Is black, strong, flexible not really black? All of the models I received are of a bluish, purplish hue. look here
If I remember right from some class, art or maybe some class about printers. Black and white dyes and paints and what have you are hard to make, as few things on earth are true black or white to be able to extract the pigment from. So usually black is dark blue or purple. But I'll ask Nancy to be sure.
The black dye does indeed have a dark blue hue to it, but we have worked out a way to let the dye soak in long enough for that effect to be really minimal. The pieces that I've received look black even when put against a true black background. It sounds like this could potentially be a defective print. How many prints have you received? Do you have any pictures? Preferably one against a pure white or pure black background. (pure blacks show the contrast better, but it's harder to photograph)
I received 4 separate prints and they were all a bit blue. Here are some photos. The camera and thumb screw are black. http://www.thomashuang.net/products/nps75/nps75.html