Silicone Addition Colorless 25 – Platinum Silicone for Strong Molds & Finished Products

Premium Platinum Silicone for Professional Molds and Finished Products

Silicone Addition Colorless 25 is a two-component, platinum-cure (addition-crosslinking) casting silicone with Shore A 25 hardness and exceptional mechanical properties. This high-performance silicone combines high tensile and tear strength (7 N/mm² and 30 N/mm²) with extreme elongation (>420%) and minimal shrinkage (<0.1%), ideal for durable molds and strong end products. It flows easily, vents easily, and is perfectly colored with silicone colorant. Simple 1:1 mixing ratio.

Key Benefits

• Exceptional mechanical strength: 7 N/mm² tensile strength and 30 N/mm tear strength for durable molds that can handle hundreds of castings
• Extreme stretchability: >420% elongation for flexible applications without cracking or permanent deformation
• Shore A 25 hardness: Optimal balance between flexibility and stability for versatile applications
• Platinum-cure technology: Minimal shrinkage (<0.1%), no inhibition on most substrates, long service life
• Good fluidity and self-venting: 3,900 mPa·s viscosity for excellent detail reproduction without vacuum treatment
• Perfect coloring: Transparent with a light yellowish glow, excellent for coloring with silicone dye for intense colors.

Typical Applications

• Strong, durable molds for concrete, cement and WetCast precast elements
• Props, masks and flexible decorative elements for SFX, film and theatre
• End products and prototypes where high mechanical strength is required
• Pad printing stamps and flexible printing applications in the graphics industry
• Podiatry applications and medical models with a balance between softness and firmness
• Jewelry molds, design objects and industrial applications

Technical Features

Basic specifications:

• Type: 2-component platinum-cure silicone (poly-addition)
• Mixing ratio: A:B = 100:100 (1:1 by weight)
• Pot life: 30 minutes at 20°C
• Degrindable: 3-5 hours at 20°C
• Viscosity: 3,900 mPa·s at 20°C
• Hardness: Shore A 23-27
• Tensile strength: 7 ± 2 N/mm²
• Tear strength: 30 ± 2 N/mm
• Elongation: >420%
• Shrinkage: <0.1%
• Density: 1.03 g/cm³ at 20°C
• Color: Transparent with a slight yellowish glow

Processing instructions:

1. Mix components A and B carefully in a ratio of 100:100 (1:1 by weight) by hand or machine.
2. Stir slowly in a figure-8 motion to avoid entraining air.
3. Process the mixture within the pot life of 30 minutes
4. Wait until the whole has completely hardened before de-moulding (3-5 hours at 20°C)
5. Curing can be accelerated by heating - every 10°C increase in temperature roughly halves the time

Customization options:

• Reduce hardness: Add silicone oil (note: migrates to surface over time)
• Thickening for spatula: Add Silicone Thixo A or fumed silica
• Coloring: Use silicone colorant for intense colors

Silicones and More supplies high-quality silicones for professional mould making, SFX, industrial applications and strong end products.

Important Warning: Inhibition with Additive Silicones

Note: This is an addition silicone (platinum cure). These silicones can be poisoned by sulfur, nitrogen, amino compounds, and metal salts. If you're unsure whether the products you use (including gloves, spatulas, and cups) contain these ingredients, perform a small test first. These substances are found in many latex gloves, some plastilines, paints and adhesives, condensation silicones, one-component silicone sealants, natural rubbers, and 3D printing materials (especially stereolithography). If you do decide to use it, you will need to apply a protective layer of polyvinyl alcohol (PVA) .

Professional Support

Our technical specialists advise on material selection, processing techniques, coloring, and optimal results for your specific mold or end product application. Contact us for technical data sheets, processing guidelines, or advice on inhibition prevention with addition silicones.