I've noticed that on different shirts, there's at least 2 types of ink. For example, Go Japan! has both. The black is a softer, fadable ink while the other colors are a thick ink.
I bring this up for two reasons, 1) to see if this is true and inquire the actual difference in the inks, and 2) to put forth my opinion that the softer ink is better. While I find that a mix is okay, on shirts with large prints the thick ink seems to warp the shirt and make it feel a bit too heavy. Sally Finds a Stray is one example of where the light ink does wonders, while Calling Home's design feels too heavy with the thick ink.