Mould plastic. This mould can be used to cast concrete, plaster and soap. Weight below indicates the approximate amount of concrete/plaster/soap required. Tip: 1. If the plastic mould will be used to cast concrete, brush it with either cooking oil or liquid latex. 2. To make it easier to remove plaster, heat the moulds using a hairdryer. 3. Removing soap from plastic moulds is easier if the moulds are chilled. Roses 2 pcs Ø 8 cm. 225g/90ml/210g. Depth 3,5 cm.