Cordura is nylon that has had air blown through it during the spinning process, so it should work. Rit also had a warning that fabrics that have a water repellent will not accept the dye, so that could be a problem with the bag. Also, from personal experience, true black is hard to achieve. I have an old Cannondale seat bag in dark blue and I like the color. I wish I had a matching handlebar bag.