When working with addition-cure (platinum-cure) silicone rubber for mould making, avoiding catalyst inhibition is essential for reliable results. This page is for professional makers, hobbyists, and anyone selecting a silicone rubber who needs to understand catalyst sensitivity and ensure proper curing of detailed and durable moulds.

Understanding and Comparing Inhibitor Sensitivity in Addition-Cure Silicones

Addition-cure silicone rubbers are highly sensitive to contamination, and a variety of substances can inhibit or completely prevent their curing process. For successful projects, it is crucial to know which materials and conditions will reliably allow addition-cure silicones to set perfectly, and which will cause costly failures. The primary differences between available products come down to compatibility with base materials, cure timing, and resistance to common contaminants—including various resins, adhesives, pastes, and even residues on casting forms.

The main inhibiting substances typically include certain plastics, adhesives, sulphur-rich clays, tin-cure (condensation) silicone residues, some lubricants, and traces of latex. Even residue from day-to-day handling such as hand creams, industrial solvents, and some natural rubbers can stop catalysis. Professional-grade addition-cure silicone rubbers, such as those from ResinPro, are formulated to minimise this risk, but strict surface cleaning and material choice remain vital for complete curing. By comparing the specific product’s application range and focusing on their inhibitor resistance, users can match the right silicone for their needs and avoid common pitfalls.

Key Factors Affecting Addition-Cure Silicone Catalysis

Successful curing depends on both product selection and surface preparation. Platinum-based addition-cure silicones offer reliable performance when models are free from inhibitor residues. These rubbers are formulated to deliver precise results—even fine details—if cleanliness is observed.

“Pure Mould” – Translucent Liquid Silicone Rubber for Mould Making

The “Pure Mould” – Translucent Liquid Silicone Rubber for Mould Making is a platinum-based addition-cure silicone. Its innovative formulation is designed to resist standard inhibitors when used with properly cleaned forms and compatible materials. With a 1:1 mixing ratio, fast catalysis (3–8 hours), and high mechanical resistance, it is ideal for professional and hobby applications, such as detailed resin and wax casts. Users should still ensure that surfaces are free from sulphur, latex, and oily residues before application.

“Liquid Mould” – Casting Liquid Silicone Rubber, 5–40 Shores, Bi-Component A+B

Perfect for intricate models and technical reproductions, the “Liquid Mould” – Casting Liquid Silicone Rubber is highly suited to casting objects with fine details and notable undercuts. This bi-component system needs careful mixing and catalyst addition. Like all platinum-cure systems, it is important to avoid using on surfaces contaminated with waxes, sulphur, or old tin-cure silicone means. Pay particular attention when using custom models or recycled mould boxes—ensure full cleaning and degreasing to maintain reliable catalysis.

“Liquid Mould” – Casting Liquid Silicone Rubber, 15 Shores 20.8 kg

Engineered for larger-scale or commercial casting, “Liquid Mould” – Casting Liquid Silicone Rubber (15 Shores, 20.8 kg) shares its core mode of inhibition as the smaller format. Both versions are vulnerable to the same contaminants, so proper model preparation—removing dust, solvent, or polymer residues—ensures consistent and reliable curing. Failure to address surface residues is a common cause of catalyst blocking.

“I–Gum” – Non-Toxic Silicone Putty for Mould Making

The “I–Gum” – Non-Toxic Silicone Putty for Mould Making offers a safer alternative for quick, hand-formed moulds, combining a non-toxic composition with easy 1:1 mixing. Although less susceptible to common inhibitors due to its putty form, surface cleanliness is still essential—ensure that no oils, sulphur, or previously used substances are present before mould application for the best results.

Surface Precautions and Practical Tips for Preventing Cure Inhibition

Surface preparation is crucial to reduce inhibition risk. Clean all master models thoroughly, avoiding wooden or polymer surfaces that may retain traces of sulphur, waxes, or old condensation-cure silicones. Where possible, conduct patch tests before full-scale moulding. Choose tools, containers, and release agents specified as platinum-cure safe. If you have previously cast with tin-cure silicone or used unknown substances on your master, consider a sealing coat or gentle abrasive cleaning before proceeding. Avoid latex gloves during mixing and application, as latex is a powerful inhibitor for platinum-based silicone rubbers.

Best Practices for Inhibition-Free Silicone Moulding

Choose suitable addition-cure silicones for your task and always prepare models and workspaces meticulously. Testing on a small area before full pours can prevent waste and ensure your chosen resin or model material is fully compatible with catalyst curing.