Extraction pressure is one of the unknown variables on La Pavoni. Of course, with a La Pavoni, creating a perfect espresso doesn't rely on this measurement. Experience (as I explain in this article) is decisive in mastering this machine. You have to be very rigorous in your protocol. But then if this is not essential, why buy a kit to measure the piston pressure of a La Pavoni?
Quite simply because I am a good geek, I find that everything that is useless is essential. More seriously, since I have owned my machine, I have been wondering how much I of my coffee I extract and finally, I find that this pressure gauge gives more character to my machine, making it more beautiful and more professional.
Presentation of the kit
I opted for the Bplus Cafe kit. The kit can be purchased from Bplus Cafe ($228) and Coffee Addicts ($320).
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| The kit from Bplus Cafe. It is very complete. |
This kit consists of the following elements:
- a modified brass piston and rod
- seals for the piston
- the piston attachment bolts (replacing the original pin)
- a pressure gauge and threaded extension-adapter
- a replacement lever for your La Pavoni machine (the original lever cannot be used because the holes are threaded on the new one for the connection to the piston rod.)
- food grade grease in sufficient quantity for the installation as well as your future maintenance
- Loctite 243 thread glue to hold the rod to the piston
- a pin and the fixing set
Let's go into detail about each element.
The lever
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The new lever is really good quality. It is larger, more robust, the elements are screwed and not held by a rivet like on the original lever of the La Pavoni. The comparison of the two levers is made later in the article, during the assembly of the latter.
The piston
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The replacement piston is made of brass. It comes already assembled (and that's not a bad thing because the piston seals are relatively difficult to install). The difference with the original piston is in its center. The new piston as well as the piston rod are drilled in order to be able to measure the pressure with the pressure gauge which will be installed on top of the piston rod.
The pressure gauge
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Here is the pressure gauge provided in the kit. Graduated in bars, it allows measurement of up to 16 bars. |
The pressure gauge is simple; it goes from 0 to 16 bars and although at first glance it seems large, in truth it goes very well with the design of the La Pavoni once installed. Knowing that espressos are generally extracted with a maximum of 9 bars, we have a very large measurement range with this pressure gauge.
Fixing elements
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In the rest of the kit we find various screws and nuts allowing the elements to be fixed together. Special thread glue and food grade grease are also provided in sufficient quantity for the installation of the kit and for future maintenance.
Installing the kit
Installing the kit is not complicated. Here is how I did it:
The tools needed to install the kit
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You need three wrenches as tools: one 9mm, one 10mm and one 14mm. You can use flat/pipe/ratchet wrenches for sizes 9 and 10 mm but you must have a 14mm flat wrench.
The installation
Piston installation
To install the kit, I started by detaching the lever and unscrewing the top of the piston (using a 14mm wrench) to free it from its chamber. To remove the piston, you simply have to press on its rod and when it falls, the filter screen comes with it. This is followed by the installation of the new piston which is made easier by detaching the head from the machine with the 10mm wrench (see photo below).
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The head of the machine can be removed with a 10mm wrench. |
Before inserting the new piston into the machine head, I greased the piston and the rod with the grease provided in the kit. As I show in the images below, the seals which accompany the piston butt up against the piston cylinder blocking its insertion. To remedy this problem, I pressed all around the joint. This collapses the seal without damaging it and allows the piston to easily enter its chamber. For this operation, I used a butter knife.
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After inserting the piston, I reinstalled the head on the machine and attached the new lever using the supplied pin.
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Installing the pressure gauge
Once the installation of the new piston was complete, I prepared the pressure gauge and then connected it to the piston. Preparing the pressure gauge begins by sealing the thread. To achieve this, there are two possibilities:
- Do what I did and wrap the thread of the pressure gauge with Teflon tape before screwing it to its extension.
- Or use the blue thread glue that is provided in the kit by applying it to the thread of the pressure gauge then screwing it to its extension.
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Pressure gauge with extension installed. For sealing, I used Teflon tape but you can use the blue tread glue provided in the kit by the manufacturer. |
To connect the pressure gauge to the piston, the same sealing procedure must be applied to the piston rod threads. However, first, you must insert the nut (see image below) on the rod. This nut serves as a stop when lowering the lever. Only then did I carry out the procedure to seal the thread. I screwed in the pressure gauge with its extension-adapter. I managed to do it by hand but you can use a 14mm wrench to help. You have to screw in the pressure gauge and its extension all the way because only afterward will you adjust the elements. This adjustment is made by placing the holes on the right and left sides of the piston rod facing the lever mounting holes. To achieve this, I used the 14mm wrench.
Insert the nut before adding the Teflon tape.
Place several layers of Teflon tape on the threads.
Completely uncover the opening from the Teflon tape.
Screw in the pressure gauge using the 14mm wrench.
Adjust to have the holes opposite the opening to secure the lever.
As soon as the holes are aligned with the indentations on the piston rod, I attached the lever to the piston rod. First, you must insert the screws into the washers then, by lifting the lever so as to properly align with the indentations, screw in the two screws using a 9mm wrench.
There you have it, you have finished installing the kit to measure the extraction pressure of your espressos.
The machine with the kit installed :).
How the kit works
To see the kit work, nothing beats a short video.
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| Video of Group Pressure Gauge - Youtube |
Conclusion
As I said in my introduction, this kit is not essential to correctly use your La Pavoni. That being said, I find this kit very interesting because it allows you to see at how many bars you pre-infuse and extract. This adds a certain control over parameters that I did not have control over. So, I was able to discover that I usually do my pre-infusion at around 4 bars and my extraction at around 7 bars.
As for the aesthetic side, this kit makes the machine a little bigger, giving it a more professional look. In short, I don't regret having installed this kit on my machine at all. Plus I find it prettier.
October 26, 2020
By Thomas Garcia
Source: coffeegeek.co/kit-de-mesure-de-la-pression-du-piston-dune-la-pavoni . Translation by Google.
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