People who have worked with bocote?

[Sam Fleisher]

The pictures are of the same cane shaft that I turned then a buddy put a twist on by hand. After applying "the real milk paint" Half & Half (tung oil and citrus oil) the black streak showed up after approx. a day.

We're unsure if this going to be permanent or if it will soak back in.

Or even what caused it. Assuming it's because the wood is oily. But not sure.