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Thread: Channelling around edges?

  1. #1
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    Channelling around edges?

    I'm trying to see if I can improve my pour and I think I'm getting some channelling around the edges - getting a naked PF to help see things better, plus to have the ability to use deeper baskets etc.

    Pours start out nice and slow but always seems to run faster sooner than I would like and I think blondes too early. Grinding finer just results in choking the machine, so I think the issue isn't grind size, but more to do with distribution or tamping.

    Around the edges always seems to be some pin-holes and/or large divets.

    I'm using a Jetblack PreciseFit Tamper which fits relatively well, but there is still some play - going to measure with calipers once I get some batteries. Basket is a La Marzocco I believe, but there are no markings to confirm (machine bought second hand). Definitely not the standard Rancilio basket though.

    Currently I'm tapping the side of the portafilter with my palm to distribute and then tapping down on the bench twice to settle before tamping. I'm going to try dosing into a small cup first to try and break up clumps before tipping into the PF.

    Any tips/suggestions will be appreciated!


    Portafilter.jpg

    https://photos.app.goo.gl/lj2w2k9e3BRNpoZo2

  2. #2
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    Certainly looks like it from the photo.

    But if I may, what is the divot in the middle and the faint ring where it looks like it was depressed on the outside?

    Could it be that the coffee is up against the screen and then the puck swells causing pressure on the middle (the divot) and the ring on the edge where the shower presses against it? That could in turn lead to an uneven extraction and channeling around the edges?
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  3. #3
    Senior Member level3ninja's Avatar
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    That centre divot looks like the hex head of the shower screen screw. I'd be interested to know if that divot appears before pulling a shot, i.e. dose and tank, insert the portafilter but pull it out again before running the shot. If that divot still appears I'd suggest lowering the dose until it doesn't and fining up the grind to compensate. Your description of slow at first and then too fast too quickly sounds like overdosing and undergrinding. What is the weight of the beans you are dosing?

  4. #4
    Senior Member Yelta's Avatar
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    I think the divot is the impression of the screw/cap screw holding the screen in place, the flattened area around the edge looks like the impression of the rim of the shower screen.


    Also looks to me like over dosing, makes a big mess and you will finish up with this.




    How old are the beans your using (when were they roasted) who roasted them, what type of grinder.

    Everything you say indicates stale beans too me.

    Suggest buying some freshly roasted beans and try again.
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  5. #5
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    The divot in the middle is the hex head from the Rancilio Silvia shower screen. I've seen the info on changing this out for a button head, but also seen lots of reports that it isn't as big a deal as made out to be.
    The faint ring around the outside is the shower screen edge.

    I'm dosing 20g in the basket, but I will check to see if there is an impression prior to pulling the shot. I used to fill the basket to a mound, distribute and then level off before tamping which resulted in a 22g dose (only discovered once getting some scales to actually weigh my dose!) and that certainly left a divot prior to extracting - for some reason I haven't checked since lowering the dose to 20g.

    Possibly I should be aiming for 18g in the basket with a tighter grind as suggested, so I will try that next.

    Thanks!

  6. #6
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    Quote Originally Posted by Yelta View Post
    How old are the beans your using (when were they roasted) who roasted them, what type of grinder.
    Everything you say indicates stale beans too me.
    Suggest buying some freshly roasted beans and try again.
    I buy beans from the local cafe - they use Axil beans.
    Beans are delivered weekly to the cafe and they then bag them for individual sale.

    Batch I've got at the moment was roasted on 1st Nov, but possibly my storage methods aren't the greatest. The bags the cafe use are Axil 250g bags with a snap-lock top, but they don't heat-seal the top, so possibly air is deteriorating them faster.

    I'll buy a fresh batch and also try dosing less.

  7. #7
    Senior Member Yelta's Avatar
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    Yep, the screw impression is no big deal.

    20 grams sounds well over dosed to me.

    Aaaaaand! the most important questions once again, how old are the beans and who roasted them, what are you grinding with.

  8. #8
    Senior Member Yelta's Avatar
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    Quote Originally Posted by dbun View Post
    I buy beans from the local cafe - they use Axil beans.
    Beans are delivered weekly to the cafe and they then bag them for individual sale.

    Batch I've got at the moment was roasted on 1st Nov, but possibly my storage methods aren't the greatest. The bags the cafe use are Axil 250g bags with a snap-lock top, but they don't heat-seal the top, so possibly air is deteriorating them faster.

    I'll buy a fresh batch and also try dosing less.
    Still reckon it's stale beans, do you have a specialty roaster close by you can buy from?

  9. #9
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    Roasted on 1 Nov even with a little air ingress they are still probably okay - maybe not the best. However Yelta has a point with the grinder, can you get fine enough to pour a 30ml shot in 30 seconds?

  10. #10
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    Grinder is a Macap M2M

    I can certainly grind fine enough to get 30ml in 30seconds, or even longer if I go too far - a click or two further will choke the machine.

    I'll have to look to see if there are any speciality roasters nearby, but I often will get beans bagged the day they come into the cafe (which is within days of their roast date) and they get beautifully rich pours in comparison to mine - of course a Rancilio Silvia vs a La Marzocco Linea isn't a fair comparison , but I've seen some nice pours online!

    There is another cafe in the area that carries Five Senses coffee, so I might pop in there and see if they sell beans and what roast dates they have.

    I'll start with dosing less and grinding finer as the general consensus seems to be that 20g is overdosed, so that's my first mistake to rectify.

    Thanks a lot to everyone for the help
    Last edited by dbun; 1 Week Ago at 01:34 PM.

  11. #11
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    Not to disagree with the wealth of knowledge Yelta has, but your beans seem (on paper at least) like they should be fine and two weeks since roast is acceptable.

    See if you can dose maybe 16-18g in the same basket and grind finer to get a 30ml shot in 30 sec with the lower dose. I think the heart of the problem lies with the swelling of the puck and the pressure you get against your shower screen.
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  12. #12
    Senior Member simonsk8r's Avatar
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    Quote Originally Posted by level3ninja View Post
    That centre divot looks like the hex head of the shower screen screw. I'd be interested to know if that divot appears before pulling a shot, i.e. dose and tank, insert the portafilter but pull it out again before running the shot. If that divot still appears I'd suggest lowering the dose until it doesn't and fining up the grind to compensate. Your description of slow at first and then too fast too quickly sounds like overdosing and undergrinding. What is the weight of the beans you are dosing?
    +1 to this and others thoughts on it
    Yeah that looks like far too deep a hole to be left in the spent puck.. And yeah amount of coffee in the basket is definitely basket dependent. It's not that 20g of coffee is considered overdosing, but 20g for YOUR basket is overdosing.

    Quote Originally Posted by dbun View Post
    The divot in the middle is the hex head from the Rancilio Silvia shower screen. I've seen the info on changing this out for a button head, but also seen lots of reports that it isn't as big a deal as made out to be.
    The faint ring around the outside is the shower screen edge.

    I'm dosing 20g in the basket, but I will check to see if there is an impression prior to pulling the shot. I used to fill the basket to a mound, distribute and then level off before tamping which resulted in a 22g dose (only discovered once getting some scales to actually weigh my dose!) and that certainly left a divot prior to extracting - for some reason I haven't checked since lowering the dose to 20g.

    Possibly I should be aiming for 18g in the basket with a tighter grind as suggested, so I will try that next.

    Thanks!
    Yeah I reckon that'll help a lot lowering the dose and finer grind. And also just to check when locking in the portafilter properly then removing straight away, if the puck is disturbed in any way it's too high a dose. Keen to see how ya go

  13. #13
    Senior Member Rocky's Avatar
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    I have been struggling with channeling for years and never managed to eliminate it on my Diadema Perfetta.
    Usually one or two round the edge of the basket.
    I have tried just about everything mentioned above but the channels persist.
    I wonder if it is caused by excess pressure at the shower screen that is trying to push the water through the puck more quickly than is possible.
    The coffee is still good and occasionally great but it annoys me that it happens.

  14. #14
    Mal Dimal's Avatar
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    G'day Rocky...

    When was the last time you had the machine in for service and requested a "Scace" test and adjustment?
    If everything regarding your grind, dose, distribution and tamp is Ok then it could be down to a machine adjustment.

    Mal.

  15. #15
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    Thanks again to everyone for their help!

    Tried an 18g dose this morning - locked the PF in and removed it to inspect before pulling the shot. There was the ever so slight hint that the puck had touched the hex head bolt. No indent, but just a small section where you could see the grinds had moved slightly.

    The pour was much more stable though and held together longer than before.

    Reading online it seems 16-18g is the sweet spot, so I might play around in that range to see if I can improve things better.

    I pulled a couple of shots this morning and just stuck to the 18g dose and varied the grind to get it pouring ~36g in 25-30s. Maybe I'll dose down slightly until there is no hint of contact with the hex head bolt prior to extraction.

    I think the puck is much better than before. There are two small holes on the right hand side near the lug, but overall I think it is an improvement.

    IMG_2112.JPG

    https://photos.app.goo.gl/ifFSKGcVvlQcQtr92
    Dimal, simonsk8r, LeroyC and 1 others like this.

  16. #16
    Senior Member Rocky's Avatar
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    Quote Originally Posted by Dimal View Post
    G'day Rocky...

    When was the last time you had the machine in for service and requested a "Scace" test and adjustment?
    If everything regarding your grind, dose, distribution and tamp is Ok then it could be down to a machine adjustment.
    Mal.
    In the past there was nobody who serviced Home Espresso machines up here in the sticks. I tried a few local electricians years ago and nobody was doing it.
    Makes me wonder who services the commercial machines in the local cafes. Has to be someone doing this. I will ask at my favourite cafes.
    I have had temperature problems with the Diadema throughout my ownership and have played around with the Thermostat setting including replacement, but seems to be a machine that heats up excessively.
    I address this by putting about half a tank of water through it in cooling flush before I pull a shot. It is very dose sensitive and a lighter dose is always required.
    I regularly stop the pour, tamp the channels with a spoon, and resume the pour. This works surprisingly well. It's just annoying.

  17. #17
    Mal Dimal's Avatar
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    Hi again Rocky...

    You could try CSer "sprezzatura" as I believe he does a lot of commercial work along the central coast.
    If not, he may know of someone who does...

    Mal.

  18. #18
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    Quote Originally Posted by Rocky View Post
    I have had temperature problems with the Diadema throughout my ownership and have played around with the Thermostat setting including replacement, but seems to be a machine that heats up excessively.
    The thermostat in the Perfetta is incredibly sensitive. Even the smallest adjustment you can possibly make will result in a 3-5C change in the upper/lower cut-off.

    I recently completed one and adjusted the thermostat to come on at 95-97C resulting in a cut-off of 108-110C. This yielded a reasonably stable group temperature with less of a cooling flush needed.
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  19. #19
    Senior Member Rocky's Avatar
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    Behmor Brazen - $249 - Free Freight
    Thanks Mal, noted!

    Noidle - that's interesting to hear. I went through a period of trying to adjust the thermostat by tiny increments without much success.
    It would always be either too hot or too cool - I couldn't get the sweet spot. Eventually I replaced the thermostat just to be sure it was not faulty.
    It's not a big drama as I can manipulate the water temp via the cooling flushes, and even the channeling doesn't reduce the shot quality to a standard that would be unacceptable to me - it's just a messy process.
    My next machine will be a more sophisticated model with accurate temperature control.

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