Hello everyone! I am new to at-home espresso and am struggling to dial in my first bag of espresso (tend to be on the bitter side). One thing I keep noticing is channeling on the edges of my puck, which may cause certain areas to over-extract, contributing to the bitter taste. I cannot seem to overcome this channeling issue.

My puck prep involves grinding right into a 20g IMS precision portafilter basket, use a WDT tool to distribute (5 needles) and break up clumbs, although I still see small clumps after this step is complete. I then use a Nomcore distribution tool and then a Nomcore tamp. This is a classic case of having all the equipment, with bad execution haha. I imagine this is normal for beginners.

Image 9569 - Less channeling, but still some on the outer edges. This grind size was at the 1 setting on my grinder. 5 seconds to first drip. 31 seconds to 1:2 ratio.

Image 9619 - A lot of channeling it seems on the outer edges. This was with a grind size 1.25 setting (coarser) than image 9569. 5 seconds to first drip. ~24 seconds for a 1:2 ratio.

Any clue on what I can do differently?

If you load the portafilter into the group head, tighten, then remove it, is there a ring in the (dry) grind around the perimeter (like in your photos)? Or is that ring formed when the puck gets pulled up into the shower screen when the pressure is released at the end of the shot?

To add to the prior post, it looks like the ring around the water screen is touching your grinds. In other words, you have too much coffee grounds or aren't tamping hard enough. I would try using 18 grams of coffee and / or tamping harder to create more head space.

If that isn't the issue, remove your shower screen and do some cleaning.

Total guess but I wonder if you're way too fine. Your extraction times are good but that's with the channeling, if it weren't channeling you'd probably get very little output. If you were in the right ballpark I would think channeling would cause you to gush and overshoot your desired output.

Agree the ring impression is interesting though.

The ring did seem odd to me, I'm currently using a 25lb spring loaded tamper and adding 20g to the grinds. I'll do the test today and report back. Thank you!

espressoren wrote:Total guess but I wonder if you're way too fine. Your extraction times are good but that's with the channeling, if it weren't channeling you'd probably get very little output. If you were in the right ballpark I would think channeling would cause you to gush and overshoot your desired output.

Agree the ring impression is interesting though.

I was thinking this as well. The shots are way too bitter. earlier on when I was grinding the beans coarser, there was channeling, but the shot tasted much sweeter. I'm going to try going coarser and report back!

Dtkoffee wrote:To add to the prior post, it looks like the ring around the water screen is touching your grinds. In other words, you have too much coffee grounds or aren't tamping hard enough. I would try using 18 grams of coffee and / or tamping harder to create more head space.

If that isn't the issue, remove your shower screen and do some cleaning.

So I pulled a shot at the 2 grind setting (coarser) based on feedback at 18 grams. The ring still appeared and channeling pursued around the edges. A very messy shot that finished in 10 seconds.

What kind of grinder and espresso machine do you have? A 10 second shot sounds like the grinds are too coarse.

By "messy," if you mean there's water on top of the pick, that's not a big deal. Just means that there was a little extra room at the top of the basket, although that doesn't make it harder to diagnose the puck after pulling a shot.

ZJ wrote: The ring still appeared

When I release pressure at the end of my shots, the puck gets aggressively pulled up against the shower screen approximately 100% of the time. So, the imprint I see doesn't really tell me anything about the how the shot went, as I consider the puck damaged at that point.

I use filter paper inserts at the top and bottom of the puck, largely just to keep everything clean, but if I suspect there is channeling I can usually see the imprint of it on the bottom paper. And whenever I'm in a 'no-channeling' mood, I'll insert a filter paper roughly midway through the puck. I concede that's a huge complication to the workflow and generally isn't necessary, but it can help confirm if channeling is really the problem.