Bubbles in liquid silicone during the mold opening process can seriously affect the appearance of silicone molds, which makes us feel helpless, especially for those without a vacuum machine. Below, we will share the tips for reducing silicone bubbles in molds without a vacuum machine.

Firstly, we analyze the reasons for the formation of bubbles. The first reason is that the bubbles brought in during the mixing of silicone and curing agent were not completely eliminated. Therefore, when stirring, we need to stir in one direction and let the bubbles float up on their own after stirring.
Secondly, when pouring glue, it is best to let the liquid silicone slowly flow down in a filiform, which can eliminate bubbles while pouring glue. After pouring, the bubbles on the surface can be punctured with a toothpick.

In addition, we can also extend the curing time by controlling the ratio of silicone to curing agent to buy time for the natural discharge of bubbles. For example, if the ratio of silicone to curing agent is 4%, we can reduce it to 2%. This will increase the crosslinking time of silicone in the early stage of the mold, and the air in the mold will slowly be discharged to achieve the goal of reducing bubbles.

The second reason is that the formula of liquid silicone raw materials contains a small amount of volatile impurities, which can easily vaporize and form bubbles during heating and curing. Therefore, we try to use room temperature curing or low-temperature baking during curing to let these impurities evaporate first, which can reduce bubbles.

Some mold makers are also accustomed to adding silicone oil to dilute the silicone to increase the fluidity of liquid silicone and facilitate the elimination of bubbles (low viscosity silicone is easier to exhaust bubbles). However, we suggest that the maximum amount of silicone oil added should not exceed 5%, as excessive silicone oil addition can damage the molecular weight of the silicone, resulting in silicone molds that are not resistant to acid, alkali, and aging.