How to judge whether liquid silicone has been completely cured?

How to judge whether liquid silicone has been completely cured?
To judge whether liquid silicone is completely cured, you can start from the following aspects:
1. Appearance and touch
Dry surface: The surface of fully cured liquid silicone should be dry and not sticky. Touch it gently with your fingers. If there is no residue or sticky feeling after the finger touches it, this is one of the preliminary signs of curing. For example, when making a silicone phone case, when the surface no longer feels sticky, it means that the surface has basically cured.
Color change: Some liquid silicone will change color during the curing process. Please refer to the corresponding information about color and curing degree in the product manual. If the color reaches the color of the fully cured state indicated in the instructions, it usually means that the curing is complete. For example, some brands of liquid silicone are translucent light yellow when not cured, and become transparent and colorless after fully cured.
Increase in hardness: As the curing progresses, the silicone will gradually become hard from a soft liquid. Press with your fingers. If the surface of the silicone only deforms slightly and can rebound quickly, it means that it has a certain hardness and is close to or has reached a fully cured state. For example, a fully cured silicone mold will feel obvious hardness when pressed and will not deform easily.
2. Time and temperature reference
Based on the curing schedule: Each liquid silicone product has its recommended curing time and temperature range, which can be referred to the product manual. Under appropriate temperature conditions, after the specified curing time, it can generally be considered to be fully cured. For example, at a room temperature of 25°C, the manual shows that the curing time of a certain liquid silicone is 24 hours. After reaching this time point, it is likely to be fully cured. However, it should be noted that the actual curing time may fluctuate due to environmental factors.
Temperature influence judgment: Temperature has a great influence on the curing speed of liquid silicone. If the curing temperature is higher than the recommended temperature, the curing time may be shortened; otherwise, it will be prolonged. For example, place the liquid silicone in a heating device and cure it at a higher temperature (but not exceeding the product tolerance temperature). After the shortened estimated time is reached, other judgment methods can be used to confirm whether it is fully cured.
3. Physical performance test
Stretching test: Carefully tear off a small portion from the edge of the silicone product (if allowed) and try to stretch it. Fully cured silicone has a certain elasticity and tensile strength. It will not break easily when stretched and can recover to a shape close to its original shape. If the silicone breaks easily during stretching, or the broken part is sticky and soft like uncured, it may not be fully cured.
Bending test: For some thinner or bendable silicone products, a bending test can be performed. Bend the silicone to a certain angle. Fully cured silicone will not turn white, break, or be severely deformed and cannot be restored when bent. If it turns white obviously when bent and cannot be restored, it may indicate incomplete curing.