Controlling and understanding the water pressure in your coffee machine is important in order to successfully extract it. This parameter is completely controlled on automatic machines while it is less on a manual machine such as the La Pavoni. Some knowledge can help to better understand and better control the water pressure when using the La Pavoni machines. In my article, I will especially talk about the pressure exerted on the piston when you press the lever.
Water pressure in the boiler
Some models of the La Pavoni are equipped with a pressure gauge. This allows according to the pressure to estimate the water temperature. The documentation indicates that the boiler pressure must be between 0.6 and 1 bar. The water will be about 94 °c. I explain this much more precisely in the following article.
La Pavoni manometer.
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The manufacturer recommends carrying out the extraction in the green zone of the graduations [0.6-1 bar]. |
| La Pavoni manometer |
Measuring the water pressure in the piston of a La Pavoni
The water pressure in the plunger has an important influence on coffee extraction. I became interested in the subject and found several methods to measure this pressure.
First Method: Convert the force applied to the lever in bar
Some models of the La Pavoni are equipped with a pressure gauge. This allows according to the pressure to estimate the water temperature. The documentation indicates that the boiler pressure must be between 0.6 and 1 bar. The water will be about 94 °c. I explain this much more precisely in the following article.
To know the force applied to the lever of the coffee machine, there is nothing simpler: just put the machine on a scale.
The mathematical formula to use is available here. However, to make reading easier, a user of the home-barista forum posted a chart.
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| Graph for converting the pressure of the lever to water pressure in the piston |
On professional machines, it is recommended to extract the coffee with a pressure of 9 bar. According to the graph, on a La Pavoni, to obtain this optimum pressure, a force of approximately 13.7 Kg should be applied to the lever.
You can do some testing and then estimate if you apply a comparable force on the lever during your checkouts.
Second Method: Install a manometer on the piston
Another (more costly) method is to replace the piston to allow instantaneous measurement using a pressure gauge. If you are interested in this method, you will find user feedback on the Internet. Personally I find the rendering pretty, but at $300, too expensive. The kit can be bought from Coffee Addicts and from Bplus Cafe. See the article on the installation of the kit here.
Third Method: doing a DIY
I discovered by chance a method much more hardcore (but precise and less costly). On the Forum home-barista, a user pierced the group head to attach a manometer on the side. The rendering is a bit weird, but ergonomic (when you press the lever the pressure gauge on the side of the unit is facing the user).
Conclusion
In conclusion, to properly master a coffee extraction with a coffee machine La Pavoni, you must remember the following things:
- The boiler pressure must be between 0.6 and 1 bar.
- Leave the machine on long enough for the machine to be hot (some talk about 20 minutes, but personally I leave it on for less time and I have good results).
- Grind the coffee, pack it…
- Open the steam valve for a few moments to let the false steam escape
- Lift the lever to allow a little water to flow. This step allows you to heat the piston to the right temperature, remove the coffee residue from the previous extraction.
- Place the portafilter (if using a spout filter holder, it must be heated before, as is the cup).
- Lift the lever, do the pre-brewing (I do 6 to 7 seconds of pre-brewing)
- Lowering the lever by applying approximately 13.7 kg of force, extraction must be between 25 and 30 seconds (with pre-brewing)
- Enjoy your coffee :)
Published 17 April 2018
By Thomas Garcia
Source: coffeegeek.co/en/measuring-and-understanding-pressure-on-a-pavoni
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