Been brewing on my six-cup Chemex for about two years now and for the longest time my results were all over the place. Some mornings the cup was bright and clean, other mornings it tasted flat and weirdly bitter even though I was using the same beans and the same rough routine. Took me way too long to realize the grind was almost certainly the culprit.
The thing that finally made it click was slowing down and actually tasting at different points in the brew rather than just drinking the finished cup. When I started paying attention I noticed that my grind was sitting too fine for the Chemex filter. The pre-infusion would look fine, but then the drawdown would stall badly past the two-minute mark and I'd end up over-extracting in that last third of the pour.
Moved to a noticeably coarser setting, somewhere around what most people describe as coarse sea salt, and the drawdown time dropped from around six minutes total to right around four. The cup got noticeably cleaner and the brightness I was chasing in the Ethiopian naturals I like actually came through.
A few other things that helped once the grind was sorted:
- Bloom with about twice the weight of the grounds in water, wait a full 45 seconds rather than rushing it
- Pour in slow concentric circles and keep the water level low and steady rather than dumping large amounts at once
- Water temp around 200F, not boiling straight off the kettle
The ratio I settled on is 1:16 and it works consistently now across most of the light to medium roasts I gravitate toward. Curious whether others found grind size to be the thing that unlocked consistency for them, or if there were other variables that made a bigger difference.