Coffee — My Journey to the Dark Side of the Roast, part 5

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PID'ing Silvia

One of the few real problems with the Silvia is its stock "brew" thermostat. This thermostat is set at 100°C or 110°C. Originally, it was 110, but there were complaints that the brewing water was too hot. The 100° thermostat was the "solution."

Unfortunately, both of these thermostats have a basic flaw -- which was probably the source of the "too hot" problem, where the Silvia would blow steam out the portafilter's spout. They have a dead zone of about plus or minus 10 to 15°C -- they heat 10-15° above the midpoint before the heater kicks out, and they cool 10-15° below midpoint before starting to heat again.

This is an issue because you can taste a difference of 1.5-2° in the brewing temperature. Many people try to solve this by "temperature surfing." They run water through the steam wand until the heater kicks on, turn off the water and wait about 25 seconds before starting the water pump. This enables them to be at approximately the same boiler temperature for their espresso pulls. The key word is "approximately," as this just isn't close enough.

The engineering approach to solving this problem is to add a PID, a Proportional/Integral/Derivative process temperature controller to maintain the temperature of water in the Silvia's boiler. I used Murph's Silvia PID Page as my basic guide for my PID addition. I added some enhancements, which I discuss on my Espresso page.

The Hottop Roaster

In June, 2003, I purchased my Hottop coffee roaster through a retailer based in California. The Hottop had been "beta-tested" in the US since late 2002 and I was patiently waiting. Well, let's just say I was waiting.

Finally, it was released as a finished product. I discuss my Hottop joys and experiences on my Hottop Roaster page. The Hottop is now more widely available, including from my favorite coffee supplier Sweet Maria's. I added a variac (variable transformer), digital voltmeter and digital thermometer to my Hottop setup to reduce variability in my roasts

I finally sold my Hottop in December 2004, after changing to an RK Drum in a gas grill (read on...)

The Vacuum Pot

I had read numerous articles, emails and messages about brewing coffee in a vacuum pot before I ever bought mine. Of course, I was dreaming of the $150 Cona models. I knew that I wouldn't ever buy one of those. The Bodum Santos looked like a cheap version, has a plastic filter disk, and has a reputation of being somewhat fragile. At a list price of $80 this was unreasonable.

One day, Amazon.com offered a short-term special price on the Bodum Santos. I bought one. I use it in the evenings about once a week for decaf. Sometimes, it even gets used on the weekends for my "regular" homeroasted coffee.

Coffee brewed in the Santos is very fresh and clean tasting. This really brings out the sweetness in a light City or City+ roast of a good coffee bean (see my coffee roasting pages). If I wasn't careful, I got a fast cooling and resultant fast filtering of the coffee. This was bad in that I also got a lot of coffee fines past the filter disk.

After reading about Cona glass filter rods and their use in various other brands of vacuum pots, I bought one through eBay for about $7 including shipping. The Cona rod made a huge difference in the resultant coffee. The filtration was much slower and much more complete. The coffee was beautiful in the vacuum pot and in the cup. I highly recommend using a Cona glass rod in a Bodum Santos. One caveat, though, you need to put a large ceramic or glass bead or something like that into the pot to act as a bubble initiator. By trying to heat water in a smooth glass decanter, you can actually heat it above the boiling point. When a bubble finally forms, it can shoot the water and coffee all over the room AND YOU!

the journey, part 1 |  2 |  3 |  4 |  5 |  6 |  Posters

Copyright © 2002-2006 Terry A. Stockdale