Mold Making RTV Silicone

Molding silicone is widely used across industries such as manufacturing, prototyping, part replication, and composites due to its excellent release properties, dimensional precision, and thermal resistance.Samaro, official distributor of SILASTIC™ RTV silicones from Dow, offers a full range of solutions tailored to demanding molding applications.
Why choose SILASTIC™ RTV silicone for your molding needs?
RTV silicones (Room Temperature Vulcanizing) from the SILASTIC™ range are designed to meet the highest performance standards:

Outstanding detail reproduction, even on complex or delicate surfaces
Excellent thermal resistance, ideal for reusable mold production
Easy demolding, with low adhesion to casting materials
Dimensional stability and controlled elasticity
Wide compatibility with resins, waxes, polyurethanes, plasters, and more

Typical applications of SILASTIC™ molding silicones
SILASTIC™ RTV silicones are used in:

Mold making for industrial, artistic, or decorative parts
Flexible molds for resin casting, composite tooling, and thermoforming
Rapid prototyping and model duplication
Industries including aerospace, automotive, medical, and design

Samaro: your expert in RTV molding silicone
With in-depth technical expertise in molding and reproduction materials, Samaro helps you choose the most suitable SILASTIC™ RTV silicone, considering:

The required viscosity (pouring, brushing, coating)
Pot life and final hardness
Chemical compatibility with casting materials

👉 Looking for a high-performance molding silicone for soft molds, prototype models, or complex shapes?Contact Samaro’s technical team for expert guidance and product recommendations.

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RTV Mold-Making Silicone for Molds, Prototypes and Part Replication

RTV mold-making silicone is widely used to manufacture flexible molds capable of reproducing complex geometries and fine details.

Depending on the selected formulation, it can be used for prototyping, vacuum casting, replication of industrial or artistic parts and selected tooling applications.

Samaro distributes SILASTIC™ mold-making silicones from Dow, together with complementary Synthene, DUNA-Corradini and XIAMETER™ solutions for modelling and molding applications.

Why use RTV silicone for mold making?

The flexibility of silicone makes it particularly useful when demolding complex parts or geometries with undercuts.

Depending on the grade, RTV mold-making silicones can provide:

accurate reproduction of fine details;
low shrinkage;
flexibility suited to demolding;
good dimensional stability;
resistance suited to the selected casting material;
reusable molds for multiple casting cycles.

Actual performance depends on the formulation, casting material, geometry and processing conditions.

Addition-cure or condensation-cure silicone: what is the difference?

RTV mold-making silicones are available with different curing technologies.

Addition-cure RTV silicone

Addition-cure silicones generally use a platinum-catalysed curing mechanism.

They are particularly relevant when very low shrinkage and dimensional accuracy are required, for example in technical prototyping and part replication.

Depending on the formulation, curing can also be accelerated by heat.

Attention should however be paid to potential cure inhibition. Certain contaminants or materials present on the master can interfere with the curing of platinum-catalysed silicone.

Condensation-cure RTV silicone

Condensation-cure mold-making silicones are also commonly supplied as two-component systems, consisting of a base and curing agent.

They are widely used for artistic molding, complex shape reproduction and applications where a different balance of processing characteristics is required.

The choice between addition- and condensation-cure silicone should therefore consider dimensional accuracy, the master material, casting material, processing conditions and potential inhibition risks.

Main SILASTIC™ RTV solutions available from Samaro

SILASTIC™ RTV-4234-T4

SILASTIC™ RTV-4234-T4 is a two-component, addition-cure mold-making silicone particularly suited to prototyping and gravity or vacuum casting applications.

Its low shrinkage and dimensional stability make it relevant for the replication of technical parts.

The system combines a base with the corresponding SILASTIC™ RTV-4234-T4 Catalyst.

SILASTIC™ RTV-4136-M

SILASTIC™ RTV-4136-M is an addition-cure mold-making silicone offering relatively high hardness and good dimensional stability.

It can be used for prototyping as well as architectural, decorative and industrial reproduction applications.

SILASTIC™ RTV-3481

SILASTIC™ RTV-3481 is a two-component condensation-cure mold-making silicone.

Its combination of flow, flexibility and tear resistance makes it particularly suitable for reproducing sculptures, art objects, figurines, architectural details and complex technical parts.

RTV silicone and vacuum casting

Silicone molds are widely used to replicate a master produced, for example, by stereolithography or 3D printing.

Once the silicone mold has been manufactured, polyurethane casting resins can be used to produce prototypes or small production runs with properties selected according to the intended application.

Synthene PR7 resins can be combined with suitable silicone molds for prototyping and vacuum casting applications.

Where are RTV mold-making silicones used?

Typical applications include:

rapid prototyping;
part replication;
vacuum casting;
models and pre-series production;
art and heritage reproduction;
architectural molding;
foundry and lost-wax processes;
selected tooling and composite applications.

The silicone formulation should always be selected according to both the master and the material that will subsequently be cast into the mold.

When selecting a mold-making silicone, I first look at the master and the process: level of detail, undercuts, dimensions, casting material and expected number of reproductions. Hardness, viscosity, working time and curing chemistry come next. Potential inhibition risks also need to be checked before validating an addition-cure silicone. Our role is to consider the complete molding system rather than simply selecting a product reference.

Dorian Bouchardon

Brand Manager for Modelling, Moulding and Composites at Samaro

Visit Dorian's LinkedIn page Discuss your application

How do you choose an RTV mold-making silicone?

Several parameters should be considered.

1. Master geometry

Parts with significant undercuts may require greater mold flexibility to allow safe demolding.

2. Shore hardness

Hardness influences mold flexibility, dimensional support and demolding behaviour.

3. Viscosity

Suitable viscosity helps the silicone flow around details and can simplify casting depending on the master geometry.

4. Working and curing time

These parameters need to be compatible with the volume being prepared and the manufacturing process.

5. Curing chemistry

Addition- and condensation-cure silicones have different processing characteristics and sensitivities.

6. Casting material

Epoxy and polyurethane resins, plaster, wax and other casting materials place different demands on the mold. Compatibility should be checked for the selected system.

7. Expected number of reproductions

Mold life depends on the silicone system, part geometry, casting material, temperature and the stresses generated during demolding.

For a broader overview of available technologies, explore Samaro’s Modelling & Molding solutions.

Our technical team can help you select the silicone, casting system and processing conditions best suited to your project.

How can cure inhibition be avoided with an addition-cure RTV silicone?

The master should be clean and compatible with the platinum curing system. Certain contaminants or materials can interfere with curing. When compatibility is uncertain, testing on a small area before producing the complete mold helps confirm that the silicone cures correctly.

Should mold-making silicone be vacuum degassed before pouring?

Vacuum degassing can be recommended to remove air introduced during mixing and reduce bubbles in the finished mold. Whether it is required and the correct degassing procedure depend on the selected system and should be checked in its technical data sheet.

How should a master be prepared before making a silicone mold?

The master should be clean, stable and free from loose material that could affect reproduction. Depending on the porosity of the surface and the silicone system, sealing or a suitable release agent may be required.

How do you choose the hardness of a mold-making silicone?

A softer silicone generally makes it easier to demold complex shapes and undercuts, while a higher hardness can provide greater dimensional support. Selection therefore depends on part geometry and the amount of mold deformation that can be accepted.

What tests should be carried out before starting a production run?

Testing should check curing, detail reproduction, demolding behaviour, compatibility with the casting resin and mold behaviour over repeated cycles. These trials help qualify the complete system under actual processing conditions.

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