Frequently Asked Questions

Why is a specialist rubber mould release agent like Reebaklens RR needed instead of a standard mould release agent?

Standard mould release agents — including oil-based shutter oils and wax-based release agents such as Reebaklens — are formulated for rigid form surfaces (steel, timber, fibreglass) where the form material is not chemically affected by the release agent. Rubber and polyurethane elastomeric mould compounds can be sensitive to certain chemicals in conventional release agents. In particular, some petroleum-based and solvent-based release agents can cause swelling, softening, or degradation of rubber mould compounds — reducing the dimensional accuracy of the mould (swollen rubber produces inaccurate concrete dimensions) and shortening the service life of the mould. Since architectural precast rubber moulds can cost tens of thousands of rupees each, with expected service lives of 50 to 200 casts, degradation of the mould by an incompatible release agent that halves the mould life doubles the effective mould cost per precast unit. Reebaklens RR is specifically formulated and tested for compatibility with rubber and polyurethane mould compounds, providing reliable release without mould degradation.

How should Reebaklens RR be applied to achieve a clean release on intricate textured rubber moulds?

Application to a textured rubber mould requires more care than to a smooth steel form. The release agent must cover all surfaces of the texture — including the recesses, undercuts, and fine detail of the pattern — without pooling in the recesses in a quantity that would fill or blunt the detail and reduce the crispness of the pattern on the concrete surface. The recommended application technique for textured rubber moulds is a soft brush or sponge in a thin, stippling motion that works the release agent into the texture rather than brushing across the surface in a single direction, which can leave uncoated areas in recesses. After applying the release agent, allow it to dry to a thin dry film before placing concrete — wet release agent can migrate into the concrete surface and cause local softening or staining of the paste-rich zone near the mould face.

How many casts per rubber mould can be achieved with Reebaklens RR and when does a rubber mould need to be replaced?

The service life of a rubber precast mould depends on several factors including the rubber compound quality, the complexity of the mould shape, the quality of concrete mix used (aggregate hardness, cement type, water-cement ratio), the care taken in stripping and handling, and the compatibility of the release agent. With Reebaklens RR applied correctly before each cast, high-quality polyurethane rubber moulds typically achieve 100 to 200 casts before significant deterioration of the mould detail and surface. Simple flat-textured moulds used carefully may achieve 200 or more casts. Moulds with deep undercuts, fine detail, or complex three-dimensional shapes typically deteriorate faster because the rubber must flex through greater deformation during stripping. Signs that a mould is approaching end of service life include: visible wear or tearing at fine detail in the pattern; increasing difficulty in stripping without distorting the concrete piece; and reduction in the sharpness and depth of the texture pattern on the concrete produced. Contact Space Arc Engineering for guidance on Reebaklens RR supply and precast mould management.