by Randy Glass - Copyright 2004 - All rights reserved
E-mail me at firstname.lastname@example.org
Silvia Brew-Temperature Control
When making espresso there are a number of variables that should be controlled to as great of an extent as possible. We often discuss controlling the grind and the brew time as well as the tamp procedure and pressure as key factors. Two other key factors are water pressure and water temperature. For most of us there is not a lot we can do about directly controlling pressure, but there are some tricks that can be used for manipulating the brewing temperature even when our machine does not offer a specific control over that variable.
Back in February 1, 2001, Greg Scace posted to Usenet on alt.coffee his findings from experiments he did with his Silvia using a digital thermometer device [entitled "Temperature study of my Sylvia (looong)"]. He used a process to control the temperature (outlined below) and charted his findings. From these we were able to see that the Rancilio Silvia can pull a shot with a temperature stability that was generally heretofore not thought possible from a home machine of such a (relatively) humble price point. Many thanks go to Greg for doing the testing and documentation to show the value of the process.
I document here how I had applied what Greg taught us when I brew espresso. I used this process for every espresso I created up until the time I installed a PID control:
Prepare for the session- Allow machine to come to full operating temperature. I usually try to allow thirty minutes to an hour or so. The PF should be too hot to comfortably touch for more than a second from the heat conducted by the brewhead. Have beans in the grinder, pre-gring for at leat the first pull, cups ready, a steaming pitcher at hand, etc. When you are ready to make some espresso, follow these steps.
THE ACTUAL TEMP SURF PROCESS
1) Place steaming pitcher under hot water tap, open the hot water valve, and turn ON the hot water switch. Pump hot water until the heating lamp comes on (indicating that the brew thermostat has turned the heating element on).
2) The instant the light comes on do the following things as simultaneously as reasonably possible:
3) While the timing continues, grind, dose, tamp, lock and load. Position your glass under the PF, ready for the shot.
4) Have your finger on the brew switch and when your timing shows your predetermined time has elapsed, begin the pull by turning on the Brew switch. Contemporary Silvias (since mid to late 2001 and newer) with the 110c. thermostat seem to like as much as 50 to 60 seconds.
At the end of any session, always leave Silvia with a full boiler so that when the next session begins you can leave her on for an extended period without fear of running the boiler dry. Be sure that the steam valve is completely closed. This is particularly important if you have your machine on a timer.
*1 Be aware that these instructions were written with the Rancilio Silvia in mind. If you machine does not have a separate switch for hot water or the light goes off when the heating element is energized then you will have to adjust these instructions to suit your machine.