Poisonous Substrates

When it comes to mold making, silicone is a versatile material that offers various options. Two popular types of silicone used for mold making are platinum-cured and tin-cured RTV silicone. Understanding the differences between these silicone types is crucial in choosing the right option for your mold making projects.

Platinum-cured silicone gets its name from the catalyst used to cure the silicone: platinum. This type of silicone offers several advantages, including longer library life, FDA compliance for food and skin contact, and high heat resistance. On the other hand, tin-cured silicone, as the name suggests, uses tin as the catalyst for curing. It is generally less expensive than platinum-cured silicone.

Whether you're casting molds for intricate designs or creating molds for functional parts, understanding the unique properties of each silicone type is essential. From curing processes to shrinkage and compatibility, this article explores the key differences between platinum and tin-cured RTV mold making silicone and provides insights into their specific applications and considerations.

Platinum-cured siliconePlatinum-cured silicone

Key Takeaways:

  • Platinum-cured and tin-cured RTV silicone are two main types of silicone used for mold making.
  • Platinum-cured silicone offers advantages such as longer library life, FDA compliance, and high heat resistance.
  • Tin-cured silicone is generally less expensive than platinum-cured silicone.
  • Consider factors such as silicone shrinkage, production life, and temperature and chemical resistance when choosing between the two types.
  • Compatibility with casting materials and post-curing procedures are also important considerations in mold making.

Silicone Properties and Uses

Silicone rubber is a versatile material widely used for various applications, including mold making. Its outstanding properties make it an ideal choice for creating high-quality silicone molds.

One of the key advantages of silicone is its strength and flexibility. It can withstand considerable stress without losing its structural integrity, making it highly durable for long-lasting molds.

Moreover, silicone exhibits self-releasing characteristics, which means that it easily releases castings without the need for excessive force or mold release agents. This property simplifies the demolding process and ensures clean and precise reproduction of intricate details.

When working with silicone molds, it is important to consider factors such as silicone toxicity and the use of food-grade silicone for applications involving food or skin contact. Using food-grade silicone ensures safety and compliance with regulations, providing peace of mind for projects involving culinary creations or skin-friendly products.

In addition, mold release agents can be employed to further facilitate the demolding process. These agents create a barrier between the mold and the casting material, preventing adhesion and allowing for easy separation.

To enhance specific properties of silicone, various additives can be incorporated. For instance, additives can improve the flexibility of silicone, enabling it to conform to intricate shapes and contours effectively.

Overall, silicone's exceptional properties, including strength, flexibility, self-releasing characteristics, and the ability to incorporate additives, make it a preferred choice for mold making applications.

Advantages of Silicone for Mold Making:

  • High strength and flexibility for durable molds
  • Self-releasing properties for easy demolding
  • Food-grade silicone for safe use with food and skin contact
  • Mold release agents for effortless separation of castings
  • Additives to enhance flexibility and improve mold performance

Curing and Inhibition of Silicone

All silicone rubbers can be subject to cure inhibition, especially when contaminants are present on the surface of the model being used for mold making. It's important to understand the factors that can affect the curing process and how to prevent cure inhibition to ensure successful mold creation.

Cure Inhibition in RTV Silicone Processes

Cure inhibition refers to the condition where the silicone does not fully cure, resulting in a tacky or sticky surface that cannot be demolded properly. This can be frustrating and impact the quality of your mold. It's essential to identify the potential causes of cure inhibition and take the necessary precautions.

One common cause of cure inhibition is the presence of sulfur. Platinum-cured silicone is particularly sensitive to sulfur and will not cure when exposed to it. Therefore, it is crucial to avoid using sulfur-containing materials or working in environments with high sulfur content when using platinum-cured silicone. Sulfur is contained in some clays so if you are planning to create a mold of modeled clay that contains sulphur you will need to seal the surface so that silicone does not come into contact with it.

On the other hand, tin-cured silicone can cure over models containing sulfur if the surface is properly prepared. Applying an acrylic spray on the surface can seal off the sulfur, allowing the silicone to cure without inhibition.

Silicone Mold Release Techniques

In addition to curing inhibition caused by sulfur, certain substrates and adhesives can also lead to inhibition in platinum-cured silicone. It's important to ensure compatibility between the silicone and the materials it meets. Testing a small amount of the silicone on the intended substrate can help determine if any inhibition issues might arise.

Furthermore, using effective mold release techniques can help prevent cure inhibition. Mold release agents create a barrier between the silicone and the substrate, preventing any contaminants from interfering with the curing process. Applying a thin, even layer of a suitable mold release agent can significantly reduce the risk of cure inhibition.

Cure Inhibition Caused by Poisonous Substrates

It is worth noting that cure inhibition can also be caused by poisonous substrates. When working with substrates that contain poisonous materials or residues, it is crucial to take appropriate safety precautions, such as wearing protective gloves and working in a well-ventilated area.

Understanding the causes of cure inhibition and implementing preventive measures can help ensure successful silicone mold making. By taking the necessary steps to avoid cure inhibition, you can create high-quality molds that produce the desired results.

Poisonous SubstratesPoisonous Substrates

Shrinkage and Library Life of Silicone

One of the key factors to consider when choosing between tin-cured and platinum-cured silicone for your mold making projects is the issue of shrinkage. Shrinkage refers to the change in size that occurs in silicone molds over time. It is a critical consideration as it can affect the accuracy and integrity of the final castings.

Tin-cured silicone molds generally exhibit higher levels of shrinkage compared to platinum-cured silicone molds. This means that over time, tin-cured molds can experience dimensional changes that may result in inaccuracies or distortions in the castings.

Moreover, the library life of silicone is an important factor to consider. The library life refers to the longevity of the silicone molds, especially if you plan to reuse them for multiple castings over an extended period.

Tin-cured silicone molds typically have a limited library life, typically around 12 months. This means that after this time, the molds may start to degrade or lose their dimensional stability, resulting in reduced casting quality.

In contrast, platinum-cured silicone molds have a much longer library life, measured in decades. These molds offer extended usability and durability. With proper care and maintenance, platinum-cured silicone molds can retain their dimensional accuracy and produce high-quality castings for many years.

Moreover, the shelf life of platinum and tin silicone also differs. While both types of silicone have a finite shelf life, tin-cured silicone tends to have a shorter shelf life compared to platinum-cured silicone. This means that tin-cured silicone may have a shorter expiration date and may need to be replaced more frequently.

Shrinkage Comparison between Tin-Cured and Platinum-Cured Silicone:


Tin-Cured Silicone

Platinum-Cured Silicone


Higher levels of shrinkage

Lower levels of shrinkage

Library Life Comparison:


Tin-Cured Silicone

Platinum-Cured Silicone

Library Life

Approximately 12 months

Measured in decades

Understanding the shrinkage and library life of silicone can help you make an informed decision when selecting the right type of silicone for your mold making projects. Consider the specific requirements of your application and the longevity you need from your molds to ensure successful and durable end results.

Production Life and Application Specificity

The production life of silicone molds is an essential consideration when it comes to mold making. It refers to the longevity of the molds for casting various materials and can vary depending on different variables and application-specific requirements.

To ensure the best results and maximize the production life of silicone molds, it is crucial to follow certain best practices for curing. These practices include proper mixing ratios, adequate mold release agents, and appropriate post-curing procedures. By adhering to these practices, you can enhance the durability and performance of your silicone molds.

When it comes to mold making, platinum-cured silicone offers distinct advantages in terms of production life and application specificity. Platinum silicone mold making techniques can ensure

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