Can I use Photo Black ink on matte papers or use Matte Black ink on glossy/luster/semigloss paper?
Technically, yes you can, but I strongly recommend against doing so. Using PK on matte papers will result in significantly weaker blacks, lower contrast, and lower color saturation. Using MK on glossy, luster, or semigloss papers will usually lead to severe scuffing problems (i.e., the ink does not adhere to the paper surface and easily comes off with rubbing) unless the print is carefully sprayed afterwards. This question is commonly asked by users who wish to avoid the cost and time of switching between the PK and MK inks. Keep in mind, however, that (1) the 3800 handles the black ink swap automatically, (2) the 3800 uses relatively little ink to perform this swap, and (3) this swap takes only 2 to 3 minutes. You can minimize ink swaps by batching your MK prints together and similarly batching your PK prints together.