A photo of the beautiful topographical pattern of a piece of flint stone in the National Museum of Denmark in Copenhagen.
I love the jagged edge on the left. Nodules of flint are usually found in chalk cliffs. I’m figuring the chalk could be formed by using pure spackle mixed with matte medium. The sheen of the inner exposed rock would be semi-gloss acrylic. The stone itself could be done in watercolour using the wet-on-wet method.
Flint-Inspired watercolour painting in progress.
Spackle/acrylic mix laid down along with ‘iron’ paint and rusting solution. Black background painted in with acrylic. Wet-on-wet watercolour of rock.
The ‘topographic‘ map of the stone is painted in. Initially the topographical lines were way too dark so I brushed it back but I still didn’t like it. 
So it was on to Plan B: using acrylic over top. I like this a lot better: the cut surface of the stone is done in glossy medium; the chalk matrix in matte medium. A minor problem was that the spackle marked very easily any time something rubbed against it; this was solved by coating it with matte medium, although I needed to create a relatively dust-free environment to put on the medium.
Topographical Flint, acrylic & spackle on watercolour paper, mounted on birch plywood, 16″ x 12″.
