Having got so far, either by applying or engraving a million granite blocks to the the dam and rail bridge abutments, I’m now attempting to get a suggestion of the mortar in between the blocks to increase the perception and depth of a huge granite wall.
Well, I spent a bit of time on this today, but to no avail, except the surface has dulled down nicely. By far the best relief has been effected by stippling quite a dark grey over the block, letting it dry a bit then dabbing a mix of paler grey and white over, letting that almost dry, then stippling again to blend the shades.
None of that helped render the mortar boundaries. So I’m going to have to think about that again. I did try shaving some black and white pastels onto the surface, then dry brushing the particles in. This has been more effective in the image than in reality. You can see some of the white pastel particles on one side of the wall before they were brushed in.
I’m thinking that the only way will be, setting one surface plane at a time perfectly horizontal and applying a mortar coloured wash and letting it dry before moving onto the next wall surface.