Guide to Working with RTV-2 Silicones: Tips and Techniques

Guide to Working with RTV-2 Silicones: Tips and Techniques

Whether you’re an artist, sculptor, or professional involved in mold-making and casting, RTV-2 silicones are likely a familiar material in your toolkit. These versatile materials are widely used across industries like art, sculpture, and industrial prototyping. To achieve the best results and ensure a successful project, understanding the proper techniques for working with RTV-2 silicones is essential. This guide covers everything you need to know about these remarkable materials.

Part A: Safety First

Before diving into the details of working with RTV-2 silicones, let’s cover the basics of safety. As with any chemical materials, it’s important to take proper precautions to minimize risks. Keep these safety tips in mind:

1. Ventilation is Key
   Always work in a well-ventilated space. Adequate ventilation helps dissipate any fumes or vapors released during the silicone casting process. Ensure your workspace has proper air circulation for maximum safety.
2. Protective Gear
   To avoid direct contact with the material, wear safety glasses, long sleeves, and rubber gloves. It’s important to use vinyl gloves instead of latex, as latex gloves can interfere with the curing process of RTV-2 silicones.

Part B: Proper Handling and Storage

To achieve the best results, handling and storing RTV-2 silicones properly is crucial. Here’s how:

3. Temperature Control
   Store and use silicone materials at room temperature, around 73°F (23°C). Using the materials at higher temperatures can shorten their shelf life. Remember that RTV-2 silicones have a limited shelf life and should be used within a reasonable timeframe.

Part C: Applying Sealer/Release Agent

Correctly applying a sealer or release agent is important, especially when working with Tin-cure RTV-2 silicone rubber. Here’s what you need to know:

4. Check Compatibility
   Tin-cure RTV-2 silicone can react negatively with sulfur-based clays, causing the silicone to become tacky or fail to cure. To ensure compatibility, conduct a small test by applying a small amount of silicone to an inconspicuous area of your pattern. If inhibition occurs, use a clear acrylic lacquer as a “barrier coat” to protect the pattern.
5. Release Agent
   Although not always necessary, a release agent can make the demolding process easier, especially when casting on different surfaces. Consider using a release agent to simplify mold removal.

Part D: Measuring and Mixing

Accurate measurement and mixing are critical for a successful mold. Follow these steps:

6. Pre-Mix Part B
   Before mixing, thoroughly stir Part B to redistribute any settled pigments, ensuring a uniform mixture.
7. Precise Measurement
   Use a gram scale to measure the correct amounts of both Part A and Part B. Mix these components for at least 3 minutes, making sure to scrape the sides and bottom of the container several times to achieve a thorough blend.
8. Vacuum Degassing
   To remove trapped air bubbles, vacuum degassing is recommended. Use a vacuum pump that can pull at least 29 inches of mercury (or 1 Bar / 100 KPa). Continue to vacuum until the mixture rises, breaks, and falls. Maintain the vacuum for an additional minute after the material has fallen to ensure thorough degassing.

Part E: Pouring, Curing, and Post-Curing

The pouring and curing processes are critical for the best results. Follow these steps for success:

9. Precise Pouring
   Pour the silicone mixture in one spot at the lowest point of your containment area. Allow the liquid to find its level and flow evenly over the model. Ensure the silicone rises at least 1/2 inch (1.3 cm) above the highest point of the model.
10. Curing Time
    Allow the mold to cure for a minimum of 16 hours at room temperature (73°F/23°C) before attempting to demold. Proper curing ensures the silicone solidifies completely.
11. Post-Curing
    For additional assurance and to remove residual moisture or alcohol, post-cure the mold by heating it to 150°F (65°C) for 4 hours. This step helps ensure full curing of certain urethane resins and rubbers. Let the mold cool to room temperature before use, and avoid curing in temperatures below 65°F (18°C).

Conclusion

In conclusion, working with RTV-2 silicones can be a highly rewarding experience when you follow the proper procedures. By adhering to safety guidelines, handling the materials with care, and following accurate measurement and mixing steps, you can create high-quality molds for both artistic and industrial applications. Enjoy your casting projects and happy molding!