CHT QM 258 60 Shore A Moldmaking Silicone, 50 lb

Description

CHT QM 258 Silicone is a two-part, addition-cure moldmaking material for applications that need a firm rubber, controlled dimensions, and resistance to repeated casting. The 50 lb green system is intended for architectural replication, furniture and picture-frame molds, rubber rollers, prototypes, and molds used with polyester, epoxy, rigid polyurethane, or polyurethane foam casting resins. Its 10:1 mix ratio by weight and pourable liquid form support measured batch preparation for production-scale molds.

Where It Fits in Moldmaking

QM 258 is especially useful when a softer mold rubber would flex too much around a large pattern or detailed production tool. The cured material supports architectural features, technical articles, furniture ornament, decorative frames, and casting workflows where dimensional stability matters from one pull to the next. The addition-cure chemistry produces a light green rubber and can cure at ambient temperature. Heat can accelerate the cure when the tooling, pattern, and shop process are suitable for higher temperatures.

Mixing, Degassing, and Cure Control

Stir both components before weighing so settled material is returned to a uniform consistency. Combine ten parts A with one part B by weight in a clean container with enough headspace for mixing and vacuum expansion. Mix until the color is even and no streaks remain. For gravity casting, degassing helps remove entrained air before the silicone is poured around the master. The current technical sheet lists a 60-minute work life at 25 C and a 12 to 18 hour demold window at 23 C. Temperature, contamination, and incompatible mold materials can change cure behavior, so a small compatibility test is sensible before committing a valuable pattern.

Plan the pour path before mixing, especially on tall patterns or molds with narrow details where trapped air can collect. Apply a release system only when it is compatible with both the master and the silicone, and seal porous patterns as the tooling process requires. Pour in a steady stream from one location so the material can rise around the pattern and displace air. After cure, support large mold sections during demolding to avoid unnecessary distortion. When casting aggressive resins, allow the rubber to reach the cure condition recommended in the technical sheet before beginning production. Keep component lids closed between batches, record lot numbers, and avoid swapping A and B components from unrelated lots.

Technical Specifications

Match the batch size to the available mixing and degassing equipment, and weigh both components rather than estimating by volume. Keep tools clean because addition-cure silicones can be inhibited by sulfur, nitrogen, phosphorus, organotin compounds, some clays, and residue from other rubber systems. For related mold rubbers and casting materials, browse our molding materials. The CHT silicone materials resource provides manufacturer background for this product family.

Need Help?

Need help confirming mold compatibility, batch weight, or degassing equipment for QM 258? Call (800) 220-1966 or email [email protected].