Burlap is used in mold making primarily as a reinforcing layer to add tensile strength and reduce weight. It can be used with plasters like Ultracal or Hydrocal to create strong yet lightweight mother molds or mother mold shells, by layering wet burlap strips dipped in the plaster mixture and pressing them onto the mold. It's also used in composite molding by layering it with resin to create rigid parts.
