I recently bought a bag of Handsome Espresso roasted on 12/26. Before that I was using some fresh Counter Culture La Forza. I got a naked PF for Christmas, so I've been watching my pulls and trying to improve my technique. The La Forza was pulling perfectly (good timing, nice tiger-striping, good, centered cone, etc.), but the Handsome is clearly channeling in the interior of the basket somewhere with some very messy, laser-like spurts and a very quick, gushy pull (15s or less). Any thoughts?

I'm using the same technique for both coffees. I've tried going finer on the grind (Vario), though I haven't gone to the finest settings yet, since I'm reasonably happy to drink imperfect shots rather than putting stuff down the drain in the morning until it's perfect. The Handsome shots are still 90-100% crema on the initial pull, so I'm happy that the beans are reasonably fresh. Blind basket pressure is 9.5 bar, and I'm brewing at 203F (according to my Silvano's pressure gauge and PID controller).

My messy counter and I would appreciate any advice.

Some coffees are just finicky that way and require that your grounds distribution is perfect. Have you tried WDT?

bbarth wrote: laser-like spurts and a very quick, gushy pull (15s or less)

I think that's where the problem lies. If my grind was too coarse, that same spritzers tend to happen under my bottomless portafilter. Try grinding it finer.

Another thing is, if you're updosing previously with very little headspace to the showerscreen, you might want to try lower the dose a little. Some coffee(or rather darker roast) has more volume with the same weight. This could cause channeling too.

Here's an update:

1. Much, much finer seems to be the solution. I was able to stop the spurting and get a more consistent (but still a little short) pull two clicks from the finest setting on the Vario. Previous coffees have run much closer to the middle of the range on the micro (left-side) slider based on how I haven't it tuned currently (based on manufacturer's instructions).

2. The Handsome Espresso seems to bloom/grow a lot more than past coffees. Experiments with both normal and underdosing seemed to get a shower screen impression on them even though there was no impression at lock-in. That's, perhaps, a lesson for the future. The finer ground stuff did not seem to show this problem as much.

Thanks for the advice, y'all. It's clear I'll have to be more aggressive with my changes in the future when things go wrong!

You don't mention dose weight. Dose is a combination of fineness and weight. Sometimes the grind remains the same and the dose varies, sometimes the grind changes and the dose remains the same and sometimes both require adjustment.

Ian: Do you think that the weight has a big influence on channeling? That seems to be my problem with this coffee. I can fine tune once the coffee stops exploding all over the place.

The comment about extensive blooming is a give-away to at least part of the channeling problem. Coffees still gassing heavily provide significant pressures inside the puck that can cause cracks and channels. Give Handsome a little more time to de-gas, and its behavior will almost certainly improve.

Anvan: You think? It was roasted on 12/26 and bought on 12/31. It seems like most folks around here are done with their beans 15 days post roast.

bbarth wrote:Ian: Do you think that the weight has a big influence on channeling? That seems to be my problem with this coffee. I can fine tune once the coffee stops exploding all over the place.

Yes.

Coffee density varies. A dense coffee that produces fewer fines is not going to perform the same as a less dense one that produces more fines. If the less dense coffee is held in place by the shower screen, the more dense will have too low a volume to contact the screen, changing puck compression.

IMO, there is far too much emphasis here on using a fixed XXg dose and arbitrarily adjusting the grind when a slight mass adjustment yields better results.

ALSO IMO, at least on e61s, there is a no man's land of medium doses where consistency is very difficult to achieve. With these doses, the coffee initially expands to the screen and all is well until sufficient coffee is washed into the cup. At this point the the screen ceases to exert as much pressure on the puck and the flow goes pear shaped*. AGAIN, IMO, convex tamper make this shot even more difficult as the center of the puck is thinner.

* http://en.wikipedia.org/wiki/Pear-shaped

Regarding the dose, you mention that it's high enough to press against the dispersion screen. I suspect that a thick puck magnifies gas-induced channeling since the CO2 has more resistance before escaping from the filter bottom. I readily admit we're into "thought experiment" territory here, but, for example, the gas in a very thin puck would find its path of least - and much lower - resistance to be downward and through the filter basket holes instead of pressing sideways and breaking up the puck.