I had one more day at St Abbs. The evening before, I planned an experiment. I would cover the paper in a simple wash and build in the shape of the jutting rock simply using white and sepia ink for the guano and shadows and teeming birds in the air and dotted on the sea. The rest would be left with the wash showing through.
As the rock became submerged, it took a muted golden hue as shown. I photographed this on site (lower image) before the next drastic step of putting in the shadow and reflection (upper image). I think this deeper tone was needed to ground the rock but on reflection it should have been done more delicately. I unintentionally obscured the fractal line made by the yellow spreading into the blue wash.
For completeness, this was my first attempt.