I have tried with acidifying the mating bath, but the problem still persists.
Originally Posted by banana_legs
As for the substrate hardness, that's interesting - I just gave my paper a further formaldehyde coating. In this case, is it advisable to rinse the paper after it has hardened, so the formaldehyde doesn't seep into the carbon tissue during mating and harden it?
Attached is a detail of a print where the highlights appear as a white pool - yes, the negative is very grainy, but I would still expect a smoother gradation from light grey to paper white.