I like to keep swatches of all my inks in a binder. In the past I've used Rhodia 80gsm but paper never felt right; too flimsy and I was never good at cutting accurate and consistent rectangles. In the past there was Maruman Mnemosyne Word Cards (which I never used), this year (2017) there is the new Col-o-ring cards, Robert Oster has some swatch cards as well and I have also found some good card stock myself. I'll be comparing these 4 different card stocks with Rhodia 80gsm and Tomoe River (as baselines). They all often perform quite differently and bring different attributes to the table! This is a very image heavy comparison with over 135 images!