This is what I recommend on natural fabrics!

Made by Tsukineko, Memento Luxe ink is permanent on natural fabrics when heat-set (iron at the appropriate temperature for fabric). Images will remain vibrant on fabric even after repeated washes.

Memento Luxe is a creamy, rich, blendable pigment ink. This inkpad features a vibrant and rich colour that will look great on a project involving paper, fabric, wood, leather and much more.

TSUKINEKO-Momento Luxe Full-Sized Inked Inkpad (7.5cm x 4.5cm)