It really is true that not all blacks are the same. Artists who paint usually don't buy black tubes of paint because the black in the tube was created by mixing a bunch of colors together, colors that the artist may not have on her palette already. So artists create their own black by mixing their own colors on their palette together until a beautiful black emerges.
Rug hookers face a real dilemma when it comes to black. Last year when I was hooking the black background around Saint Nicholas, it looked awful. It was the wrong black. I resolved the problem by taking the black wool and overdyeing it with the dyes I had used on the wool for the rest of the santa. It worked! When I hooked it in, it was perfect.
Our eyes are that keen. The color of black matters. So now all my black wool is hand processed with the same dyes I use in creating my palette wools. The picture shows it all. The bottom is the black wool I started with. The top is the rich antique black that came out of my dye pot!