Recently I've run into excessive spot/speck formation with Platinotype,
both tiny black specks and larger (1mm?) brown ones. They tend to form
late in the coating sequence with a rod, when the sheet is almost ready.
I eliminated Tween 20 from my mix and the problem seems at least greatly
reduced. I suspect that some variation in my current batch of
paper--poor distribution of internal sizing perhaps--was triggering
over-reaction to the surfactant. If you are using any sort of surfactant
in your mix I'd try dropping it. But if the specks you are getting are
all jet black and tiny--not larger and brown--it sounds more like metal
contamination. Do you mechanically clean your sheet with a drafting
brush just before coating? It could help. And if the _brush_ is
contaminated, it could hurt.---Carl