Posted on 17 March 2011 by Nate
The next step of our perfect shot walk through for the Rancilio Silvia hinges on getting proper brewing pressure from your machine. In its past, the Rancilio Silvia has had some notoriety for the excessive amounts of pressure it produced. The correct pressure for good espresso extraction should be at around 8.5 to 9 bar of pressure. This creates the ideal environment for flavor extraction from the coffee itself, which when coupled with temperature, sets up a great shot of espresso.
Prior to some modifications made around 2005, the Rancilio Silvia often tested out at pressures of around 11 bar. This obviously forces the water through the puck too forcefully and created havoc with shots and quite a bit of channeling as the espresso was drawn. However, during the modifications in that year, Rancilio incorporated a newly designed pressure regulator which worked wonders. Now the Rancilio Silvia comes out of the box with the more appropriate 8.5 to 9 bar as it continues to today.
There is, however, still some variability in the pressure produced. If you own a newer model Silvia and want to really dial in the pressure which the machine produces, there are some options to do so. The newer models of the Rancilio Silvia come with an adjustable OPV, or pressure valve.
Here are the basic steps for modifying the pressure on the Rancilio Silvia:
- Be sure to shut off the machine and unplug the power cord.
- Take out the plastic water tank and remove the top panel of the machine by loosening the screws.
- Find the pressure regulator, which is a brass colored cylinder with an elbow that leads directly into the boiler. The locknut at the end closest to the plastic tubing is the adjustment mechanism.
- Using a small crescent wrench, you can turn the adjustment mechanism to vary the pressure in the regulator. By tightening the nut, you are increasing the spring pressure and subsequently increasing the pressure. By loosening, you’re going to take tension off of the spring in the regulator and reduce the amount of pressure.
- Be sure to check that you haven’t loosened the adjustment nut too far and created a pressure leak.
- Put the top of the machine back in place, tighten the screws down, and replace the water tank. That’s it!
As you can see, with later model units, there really isn’t much to adjusting the boiler pressure. If you would like to test the pressure, there are calibration units available which lock into place on your group head and give you an indication of brewing pressure. By taking a little time to experiment with the adjustable pressure valve, you’ll sometimes notice big differences in the taste of the espresso you make with your Rancilio Silvia.