Cafec Abaca+ Coffee Filter

“Sharp and bitter = over-extracted. Cardboard could be under-extracted, but I suspect other things happening there. My suggestions/questions: * I would actually start with water temp. Drop that down to 92-93°C to start out. With highly-processed coffees, like co-ferments and funky naturals, you can even go a few degrees lower if you still get bitterness. If water is too hot, you can really pull out those harsh, bitter notes at the tail end. I've found the 92-93°C range ideal for many of my coffees. * You don't mention your kettle at all. Are you using a gooseneck? If not, you really need one to get consistent pours. * You did mention flow rate, so maybe you have a gooseneck kettle. If so, you may be pouring from too high up and agitating your bed too much, which can cause a lot of bitterness. Try pouring from closer to the coffee bed. * You can also try minimizing agitation by doing center pours, rather than circular pours. Slow, gentle, center pours. You can also try doing a spiral/circle pour at first, then center pour after that to get a *little* agitation in the beginning. Another option for super-low agitation is a drip assist tool like the Melodrip. * You didn't menion the filters you're using. If you're using slower filters, you may need to grind way too coarsely to get your current brew times. Try a faster filter, like the Cafec Abaca or T90 rather than the Hario filters. * Your brew times with lighter coffees may be a little on the slow side. I often see brew times in the 2:30 to 3:00 range for light roasts. (I'm not familiar with the Switch recipes, though.) By using faster filters, you might be able to cut this down a bit and avoid having to grind really coarsely to keep brew times down. * Are you rinsing your filters before brewing? Some filters, particularly the unbleached filters, can add off flavors from the paper itself. Rinse with hot water before brewing, and rinse your cup out after dumping the rinse water.”