Polyvinyl Alcohol PVA
PVA (Polyvinyl Alcohol) is a water-based liquid plastic that can be applied to waxed moulds to prevent moulded parts from sticking. PVA is not always required. Often, laminators rely solely on mould release wax to create a surface contaminant on the mould that allows parts to be removed. However, on complicated moulds and on new moulds, when the risk of a part sticking in a mould is greatest, PVA can be applied over a waxed mould.
Apply by brush, paint roller or with spray equipment. PVA often leaves a texture on the surface of the mould after it dries. This texture is duplicated or moulded into the part produced in the mould. For parts that will be painted later, this texture is not an issue. However, for parts that rely on the mould surface to create a smooth final finish, the texture can be a problem.
To achieve the smoothest and least textured PVA coating, apply it with spray equipment. The preferred application technique is to spray a couple of very fine mist coats a few minutes apart, before applying a more generous wet coat over the entire mould. This technique minimizes the likelihood of getting "fisheyes" or imperfections in the coating, and produces a very smooth PVA release coating.