I've never tried to stain it on purpose,so I can't help there.
What I CAN tell you from working on a couple Schons that were worked on by someone else before me is that Ivorine IV can certainly be stained by accident or negligence,maybe even a manufacturing defect,to the point it almost can't be fixed.
In both cases I'm referring to,there was enough black stuff down in the pores that there was a 1/8 wide streak the full length of the ferrule.
One of these had the original tip on it,so maybe that one was just a fluke. I managed to improve it some by using a Magic Eraser and clean 220/320/400 and compressed air before facing the ferrule and installing the tip,but even after I finished my process,there were still little black spots that wouldn't come out without taking a .010 cut or sanding aggressively. I just sealed it with CA so it wouldn't get any worse. I showed it to the customer,and he said he could live with it since it was better than before.
The other one had a Kamui Black installed on it,and the staining looked very similar,but no matter what I did,it still looked the same. I showed it to the customer while he was waiting,and explained what could have caused it. He said he knew it had the streak,but he also said he could live with it,so I finished it up,again sealing it with CA so it didn't get worse. Tommy D.