chengchuan and the OP,

How do the bottomless pour look with and without the fix? When you get the dark ring, do the outer holes take much longer to flow or maybe even stay dry throughout the pull? What's your preinfusion time and extraction pressure like? A video clip comparing the before and after would be super informative if they look different. I do think there is a tendency to under-extract around the edge but feel there are other factors involved as well. Not sure what they are.

K7 wrote:chengchuan and the OP,

How do the bottomless pour look with and without the fix? When you get the dark ring, do the outer holes take much longer to flow or maybe even stay dry throughout the pull? What's your preinfusion time and extraction pressure like? A video clip comparing the before and after would be super informative if they look different. I do think there is a tendency to under-extract around the edge but feel there are other factors involved as well. Not sure what they are.

I've mentioned it previously, but without the fix, I have immediate filling all across the bottomless, very uniform, it flows everywhere.

With the fix, I have a fair amount of doughnuting, edges fill first, which is logical, they have to deal with more liquid.

I've done most of the shots that can be pulled on a robot, I've mentioned them in the OP. Lately, lungos with 5-10s of PF.

I encourage you to try the bottom filter if you haven't yet.

Ken5 wrote: chengchuan, I am assuming that your pick is not from your robot? Doesn't have to be for the info that you provided, but looking at your pucks it does not have the shape of your robot's basket.

It's probably just parallax and a wide-angle lens.

Sorry I missed it earlier. Your comments make sense to me. I will give the paper filter a shot!

Ken5 wrote:Checked my pick this morning and there is a slight dark ring as in your first photo, but breaking it up shows it does not go in much at all. I am not sure how you get your pucks out so cleanly since I do the same as what you have explained. Grounds stuck much the way k7's does, the sides of the puck are not smooth and there are cracks from pulling the air up through the basket when lifting the levers.

chengchuan, I am assuming that your pick is not from your robot? Doesn't have to be for the info that you provided, but looking at your pucks it does not have the shape of your robot's basket.

That is 100% from robot's basket, looks no angle maybe because camera angle problem.

Usually, dark ring ground stuck at bottom just like most people, sometimes got whole puck and I'll take photo to record. But put a paper filter at bottom always get whole puck.

This side photo can know dark ring is start form taper of basket.

How slowly does everyone pull air through the puck when raising the arms after a shot? I really can't seem puck analysis holding much water with the Robot.

I just press the piston all the way down, expel all the water, let everything drip through and pressure equalize while I drink my coffee and when I come back I can lift the arm and the puck remains intact. ¯\_(ツ)_/¯

You don't even have to wait that long.

Wow Roy, must be the angle as I don't see the taper at all. Even your last photos, the puck comes out so perfectly! I have never seen that with mine.

The gasket creates a seal and when you raise the arms air is pulled back through the puck... That's why Paul has said puck analysis is not very useful. Just because it looks to remain intact, air inevitably was pulled through the puck in reverse when the arms are raised, somewhere, somehow, since air cannot enter from the gasket side.

Ok, so I got myself a nicely intact puck also by just letting it sit for a while. Thanks for the tip!
This one shows a bit of dark area at 2 o'clock. While not a whole ring like others shared here, I'm guessing it's due to the same cause. Like I said, I do find the outer area are more prone to slower flow and this is one of those cases, I think. Taste didn't reveal obvious channeling (probably because it's minor) but it suggests there's room for improvement.


I also tried the paper filter method with the included Robot paper. It did show the outer edge flowing earlier (overall faster flow also as expected)...perhaps too fast because the filter was too large to lie flat and had to be folded a bit. Do you trim the paper disk a bit to fit better?

K7 wrote:Ok, so I got myself a nicely intact puck also by just letting it sit for a while. Thanks for the tip!
This one shows a bit of dark area at 2 o'clock. While not a whole ring like others shared here, I'm guessing it's due to the same cause. Like I said, I do find the outer area are more prone to slower flow and this is one of those cases, I think. Taste didn't reveal obvious channeling (probably because it's minor) but it suggests there's room for improvement.
image

It's nice that yours only show minor signs of under extraction. Do you think there's anything you might be doing in particular to help edge flow in your normal shots?

Also, I don't think shots without a bottom paper are channeling, you're dialing your shots so that the center area is extracted to your desired extraction already, so they won't be over-extracted.

I also tried the paper filter method with the included Robot paper. It did show the outer edge flowing earlier (overall faster flow also as expected)...perhaps too fast because the filter was too large to lie flat and had to be folded a bit. Do you trim the paper disk a bit to fit better?

I don't trim the paper, the aim is to encourage flow in areas beneath which there are no holes. Since the edge holes have to account for more flow, it's normal that they bead first.

More importantly, how does it taste?

YeetSkeeterson wrote:The gasket creates a seal and when you raise the arms air is pulled back through the puck... That's why Paul has said puck analysis is not very useful. Just because it looks to remain intact, air inevitably was pulled through the puck in reverse when the arms are raised, somewhere, somehow, since air cannot enter from the gasket side.

If you push all the water out, there's already air between the grinds in the puck, and therefore more air can flow through the puck without disturbing it.