Puck screen and commercial lever group

#1: Post by **LObin** » July 18th, 2021, 11:31 am

The Flair58 puck screen doesn't agree with my Londinium 1. At all.

Unless I grind very fine and pull 30+ seconds shots, I get the same weird behavior every time. As soon as I pull the lever down, I get watery drips in my cup. It lasts for a few seconds and then it stops as if the shot wants to resume normally. That's all happening during preinfusion (at boiler pressure 1.4 bar). When I release the lever, the remaining of the extraction seems adequate. Coffee puck looks textbook perfect.

If I remove the puck screen and pull another shot, keeping the other variables the same, I get a great extraction.

I leave the puck screen inside the portafilter in between shots so it's hot. I've tried tamping with it, without it, EPHQ14, EPHQ21, IMS 18-20, made sure there's enough head space... nothing will do. Recently made the switch to 64mm SSP MP burrs... same behavior.

I don't need the puck screen but I do like the cleaner group and believe it can provide extra forgiveness, especially since my wife pulls her own shots.

What gives???
Anyone else with a commercial 58mm lever is using a Flair58 or Bplus puck screen?

#2: Post by **Mad Scientist** » July 18th, 2021, 2:04 pm

I think no matter how well the screen is pre-heated it's still going to take away some brew water temperature for itself. Our Londinium L1 legacies have no adjustable temperature control to compensate for the use of these screens.

There is a whole discussion on this screen on the Levercraft Ultra Basecamp. It just doesn't look good for our machines imo.

As an aside note, we are advised to pull a short 50ml flush after each shot to ensure the thermosiphon has not vapor locked, and so I do that and wipe the group screen. It's clean.

MS

July 18th, 2021, 11:43 pm

Thanks for your answer but the issue is not temperature related. Nor taste related. It's simply a weird behavior during preinfusion that doesn't seem to happen with the Flair58 or other 58mm machines.

I've had my L1 for 4 years now. I know about thermosyphon stalls

#4: Post by **pizzaman383** » July 19th, 2021, 8:26 am

what dispersion screen do you use on your L1?

July 19th, 2021, 9:03 am

Londinium IMS 35um

July 19th, 2021, 10:15 am

There must be some flow effect due to interaction between the two.

Have you tried any other puck screens or paper filters? If not, you could try that to see if the same thing happens.

July 19th, 2021, 10:59 am

I've been thinking it could be caused by a close but not perfect fit inside the basket. The Flair58 puck screen is 58.5mm. The baskets I've tried seem to leave a tiny gap around the puck screen (.1 -.2mm).

Maybe when the piston is raised and the water hits the puck with a certain level of "violence", the path with less resistance is not through the puck screen but rather on the sides. Once the top of the puck is filled with water and pressurized, the behavior lessens. That would explain why it only happens for a few seconds...

It could also explain why it doesn't seem to happen with other machines like E61 and Decent (water enters the group more gently) as well as Flair58 (no pressure other than gravity when lever is raised)

I guess I could try a paper filter to see if it behaves any differently. The only other puck screen that I know of is the coffee-sensor one. It's also 58.5mm but 0.2mm vs 0.5mm for the Flair58.

Since it was more experimental than a real necessity, I'm close to give it away to a friend with an E61 machine.

I was just curious as why it won't work in my machine but seems to work quite well for most users.

It works wonderfully on my LPE pre-millenium (SS mesh Aeropress filter)...

#8: Post by **truemagellen** » July 19th, 2021, 12:45 pm

Try lowering the lever a bit slower to that the group fills a bit slower instead of rushing in and possibly finding path of least resistance around the edge of the screen and under it

I find with the Elektra the bplus screen works amazingly well but it is a very vigorous release of water and so I have to be extra mindful of a slow lever to ease the water flow volume into the group otherwise it disturbs the screen and I find coffee on the top of it and side of basket. It also shortens the coffee bed which means I can't get as large of a dose on a strietman basket but that is another matter

another option however it seems unlikely is remove the londinium shower screen so that the flare screen is the only line of defense, perhaps that will help if there is some sort of weird airpocket backpressure forming that messes up the puck since the water flow is being limited by 3 elements, shower, flare screen, and coffee bed (think 2 expansion valves on an HVACs causing trouble)

September 1st, 2021, 6:06 pm

I wanted to report back ìn case other members run into the same issue.

I ended up ordering the 58.5mm Coffee-Sensor puck screen from bluestarcoffee.eu

It works as expected on my Londinium. Not sure if it improves the extraction yet but it sure keeps the group super clean, which is the main reason why I wanted a puck screen in the first place

It's much much thinner than the Flair58/Bplus puck screen and has very different hole patterns. I'm suspecting the Flair58 doesn't work well with the "violent" preinfusion of my Londinium (or other commercial levers probably). The weird "leaks" I was getting when water would hit the screen and puck are not happening with the thinner Coffee-Sensor puck screen.

It's obviously not a necessity but I dig it.

September 1st, 2021, 6:27 pm

These things look interesting - but something confuses me - what is meant by the group getting dirty? Is this like grounds on the dispersion screen, like in a pump machine with a three-way valve? Or?