Liquid Silicone Rubber for Mold Making (Hard)

1:1 Hard Mold Making Silicone Rubber 30A

Designed for firm, shape-stable epoxy resin molds, this Shore 30A liquid silicone rubber provides more support than soft mould silicone while retaining enough flexibility for demoulding. Its harder silicone body helps moulds hold straight edges, flat bases and accurate dimensions, especially when casting resin pieces that may cause softer molds to bend or spread.

The two-part platinum-cure silicone mixes at a simple 1:1 ratio by weight. Its low-viscosity liquid consistency flows around patterns and detailed surfaces, helping reproduce lettering, textures and small features. Once cured, the translucent rubber has good tear resistance, low shrinkage and a temperature resistance range of approximately -50°C to 180°C.

Why Use Shore 30A Silicone for Resin Molds?

• Firmer silicone, giving better support during resin casting
• Helps reduce mould wall bulging & distortion
• Keeps flat surfaces, corners and edges more accurate
• Suitable for repeated casting when handled correctly
• Flexible enough to release most cured resin pieces
• Low shrinkage helps maintain the original model dimensions
• Translucent finish makes it easier to inspect bubbles and casting position
• Suitable for one-piece molds, open moulds and some two-part mould designs

Common uses include epoxy resin moulds, coasters, trays, ornaments, figurines, prototypes, polymer clay pieces, gypsum crafts, concrete decorations, candles and soap.

Technical Information
Silicone type RTV-2 platinum-cure silicone
Hardness Shore A 30
Mixing ratio 1:1 by weight
Pot life at 25°C Approximately 5-10 minutes
Curing time at 25°C Approximately 4-6 hours
Shrinkage ≤0.3%
Temperature resistance Approximately -50°C to 180°C
Shelf life Up to 12 months when correctly stored

Temperature, batch size and room conditions may affect working & curing times.

How to Mix and Pour:

1. Weigh equal amounts of Part A and Part B using an accurate digital scale.
2. Mix thoroughly, scraping the sides and bottom of the container. Incomplete mixing may leave sticky or uncured areas.
3. Vacuum-degas the mixture if available. This is optional but useful for highly detailed moulds.
4. Pour slowly from one corner in a thin stream, allowing the silicone to flow around the model.
5. Leave the mold undisturbed until completely cured before demoulding.

Because the pot life is short, prepare the model, mold box and tools before mixing.

Platinum Silicone Compatibility Warning: Platinum silicone can suffer cure inhibition when contaminated. Avoid contact with sulfur-based clay, latex gloves, tin-cure silicone, epoxy hardener residue, amines, moisture and incompatible pigments, fragrances or oils. Wear nitrile gloves and test a small area when the model material is uncertain.

Available Pack Sizes
200g set: 100g Part A + 100g Part B
500g set: 250g Part A + 250g Part B
1kg set: 500g Part A + 500g Part B

Package includes: Set of Silicone Part A & Catalyst Part B.