Rough-surfaced papers give much stronger granulated effects as the roughness will exaggerate the granulation. The pigment clings on to the texture of a granulation-friendly surface, like our Cotman Watercolour Paper Pads.
If using the Granulation Medium, be aware that it is also greatly affected by different watercolour papers. For maximum granulation use rough paper; for less granulation use a medium texture surface.
Watch our Masterclass on Granulation for Watercolour here.