell and expand, thus potentially filling in any air pockets before full extraction? Like a bloom sorta thing.. Just a guess.. (will move these to new threads if needed)
I'm with Melbroaster...if there is any pressure built up prior to stopping the flow, any 'channeling' you saw was created from stopping the pour. Imagine for a moment, when you are brewing, the inside of portafilter is full of 9 bar pressure. The moment you switch the 3-way valve/small lever, all the 9 bar depressurizes to 0 bar in an instant. The abrupt change in water flow direction & the magnitude of pressure drop will have destroyed the puck integrity.
It's a different story if you had stopped the pour at 0 bar (but you shouldn't see any hole/channel then). It's better to try pausing the lever in mid position for a couple seconds so the puck is preinfused/wet without the pump engaging. Then push to the final up position to engage the pump for actual brewing.
Here's one of the transparent basket videos of what happens when you switch the 3 way valve. https://www.youtube.com/watch?v=-Xmq8NqdUiM
p/s: added a video link after Javaphile's comment.
Last edited by samuellaw178; 24th July 2017 at 10:42 AM.
The puck doesn't swell when it gets saturated with water. Have a look at this thread for some myth busting info.
Java "Mythbusters 'R Us" phile
Toys! I must have new toys!!!
Samuel, the channeling wasn't created by stopping the pour.
The channeling was there first, the 'fixes' only came later in response.
I can tell whether a particular pour is channeling by the colour of the stream at the particular point in the pour that it occurs. If it's not channeling I don't stop the pour to check.
When I stop mid-pour there is no damage to the puck, other than the channel that I stopped it to repair.
I'm thinking that at the beginning of the pour the pressure is relatively low for some time - maybe up to 10 seconds - so my "pre-infusion trick" occurs at maybe only 3-5 bar. Just a thought.
Good point about only opening the lever a bit to wet the puck. That had occurred to me but I haven't tried it yet. Thanks for the links - very informative.
The coffee that I'm producing is generally as good as the best local cafes, but less so when there is obvious channeling.
Very interesting Rocky. It is certainly something new - I've never encountered/heard this channeling-fixing approach but I guess you don't know what you don't know. If I have an E61 or a pump machine I would love to try that.
Thanks Guys, and I would note that I am not trying to 'promote' any of my bizzare Barista behaviours as "the solution" to any particular problem.
Where coffee is concerned, I'm a "searcher" - constantly trying to understand what is happening and what might solve any minor problems.
A basic machine like my Diadema is a good place to start as it has a few quirks that I have had to try to come to grips with in order to get the quality I demand.
One day I will buy something more upmarket (with a PID!!!) and a better grinder than the Rocky, but for the time being I still enjoy playing with the Perfetta.