I've had a Silvia + Rocky for some time now. It's got a PID and bottomless portafilter. Also trying to use the WDT technique to de-clump the coffee. But results are mixed in terms of channeling. On certain types of coffee it comes out great, but not on others.
A couple of weeks ago, I took apart and cleaned out the Rocky. Then I also replaced the burrs, as I've had the grinder for about 2+ years now.
The coffee is the Epic from 49th parallel and is within the 12-18 day window.
I haven't changed the pressure valve settings, as I doubt the problem is there and I don't have a pressure gauge.
I really like the set-up and sometimes it makes great coffee, but the consistency is just not there.
Here are a couple of videos, with the double and triple basket. Would really appreciate some advice on how to troubleshoot this.
I have not watched the videos (dial up here) but here are some general thoughts:
- check that you are not over dosing. After locking the PF in, remove it and check to see it if the coffee has been disturbed by the shower screen or center screw.
- thoroughly dry the portafilter before dosing coffee.
- a lot more people than you think get channeling. They do not know it because they have spouted portafilters.
- Silvia's water delivery (as with all such machines) is quite dramatic. it rams up very quickly and that helps reveal any weakness in the puck.
- try another style of basket. Maybe one of the straight-sided triple, LM type baskets.
- just for yucks, try this- tamp slowly, increasing force over about a three to five second time period. Let me know how it feels and if it helps. I would find it interesting to compare your findings with mine.
- be sure to be gentle when locking the portafilter into the group.
I'd love to hear some more answers to this, because I've been struggling with channeling issues as well since I got my bottomless portafilter (and before, I'm sure - just without my knowledge).
I did notice your shot was only about 15 seconds (on the double) and 12-18 day old espresso seems a bit old to me. But I'm not sure whether that alone would lead to the channeling issues. I'm definitely interested to hear what others have to say about this because it seems very similar to my technique and my issues.
There was a bit of a screw indent in the puck (which happens to me as well), but I'm not sure how to distribute the grounds evenly without having enough grounds in the portafilter to level it. I try to level with my finger after a straight tool (as you do) to try and downdose a bit. But any less than that and you wouldn't be able to reach the grounds and would have to rely on trying to shake the grounds evenly before tamping or something.
One theory I have with my issues is that the mini-fridge I've got my espresso machine sitting on isn't quite level, because no matter what I do it always seems to come out quicker on the side closest to me. I'll have to get out a level and check that next time I'm at home.
Good luck... and I hope someone who knows a lot more than me posts some useful tips!!
I'm sure that most people using this machine without the bottomless portafilter have channeling issues as well and they just don't know it.
In terms of the indentation on the puck: - for the triple basket, I think it's just from when the coffee expands. Which should be OK - on the double basket, since it's not very deep, I think it will be very difficult to dose less, and not get the shower screen screw to touch the coffee once the portafilter goes into the machine. But the screen itself should not disturb the coffee. I guess one solution to this would be to get a convex tamper.
In terms of the coffee age, I think that 10-18 days is not bad, to let it de-gas after the roasting period.
I usually cut the shots short, once I start to see channeling come through.
One thing that I will try next is to give it a quick flush first, to see if this removes some of the initial pressure.
I watched both videos, and I'd start by saying stop tapping the portafilter! I noticed in your double basket video it looked like you were getting a spray or two from the sidewall area. This could be due to you breaking your side seal when you tap the filter. Those little bits stuck to the walls? They don't matter that much, and if you want to get rid of them, blow them off or something. Tapping the filter, in my experience, only leads to channeling issues and donut extractions (and marring that beautiful chromed brass!). Additionally, I'm in the "10-18 days sounds pretty old" camp. Most conventional wisdom dictates somewhere around 4-5 days for initial rest, with some coffees requiring more, but not generally more than a week. I'm not familiar with 49th's blend, but it strikes me as an awfully long rest. I'm not saying it's a dud by then, but it wouldn't hurt to try some fresher. Finally, as for dosing the double basket: have you tried weighing doses, instead of dosing by volume? You may get better results if you stick to 14-16 grams in the basket, ground fine enough for a ~25 second extraction (or to your taste). Once you've kicked the channeling, then experiment with larger doses. The puck really shouldn't come in contact with the screw before brewing. The screw contact limits water contact, and leads to extraction issues, and possibly channeling due to the puck shifting when contact is made. Many recommend the nickel test, wherein a nickel's width worth of space should be available between the puck surface and the screw, but I've found "not contacting" to suffice.
The no tapping advice sounded interesting, so I tried it today. Also tried to change: - grind less fine - not to move the fork around so much - tamp more carefully and evenly - not to twist the tamper as I press down so not to disturb the coffee - do a quick flush at the beginning - not to overdose
But no luck. The channeling still persists. I know that I have had better results in the past with the same coffee.
I haven't tried the tinfoil hat yet.
It would be nice to be able to swap the grinder, the coffee machine, or the person behind the machine and see which one of those is the culprit.
Hopefully so. I watched the videos and I think that you have to grind finer. The finer the grind the better chance you will have an even stack of particles that will decrease the chance of channeling - conceptually the difference between pouring water over sand vs tennis balls. This difference is accentuated under pressure.
I'd suggest grinder finer to the point when you choke the machine (get very little coffee out or a very long extraction) and then back off from there to find your point. On the rocky there are only 1-2 grind settings that will be ideal. Finding the true zero (where the burrs start to click) may help. I found that a setting of +4-6 from the true was good for me but this is highly variable between grinders. This small window for "perfect" espresso is why many are turning to other grinders nowadays such as a stepless lelit or the Vario.
Dose if very important as well so a scale WILL significantly improve your consistency with making shots I found. Many will stick with dosing by volume but that is only after the grind is dialed in and they are familiar with the bean and roast. With Epic shoot for 14g for a double. 21g for a triple. I found that triples gave the best and most consistent naked pours on the Silvia.
You may be a bit over aggressive with the WDT. I always use a very sharp object not the mini-fork - my go to equipment is a small wooden skewer - paper clip works as well. Don't be overly aggressive or disruptive. IMHO what you are mainly doing is improving the distribution down to the lower reaches of the stack of grinds. Use it ever time if you are going for the perfect naked extraction.
OK, thanks for everyone’s input. I think I have made some progress.
Today, I picked up a new batch of beans, from a 10 day roast. Epic Espresso from Aug 10, 2010. I had a shot from the same beans at the local shop, and it was really good, so the beans should not be the problem – granted my machine will be a lot more sensitive than theirs. I tried both the double and triple baskets. Changes that worked well for the triple: - For some reason I had lowered the temperature by 2C on the PID before when I was trying a different coffee. I brought it back to 109. I may have to play around with this a bit now that the channelling issues have improved. - I was a lot more careful with drying the basket thoroughly - I made sure I leave enough headroom, so that there is no contact the screen or screw. For my own reference, this is around 14 seconds grind at +6 setting on the Rocky. - I was not as aggressive on the WDT. Used a toothpick instead of a fork. Made sure I specially got to the lower corners of the basket. - I was careful with the tamping. Light tamping at first, to get a “level” distribution, then harder tamp. Tamp circling around the edge of the basket lightly first. No knocking on the side of the PF Here is what the loaded basket looked like: http://www.youtube.com/watch?v=6lYh6qyHkGA - If the machine had been idle for a while, gave it a quick flush (1 sec), before inserting the PF And here is the extraction ground at 6+ on the Rocky: http://www.youtube.com/watch?v=PO-BE00OJ7A And a bit tighter ground at 5+: http://www.youtube.com/watch?v=me1YDRAhFSY Compared with the original one at: http://www.youtube.com/watch?v=o3avPtK2r1A
Some interesting things with the double basket: - If I try to make sure the coffee in the basket doesn’t touch the screen, I can’t dose too much. Probably around 8 seconds grinding (sorry, no scale). When I do this, I can’t avoid a lot of channelling. I think the problem is that as the basket is not very deep and has fairly rounded bottom, the tamper bottoms out against the curved edge of the basket, without being able to tamp down on the coffee. Maybe this is place where the original plastic tamper might be useful – will have to try. - So for the double, I have to overdose a bit – and the coffee will inevitably touch the screen, or at least the screw. If I do this, I don’t get as much channelling. Here is the double now: http://www.youtube.com/watch?v=CiiSmU8c95M - Compared with the original double: http://www.youtube.com/watch?v=WpPpZ0hB6B0 Still some work to do, but I see some definite improvements. Now I need to work on the taste. Not quite sure how to describe it, but it’s a bit more bitter than what I get at the coffee shop. Maybe overextracted?
Posted Sat Aug 21, 2010, 6:20am Subject: Re: Rancilio Silvia + Rocky - Channeling issues
Lower the PID temp. Considerably I would imagine. Every machine is different but my PID was set at around 215F (temp probe at the boiler). If you have a good thermometer you could try to measure the water at the group with the styrofoam cup technique. Another data point is that my Vivaldi is currently set at 93C for Epic. Most brewing temps are recommended in the 197-200F range. I'll bet that you are too hot = too bitter
Drop the temp until the shots are sour and then bring up. Will need to wait between temp changes.
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