Rock Mass Mold

Rock that was not deposited but solidified

Not every rock has layers. Granite, basalt and other rocks of igneous origin came about by the solidifying of a melt, so there are no horizontal bands in them. In place of them a net of irregular crevices appears, massive blocks and faces that break along random directions. For a model that has one practical consequence: such a surface is far more forgiving, because there is no risk that a neighboring casting gives away a mistake with a shifted line. The relief of this mold follows precisely such a structure, that is a large mass with clear edges and deep shadows.

Where it suits and how to work with it

It looks best on large areas: in a mountain face above a line, on a rock spur below a castle, in the mouth of a tunnel hewn in hard rock. The castings can quite happily be broken into irregular pieces, because a fresh break of plaster imitates the natural break of stone perfectly and a joint is then not visible at all. Anyone who wants to get depth lays one piece slightly forward and sinks the other in, so that a vertical groove arises between them.

The pliable material allows a casting to be tipped out undamaged even where the relief has deep pockets. Before the next use it is enough to rinse the mold with water and let it drain, because a settled layer would in time soften the detail. The plaster is poured into the mold mixed thin, so that it fills even the deepest places, and only then is it topped up with a thicker compound.

When composing a tall face it pays off to start from the top. The upper piece decides where the shadow falls and the lower pieces are sunk under it, so the joints stay out of view and are not apparent even when seen from the side.