Hi,

I bought a new lagom p64 a few months back and ever since then, i have been experiencing this issue where my shots get "runny" towards the end with channeling even with proper rdt, wdt, distribution and tamping. This issue only started since i changed from my breville smart grinder to my lagom p64.

The video shows 2 shots pulled at 0.6 and 0.5 grind size settings, and i am using the omni burr sets from lagom themselves. If i am not wrong, this is the revised version of the burrs which has been improved from the initial version.

Settings:

Lagom P64 Omni
0.6-0.5 grind size
Speed setting = 4

Linea Mini
Brew pressure = 9 bar
Plumbed in
9 seconds preinfusion

P.S. i have tried playing around with different grind size, grind speed, preinfusion time, they always still cause this issue

Both shots were a 1:2 ratio with 18g in and about 36g out



Video of 0.6 grind setting
http://www.vimeo.com/834344158?share=copy

Video of 0.5 grind setting
http://www.vimeo.com/834344513?share=copy

Is your espresso machine able to lower pressure over time to compensate?

OP's profile says his machine is a Linea Mini. My understanding is that these coveted machines do not have flow control, nor "on the fly" adjustable OPVs. Absent those features, physics will take its course; as solids are extracted from the grinds, the resistance will diminish. And the flow will therefore increase.

That said: in looking at the videos, unless they were artificially sped up the grind size is not working. Perhaps don't worry about the number on the dial, but instead grind finer until you get the desired result?

yea there is not flow control except to use pre brew or pre infusion via the la marzocco app, and it only controls the flow during the start of the extraction

My suspicion is the p64 is producing less fines so it doesn't restrict flow like you're used to. Based on the overall flow rate on your video, you need to grind finer. Try going finer than you think you need as a baseline and adjust from there.

I used a stock LMLM for 5 years with a big 98mm flat burr grinder and remember that flow increases a lot near the end of the shot. Channeling was always an issue unless I stir the grinds meticulously and even then, it happens sometimes. Mine was an early model without preinfusion/app. That combined with the higher flow 0.8mm gicleur that's on the LMLM makes it more prone to channeling... is how I rationalized it at least.

I think i will give it a go again, or maybe remove the pre infusion and retune it from there, but i also have a IMS shower basket and a 6 hole diffuser screw instead of the default 4 hole ones, do you think that affects anything much?

I recently added Rick Bond's EMP flow control to my LMLM and had issues with shots running too fast. His response helped me, maybe it's valid for your issue too. I needed to grind a lot finer, a lot finer than logically made sense to me.

"bottom line, if flow rates are too high it must be a function of the grind/dose/coffee not being adequate to impede the water flow. I would suggest getting a control in place like some commercial freshly roasted coffee. In general the principle of controlling pressure during preinfusion will allow you to grind finer to achieve the same parameters of mass over time. "

Too much headspace can also create this symptom.

Unless you're able to adjust the flow during the shot, it will run faster with time. You're dissolving around 20% of the grinds in the basket so there is less to hold back the flow as time goes on. Modern, flat burr sets can have more acceleration that traditional sets, flat or conical.

In my experience with "filter" roasts as espresso, an extended soak is result of having to grind finer to get the balance in the extraction that I prefer. In my experience with medium and darker roasts, extended soak tends to downplay subtle flavors and increase the generic roast flavors.

I don't think that a high-flow shot is a poor shot. High flow during a shot may not be channeling. A messy high-flow shot may look like channeling, but usually aren't. If anything, a basket ground and dosed for higher flow than traditional is less likely to channel than a classic grind and dose. There's a lot of folklore around espresso that has been shown to be folklore. While it may be a useful guide for some, it isn't the only way to get a tasty espresso.

I'm using a lever but new SSP HU red burrs. The shots start good but with a coarser grind they can go fast. They taste good, though, especially light roasts.

The grind adjustment is very slight in a sweet spot. Just a nudge to coarse and the flow is 1:3+ in 30 sec. A nudge to fine and it's 1:2 or less in 30sec. Maybe the burrs need a bit of seasoning. Or some more alignment. The stock burrs didn't settle down for a while but they were cast steel.