Creating Teflon Gasket for Pre-Millennium La Pavoni

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drgary
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#1: Post by drgary »

Hello:

While using my pre-Millennium La Pavoni equipped with a group thermometer and manometer, I realized that I could measure temperature accurately to pull consistent shots but was still facing the need to cool the group between shots. I decided to try a Teflon gasket, an idea of our member LVX and done for me by DJR, just like I've installed on my Elektra Microcasa a Leva, which makes that machine so stable I can leave it on all day, walk up and pull a dialed in shot.

With the dual switch Pavoni I still need to toggle switches but after adding a Teflon gasket the temperature swings much less because the group is more isolated as a heat sink. Here's how I did it.

First I used a brush to apply a thin coat of chocolate syrup to the group surface on the boiler. Then I pressed a 5 by 8 paper card to that to make a stencil. Here you see the stencil just above the group opening.



I used a compass circle cutter to create the circle in the center of the template.



I cut the outline of the template with scissors and pinned it through the Teflon sheet onto a wooden board.



Then I cut the outline with a hobby knife, which wasn't hard to do.



I scored the Teflon using the same circle cutter. Since Teflon is more resistant than paper and the circle cutter can bend inwards and start to cut a spiral, I carefully held both ends while moving the Teflon against the cutter and vice versa. In other words, I took care to make an accurate circle despite the flimsiness of the circle cutter.



To finish the circle I carefully applied the hobby knife at the center of the blade, angled as you see here.



Then I used a 7mm leather punch backed by a cutting board. I used pliers to avoid crushing knuckles if I missed with the rubber mallet. The pin holes acted as centering guides for those holes. There's an opening on one side of the leather punch where you can see through to the cutting stock underneath. This worked easily on the first blow. If the holes aren't quite centered where you need them you can repunch them as the gasket will still seal.



Here's how the gasket fits to the group:



I slathered the gasket with Dow 111 and fastened it firmly on the group. It works fine. I found I needed 1/16 Teflon sheet for adequate insulation, twice the thickness used on my Elektra MCAL.

This morning I pulled three excellent shots on this machine, taking the manometer up to .85 bar at most before toggling off. With the group pre-heated I can have as little as .5 on the manometer. In that case I'll do one or more extra half pumps to create sufficient pressure while watching group temperature on the thermometer. To ensure sufficient preinfusion I wait for drips to start appearing at the bottom of the cup, preferably evenly dispersed.

If I heat the machine all the way using the High switch for steaming, the group will still exceed shot-pulling temperature and will need to be cooled, but I was pulling straight shots and not overheating enough to create an interruption.

Added: Although I did not take the time to do rigorous testing before and after, the temperature swing when only pulling shots using the Teflon gasket seems to be less than half of what it had been. Perhaps it is possible to isolate the group even more with additional layers of gasket. I hesitate to do that too much because I don't want to overstress the two screws that are holding the group to the boiler.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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RayJohns

#2: Post by RayJohns »

Not a bad little gasket there :) You are becoming quite the fabricator these days.

Ray

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drgary
Team HB

#3: Post by drgary »

Thanks, Ray. I appreciate the compliment coming from you. I'm enjoying rolling up my sleeves and finding ways to make these mods work.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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bostonbuzz

#4: Post by bostonbuzz »

Great work. I am a huge proponent of these gaskets and think that everyone should have one. While they don't totally solve the problem, they make it much more manageable. I saw similar results with my (sold) cremina. The idle temp was nearly perfect and the post-shot temp was lower, and the cool down time was better. Overall, better in every way. That's probably why the new ones come with one!
LMWDP #353

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drgary
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#5: Post by drgary »

bostonbuzz wrote:Great work. I am a huge proponent of these gaskets and think that everyone should have one. While they don't totally solve the problem, they make it much more manageable. I saw similar results with my (sold) cremina. The idle temp was nearly perfect and the post-shot temp was lower, and the cool down time was better. Overall, better in every way. That's probably why the new ones come with one!
That's very interesting! Never knew. I wonder if the plastic sleeve in the Millennium Pavoni group is a similar solution of isolating the brew chamber from the heat transmitted through the machine's case to the group bell?
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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drgary
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#6: Post by drgary »

Today I found that the Teflon gasket also helps cool the machine faster after steaming. I made a capp for breakfast and the group temperature rose to about 15F high for shot-pulling. Five minutes later I returned to find the machine had cooled by 12F. I could have chilled the portafilter, but instead since the pressure had returned to zero I added 1/5 tank of cool, distilled water, then switched on, ground and pulled my next temperature controlled shot. Previously I would have had to let the machine sit for 10 to 12 minutes or would have needed aggressive cooling techniques, but that's not needed anymore since making the group a more isolated heat sink.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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yakster
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#7: Post by yakster »

You are tempting me to try this on my Gaggia Factory.
-Chris

LMWDP # 272

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drgary
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#8: Post by drgary »

Chris:

I'm surprised you need anything beyond dipping the portafilter in water to cool a Millennium machine. What's your PSTAT setting?
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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yakster
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#9: Post by yakster »

I don't really need anything beyond a cool portafilter, I guess it's really not necessary and I shouldn't invent problems just because there's a solution out there.
-Chris

LMWDP # 272

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michaelbenis

#10: Post by michaelbenis »

Love the second part of that sentence! Definitely a quotable quote! :D

Nice work, Gary.
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