Washed Rock Mold

What running water does to stone

Rock on a sea coast or in the bed of a canyon looks different from the same rock on dry land. Water has carried the softer fraction away from it, rounded the edges and, in the places where it swirled around an obstacle, scoured out deep pockets and overhangs. The result is a surface without sharp fractures but with a marked play of shadows, which on a model gives away at once that water flowed here or flows here still. The relief of this mold is made for exactly such places: coastal cliffs, the beds of gorges, banks below a weir, bare rock ledges in a channel.

The longer format and what it makes possible

The area is roughly twice as long as the basic size of the range, so one casting gives a continuous band of rock without a single joint. That suits water above all, where an interruption would show the most: the eye follows the horizontal surface and every vertical joint beside it is conspicuous. Anyone building a longer stretch of bank can alternate the castings turned by a hundred and eighty degrees, so that the same motif does not repeat regularly in the band.

It pays to devote more work to the coloring of such a rock than to a dry slope. Below the surface the stone tends to be darker and greenish from algae, in the zone where the level fluctuates lighter, and higher up dry and dusty again. Three shades applied as a glaze on a damp casting turn a flat area into the depth that no uniform coat of paint can catch up with.

The band of stone is set in place before the water is dealt with. The transparent mass is poured last, so that it leans against the rock and a thin line arises at the bank where the water breaks against the stone and changes color.