RDT: Spray or Drop or the Spoon Method Not every grinder has low retention, it’s important to make sure you’re getting out what you put in.
Make sure the puck is absolutely dry. Dosing funnel helps with distribution as well.
Distribution. The objective is to have an homogeneous and even bed of coffee to avoid uneven flow. To remove the clumps, use a needled tool to stir and move around the coffee inside. Go deep, it’s important to reach the base. Go higher slowly until out of the coffee.
Paper in the bottom of the puck? It reduces the oils, increases flow and yields higher extraction. It’s hard to get by those papers, it’s easier to cut actual paper filters. It’s very optional, it yields a different profile.
Puck screens? Thick disks of metal mash that stays on top of the coffee bed. They help distributing the water. It also allegedly prevents the expansion of coffee towards the top. It apparently increases the yield. They’re hard to clean, so it’s a bit of a nuisance.
Tamping. It’s done before the puck screen, but maybe after too. Make sure the pressure is as vertical as possible. Doesn’t have to be infinitely strong, just feel until coffee is not squishy anymore. There are tampers with auto pressure relievers but it’s not that valuable.