Here is picture of the stick tiles. We discovered that these tiles were covered in the soot-like material on installation day. They got over-looked because the tiles on top of the box were fine. Fortunately there weren't as many of these tiles and I it didn't take long to clean them. But it still made a mess, and wasted more time.

This is what my hand looked like after picking up one tile.

Did Walker Zanger ever apologize or provide explanation?

Yes, eventually I spoke with someone higher-up who not only apologized, but also provided a partial refund. They also offered to provide tile for a future renovation, but I didn't choose to take them up on that offer. That was 3 years ago and the crackle tile has held up beautifully in a very busy kitchen. Behind the sink and range top look as good as when newly installed. I'll never forget having to scrub those tiles, but glad it all worked out in the end. You can read more about the ordeal in the kitchen forum. If you're considering purchasing tiles from Walker Zanger I would still recommend their tiles, and they did come through with a little persistence.

That looks like ink. Did you ever determine what it was?

Had they offered to remake/reship the tile? Our first batch of tile (not WZ) had issues that required scrubbing, but instead of us having to do it, they picked up the shipment and remade/reshipped the entire order in under two weeks.