I see. I'm not familiar with your HP printer, but my HP 5550 uses a #56
cartidge for black and it uses pigmented ink. A quick wet test (a wet
finger) on a couple of inkjet plain papers (Tesco 90gm and that Rey 90gm)
shows some light smearing, i.e the paper around the text goes light grey but
the text is still bold and defined. There are some more expensive lightly
coated plain papers that may do better.