Vacuum brewers were originally designed to pull water through much finer ground coffee by using the force of vacuum in the final phase of the brewing process.
It was believed those days that finer ground coffee produced a tastier cup. It must be noted that finely ground coffee increases flow restriction and thus requires additional aid to achieve the optimal brew time and extraction efficacy. Coarsely ground coffee will work too, but you won’t be getting the most out of your siphon. The occurrence of washout kinetics works best with coffee that’s ground in the finer spectrum. Washout Kinetics – the technical term for what pressurized water does as it passes through and around coffee- forces more insoluble material off the coffee particles and ends up in the cup. In the situation where the classic cloth filter is used (the one you get when you purchase a siphon), it will allow a portion of the oils into the bottom chamber and prevent fine particles from going through.
What you get is the positive attributes of the oils in the coffee – heightened body and aroma level, without the negative inputs of the bean fiber- the possibility to over-extract, reduce clarity, and negatively affect mouthfeel.
Note- the oils in coffee have a similar fatty acid profile to that of butter and cottonseed oil. As you can imagine, this undoubtedly contributes to the textural quality of your brew.
Cotton filters are the best but need to be kept incredibly clean. Superfine metal mesh filters are good too (much easier to clean) but microscopic fines still find their way into the bottom chamber (over-extracting and creating astringency in the cup). This is visually noticeable. I don’t believe the metal filter does justice to Siphon brewing, although – the metal filter housing is able to hold an Aeropress filter. Paper filtered Siphons can be super interesting, especially with acidic coffees – Central and East African washed coffees come to mind.
If you’re interested in experimenting with a stainless steel filter for your Siphon- check out Cape Coffee Beans
Tips and tricks
- Using high heat initially will potentiate vapor pressure build up and seems to allow for a more powerful vacuum in the draw- down phase. Creating a higher contrast in temperature around the bottom chamber will have will help with the draw-down too. A weak vapor pressure buildup where lower heat is used may cause issues with the vacuum intended for the last phase of the brew- and in this way can directly affect extraction.
- If you’re using the classic cloth filter- it’s best to clean this as soon as you can after brewing. Take out the siphon top chamber after brewing, flip it upside down and unlatch the filter and take it out. Hold the filter face down as you run water through the filter until its clean. After this give it a soak in boiled water for 5 min. Do it again if necessary. Cleanliness with these filters will ensure that you’re tasting the coffee and not the filter.
- Water temperature manipulation can be done more efficiently by using a gas burner and adjusting it once the water has fully risen to the top. Using the paddle to wave the water around can assist in a temperature drop if too hot.
- Extraction can be optimized in the lower temperature spectrum by using turbulence intentionally. The more you agitate the coffee grounds, the quicker they will extract, but beware of too much agitation. You can agitate the grounds in the brewing chamber by using the included paddle. Be sure that you’re coffee is all extracting evenly, regardless of the situation.
Until next time
Buy your Siphon from Origin De Waterkant or Maboneng