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  • Heston
    replied
    Originally posted by artman View Post
    Good result! Sounds like your yahava beans may not have been so fresh?... Fiori are now in the swan valley if you want extra variety.

    cheers
    Thanks! Yes I don’t mind Fiori either.
    The roast date on the Yahava beans were fresh but I suspect they’ve spent some time in the sun, or at a temperature where they’ve perished.

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  • artman
    replied
    Good result! Sounds like your yahava beans may not have been so fresh?... Fiori are now in the swan valley if you want extra variety.

    cheers

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  • Heston
    replied
    Conclusion:

    I’ve spent some time developing my prep techniques to avoid this channelling issue with improving but wavering results. I found that some bags of beans were more prone than others, all from the same roaster (Yahava Coffee Swan Valley WA). Then I heard someone else having issues with Yahava beans producing wafer thin crema believing their quality has dropped. Change roaster, channelling gone. I now use Bolt Coffee Hazelmere WA and have consistently had no channelling, the extraction is a lot better and the end product much more delicious.

    I believe switching to the more accurate Mazzer grinder highlighted the flaw in the beans, where the sunbeam with a more inconsistent grind hid the issue.

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  • TampIt
    replied
    Originally posted by Rocky View Post
    Sat and Sun I tried one notch coarser on the grinder and there was no channeling on the pours.
    Single and double baskets always pour differently of course, but the double was a little fast on what was a fairly hard tamp, so next time I will tamp even harder and see if I can slow the flow a little.
    I guess I am now into that tricky territory where too hard a tamp builds up water pressure, perhaps predisposing it to channel, and too light produces a tendency to flow too quick with consequent poor extraction.
    The quality of both shots were good so I might be within a whisker of the right combination. Who'd have an automatic machine!
    G'day Rocky

    I would suggest that you try putting about 3 to 4mm of coffee in the basket and carefully tamp it "hard and level" first (old trick I learnt way back). Then complete the rest of your dose as normal. If no channeling, grind it one notch finer (i.e. your original setting) and do the initial tamp more gently. Hopefully still no channeling. Compare the shots and adjust away from there to your tastebuds content.

    TampIt
    PS: semi auto - I would, Fully auto - no way!

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  • Rocky
    replied
    Sat and Sun I tried one notch coarser on the grinder and there was no channeling on the pours.
    Single and double baskets always pour differently of course, but the double was a little fast on what was a fairly hard tamp, so next time I will tamp even harder and see if I can slow the flow a little.
    I guess I am now into that tricky territory where too hard a tamp builds up water pressure, perhaps predisposing it to channel, and too light produces a tendency to flow too quick with consequent poor extraction.
    The quality of both shots were good so I might be within a whisker of the right combination. Who'd have an automatic machine!

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  • MrJack
    replied
    Originally posted by Rocky View Post
    Mr Jack - yes I agree it would stand to reason that the channel is a region on the puck that provides less resistance - but I can see no reason why there would be less resistance at a particular point (I am pretty anal about the dose/tamp process, tapping the porta-filter whilst loading and stirring the dose with a needle before tamping to break up any lumps (I've never seen any lumps))
    Consequently I have tended to wonder about the possibility of higher pressure in the form of steam from the group.
    So, unless there is a sudden increase in temperature near the shower screen, steam could not increase the pressure (which is limited by the OPV).

    Steam could in theory flash boil (due to pressure falling and lowering the boiling point) and maybe disturb the puck, but not because it's at a higher pressure. Seems highly unlikely though, given the pressure and temperature.

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  • Melbroaster
    replied
    Heston, as a next step would suggest making sure your grind distribution is doing the job. If you are interested there are youtube videos that provide a decent overview of techniques like WDT which are imho too slow to do all the time, but useful to be aware of if you arent already to deploy occasionally as part of overall troubleshooting.

    Also re your Mazzer, it will help your distribution if you dose the grinds into the basket continually as you grind rather than waiting until the whole portion is ground.

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  • Rocky
    replied
    Thanks for the suggestions guys.
    Mal - I think you are right about the "something simple" - the machine is very sensitive to minor changes in temp, grind, dose & tamp and I think I have to experiment a bit to see whether it is one of these that has changed. As you say it shouldn't be a little shot of steam as I give it a big flush prior to pour.

    As a last resort I will try a different basket and maybe replace the screen.

    (Heston - sorry to butt-in to your thread - intention was to let you know you weren't Robinson Crusoe, not to take it over)

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  • kyeba
    replied
    Have you replaced your shower screen lately? When I picked up a Silvia a while ago, the shower screen seemed to be due for replacement because every time I used the naked group handle it would show one half of the basket extracting before the other.

    I tried all kinds of things like tamping un evenly in the opposite direction and moving the basket around clock wise. Got a new shower screen and boom fixed it straight away.

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  • Dimal
    replied
    G'day again mate...

    Have you tried changing to a different basket of similar type, eg a Double Ridgeless for another Double Ridgeless?
    Got to be something simple mate. Maybe something has changed slightly in your technique that you haven't noticed...

    Doubt that it's a jet of Steam (or water for that matter) so you just have to try changing one thing at a time, so that you are certain in your own mind just what is going on...

    Mal.

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  • Rocky
    replied
    Hi Mal, my impression is that the channel is usually at the same "clock" position on the basket (in this case about 8 o'clock)
    I have already tried a slightly coarser grind and a lighter tamp and am going to go a notch coarser still.

    Mr Jack - yes I agree it would stand to reason that the channel is a region on the puck that provides less resistance - but I can see no reason why there would be less resistance at a particular point (I am pretty anal about the dose/tamp process, tapping the porta-filter whilst loading and stirring the dose with a needle before tamping to break up any lumps (I've never seen any lumps))
    Consequently I have tended to wonder about the possibility of higher pressure in the form of steam from the group.
    Water seems to come out of the shower screen freely and evenly, suggesting that there is no restriction at the screen.

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  • SniffCoffee
    replied
    My quick fix for channelling is to do a nutating tamp before the final tamp - there's a thread somewhere around about it

    Sniff

    Edit:

    Here's the thread I was talking about:

    http://coffeesnobs.com.au/general-co...technique.html
    Last edited by SniffCoffee; 10 November 2015, 09:18 PM. Reason: added thread link

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  • MrJack
    replied
    Originally posted by Rocky View Post
    All of a sudden I have begun to have minor channeling problems myself.
    Is it correct to believe that channeling is all about the pressure of the water at the showerscreen/puck interface - and therefore the key variables are one or a combination of grind too fine, dose too big and/or tamp too tight?
    In my case, the channel always seems to be in the same spot in the basket which suggests a pressure-point. My machine has always tended to build up too much heat requiring long cooling flushes and I wonder if there is maybe a bit of steam pressure in the group that causes a channel to form.
    I don't believe so. Pressure is the result of restriction to flow from the pump/lever - not the other way around (as almost every espresso related article I've come across would have you believe).
    The culprit is a region within the puck which provides less resistance to flow.

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  • Heston
    replied
    Originally posted by Melbroaster View Post
    Sounds to me like maybe distribution related. One thing you might try is getting both grinders adjusted so the shots you produce are blocked and slightly dripping about the same rate based on the same grind weight, purging as you need to.Then back off the grind a bit to coarsen it on both grinders just a bit, ie 1 notch on each, and purge again as needed so the grind output reflects the new grind size. Then using scales, grind a specific grind weight via the sunbeam that is appropriate to your filter basket into a small cup, shake the cup to break up any clumps, dose into the basket, distribute and pull your shot. Try the exact same steps, including dosing and distributing in the same way with the mazzer. Describe each of the shots via this thread
    Sunbeam: extraction slightly quick, stream slightly thick but central from basket, light sprays, taste slightly bitter
    Mazzer: extraction time not as quick as sunbeam but slightly quicker than ideal, stream ideal, sprays a little more than sunbeam, also slightly bitter but other flavours much more bold

    Both prepared the same way. same volume shaken in container, poured directly into basket (tapped basket half way), dressed with flat dosing tool. I never used the dosing tool with the sunbeam in the past. Wondering if this could be a contributor. Four shots is enough for today, will try the same without the dosing tool tomorrow. And slightly finer grind.

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  • Dimal
    replied
    G'day Rocky....

    Does the channel move when you rotate the filter-basket, or always at the same 'clock' position?

    Mal.

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