Reducing bubbles in liquid silicone without a vacuum pump can be challenging, but with some techniques, you can achieve relatively good results. Here are some tips that can assist you in minimizing air bubbles to the greatest extent possible.
liquid silicone bubbles
1. Selecting the Appropriate Silicone Material
Generally, lower viscosity liquid silicone is easier to remove air bubbles, while thicker silicone tends to generate more bubbles during mixing. Based on this characteristic, we can choose the appropriate type and hardness of silicone for the specific application of the project.
The viscosity of RTV-2 silicone materials exhibits the following characteristics:
1. For the same type of silicone, higher hardness results in higher viscosity, which makes it less favorable for bubble removal.
2. Among silicone rubbers with the same hardness but different types: addition-cure clear silicone > condensation-cure silicone > addition-cure translucent silicone.
3. Expired liquid silicone tends to have a thicker viscosity.
2. Extending the Working Time
According to the factors influencing the curing speed of RTV-2 silicone raw materials, we can achieve a reduction in bubbles by extending the working time of the liquid silicone, allowing it ample time to naturally degas. Typically, we can lower the temperature to extend the working time, such as using air conditioning to lower the temperature in the workspace. Alternatively, we can place it in the refrigerator until the degassing is complete before taking it out for curing. However, it is important to note that this method may have some impact on the cured mold and is more suitable for projects with less demanding mold requirements. Additionally, ensure the silicone mixing container is tightly sealed to prevent contact with water, which could affect the subsequent curing process. If it is a condensation-type silicone, the working time can also be extended by reducing the proportion of the curing agent.
3. Pouring Liquid Silicone Techniques
1. One is to apply a thin initial coat of silicone with a fine paintbrush, gently spreading it into all cavities and undercuts (after which more silicone may be poured).
2. Hold the silicone container high above the master pattern (≥40cm) and allow it to flow down slowly in a thin stream. This helps to break up any air bubbles as the silicone flows.
3. Temporarily incline the master pattern at an angle and pour the liquid silicone onto the higher end, allowing it to flow down over the rest of the pattern. Once the silicone reaches the lower end, lay the pattern flat and/or tilt or rotate it as necessary to achieve even coverage.
These techniques can be used alone or in combination with each other.
By employing these techniques, you should be able to reduce the number of air bubbles in the liquid silicone. However, it is essential to note that they might not entirely eliminate bubbles. The most effective method to achieve bubble-free silicone molds is still the use of a vacuum pump.
