On Filter Coffee, and Why Most CTOs Are Wrong About It

I am Indonesia’s most opinionated CTO on filter coffee. This is not a competition I entered — it is a conclusion others have reached, and I am not disputing it. Filter coffee is a system with parameters you can control. Grind size, water temperature, pour timing, bloom duration, dose. You set them, you adjust them, you own the outcome. This is why filter coffee is the correct choice. The alternatives do not offer the same terms.

The Case Against the Alternatives

Tubruk is not a coffee preparation method. It is a surrender of control dressed up as tradition. The grounds sit in the glass and keep extracting while you drink. Your first sip and your last sip are different coffees — not because you made two decisions, but because you made one and then stopped paying attention. The extraction continues without you. For someone who wants a consistent, intentional cup, this is disqualifying. The taste argument is secondary. The process argument is sufficient.

Espresso is a different problem. The barrier to doing espresso well is capital. A credible setup starts at Rp 5 juta. Anything worth owning seriously starts at Rp 10-15 juta. A Hario Switch, a decent grinder, filters, and a kettle costs under Rp 1 juta if you are careful. The entry point to filter coffee is attention. The entry point to espresso is a purchasing decision most people make once and then live with. These are not equivalent systems.

The Method

I use a Hario Switch. Not a standard V60. The Switch is an immersion-percolation hybrid — the valve stays closed during bloom, which means the grounds steep in hot water before any drip begins. Extraction starts on your terms, not gravity’s. This is not a preference. It is a more controlled process than an open dripper allows.

The parameters, and the reasoning behind each:

Beans. Light to medium roast, natural process, fruity profile. The roast level determines everything downstream. A darker roast forgives mistakes at every stage. A light roast punishes them. I prefer the terms where precision is rewarded.

Grind. Slightly coarse. The beans are light, the target is clean and fruity, and over-extraction is the primary threat. A coarser grind slows extraction. This is the most important dial in the system.

Grinder. Non-negotiable. The grinder is the first serious purchase in any filter coffee setup. Grind consistency is the variable that preground coffee permanently surrenders. Anyone who claims to care about their cup but uses preground has identified the most important control mechanism and chosen to abandon it. This is a valid choice. It is not a serious one.

Temperature. 80-90°C, never above 92°C. The range is bean and grind dependent. The ceiling is not. Light roast, fruity profile, coarse grind — the entire setup points away from aggressive extraction. 92°C on a light natural process bean is not an experiment. It is a mistake you have already made.

Bloom. 45 seconds, valve closed. The CO2 releases, the grounds saturate evenly, and extraction begins under controlled conditions. Skipping the bloom is skipping the setup. The cup will tell you.

Pours. Three. Not four. The fourth pour extracts bitterness. This has been tested across enough sessions to constitute a finding. Three pours is the conclusion.

Ratio and dose. 1:15 at 20g, producing 300ml. The ratio is standard in specialty filter coffee circles. The dose is not — the common starting point is 15g, which produces 225ml. I like volume. The solution to wanting more coffee is more coffee, not more water. Scaling the dose up and scaling the water up proportionally is not the same as adding water to a smaller brew. One maintains the ratio. The other dilutes it. These are different things.

Filter. Standard white filter. It has one job: let the flow happen at its natural rate. It has no other responsibilities and I have not given it any.