We worked together with Czech barista trainer Diana Dolejsi, and World Barista Champion, Gwilym Davies to design and conduct a series of experiments to help us gain a better understanding of best practice when it comes to syphon brewing.
In this video, Diana and Gwilym demonstrate the syphon recipe they found the most reliable after conducting the series of tests. They also walk you through the 5 separate objectives of the syphon experiment. Read on for an in-depth summary of each test.
1. Does brew water get hotter or colder when it’s held in the upper chamber?
In this experiment we take a look at what happens to the brew water temperature if you leave the water to dwell in the upper chamber for longer. Does it gradually cool down? Or do the warm air currents rising up from the lower chamber cause the water to gradually heat up? Does this situation change if you use a less powerful heater — i.e. a flame vs an induction hob?
When you add the coffee to the water in the upper chamber of the syphon, the temperature initially drops by 2–3°C. What happens next depends on your approach: Left unmanaged, after about 30 seconds the temperature will usually climb back to the starting temperature before the grinds were added. Then, the temperature will continue to increase until the water in the bottom chamber reduces to below a certain level. After this, the temperature will drop slightly — this occurred after around 4 to 5 minutes. (See Syphon 6 results, below.)
Eventually, the water in the bottom chamber will completely evaporate and the temperature in the upper chamber will decline more rapidly, until the water draws down from the upper chamber back to the bottom chamber. After the syphon was removed from the heat source, the drawdown generally occurred after the temperature of the coffee slurry dropped to around 91–92°C.
Note: Allowing the bottom chamber of a syphon to completely dry out can be dangerous as the class can shatter.