Modroc (or Modrock ) is plaster bandage that is used for modelling, casting and crafting.
So how did it come about that a medical product began to be used in this way?
Many years ago, somebody in the theatrical trade had an urgent problem. He had to make some simulated rocks for a set quickly. He had a brain wave (or, perhaps in the past he had broken a leg and had it plastered with plaster bandage). The upshot was that he got hold of some plaster of paris bandage, made an armature (rough shape onto which to model) out of chicken wire andmodelled the Plaster bandage onto it. When it had dried sufficiently, he painted his simulated plaster rocks and the set was ready for the production.