A naked / bottomless portafilter is ultimately a great training tool. The naked portafilter allows you to see the bottom of the portafilter basket and observe the espresso extraction. Any issues like channelling, dead spots, or uneven extraction will be easily seen. This presents an opportunity to refine tamping techniques, dosing, and grind settings with a view to improving extraction. See the blog links below for more information and tips about using naked portafilters.
Related blog posts:
Naked and Dangerous: The Bottomless Portafilter
Espresso pour with naked portafilter and a ROK espresso maker
