Our custom fabric masks are printed using dye-sublimation (aka dye-sub), which is a common way of printing on various fabrics. It works like this: Your design is digitally printed in reverse on heat-transfer paper; once printed, both the paper and the polyester fabric are fed into a heat-transfer machine that acts like a large iron, transferring the image from the paper directly to your face mask's fabric. The dye-sub process actually dyes the design into the fabric, resulting in a durable, high-quality mask that can be easily cleaned.