The hardness of silicone is usually determined based on the requirements and needs of specific applications. The hardness of silicone is represented by Shore A hardness (one of the commonly used hardness evaluation standards), and the higher the value, the greater the hardness of silicone.

Here are some considerations for choosing the hardness of silicone:

Application requirements: Different applications have different requirements for the hardness of silicone. For example, in applications such as seals or gaskets that require good sealing performance, silicone with higher hardness is usually chosen. In applications that require softness and elasticity, it may be more suitable to choose silicone with lower hardness.

Material deformation and rebound requirements: The hardness of silicone directly affects its deformation and rebound performance. Silicone with lower hardness has better deformability and resilience, making it suitable for applications that require higher deformability. Silicone with higher hardness usually has smaller deformation ability and better stability, making it suitable for applications that require better shape retention ability.
Environmental conditions: It is also important to consider the environmental conditions that silicone will face. Factors such as temperature, chemicals, and ultraviolet radiation may have an impact on the performance of silicone. In extreme temperature conditions, such as high or low temperature environments, higher hardness silicone may be more stable and durable.

User preference: The choice of silicone hardness may also vary depending on individual or specific application preferences. Some users may prefer a soft touch, while others may prefer harder materials.

Taking into account the above factors, the appropriate hardness of silicone should be selected based on the specific application needs, environmental conditions, and personal preferences. When determining the hardness of silicone, it is best to consult a professional or supplier for more accurate advice and guidance.