Temperature stability while siphon brewing
Compared to manual pourover brewing—which was my go-to brew method for roughly 20 years—tabletop siphon brewing is more work. It takes more prep time to bring the equipment to temperature before brewing. Afterwards, it takes more time and attention to clean the equipment.
So why bother?
For me, the additional effort involved with siphon brewing is more than offset by improved brewing temperature stability. According to the SCAA’s Coffee Brewing Handbook: “Second to grind, temperature has the greatest influence on the brew’s taste attributes.” The author, Ted Lingle, also notes that: “As a general rule, the temperature should remain constant throughout the brewing cycle.”
The chart above details slurry temperatures measured over a representative siphon brewing cycle using a fast-reading, high-accuracy kitchen thermocouple. Prior to adding the grounds, the water temperature had stabilized at 199°. While the water temperature drops once the grounds are added, the slurry temperature only varies slightly across the brewing cycle, and stays within the optimal brewing temperature range the entire time. The chart ends at the point that I turned off the butane burner to initiate drawdown.
In this particular case, I was using a 3-cup Kono siphon with a brew volume of 350 ml and a coffee dose of 21.5 g. While this brewer may have slight better temperature stability as compared to a larger volume siphon brewer, the temperature measurements are generally consistent with those I have taken while brewing with a Cona Model C, which has a brew volume of 750 ml.
With some practice and attention to detail, it is far easier for me to control my brewing temperature—and maintain it within a very tight temperature range—while brewing with a siphon as compared to a pourover brewer. In fact, when siphon brewing, the slurry temperature is so stable and predictable that I can target different brewing temperatures within the optimal brewing temperature range, depending on the coffee and its roast profile, and easily verify whether or not I achieve these targets.
If you happen to have a copy of Scott Rao’s Everything But Espresso on your bookshelf, pull it down. Now check out Figure 13 (p. 34) and Figure 14 (p. 36) and compare these to the figure above. If you don’t own the book, Seth Mills discusses these figures on his coffee blog, and also does some follow up testing.
Obviously, the best baristas are able to overcome the temperature stability issues inherent with manual pourover brewing methods. However, vacuum brewing can be inherently temperature stable.