I had a play with a broad Signo white pigment pen and a page in my 12×12″ Derwent black page sketchbook… and this is what happened over around three evenings:
I particularly like the ripples – will be doing more of those in the future! The white Signo ink is very opaque, though pens seem to vary in respect of smooth ink flow. I’ve found from experience that if a pen is misbehaving, it’s better to chuck it away. Not necessarily the most cost effective way of managing it, but far less frustrating!