What is the reason for bubbles when screen printing high-gloss silicone cover?

What is the reason for bubbles when screen printing high-gloss silicone cover?
The root cause of bubbles when screen printing high-gloss silicone cover is mainly related to factors such as silicone ink characteristics, operating process, environmental conditions and substrate status, as follows:
Silicone ink characteristics
Formula and ingredients: If the proportion of each component in the formula of high-gloss silicone cover is unreasonable, bubbles may be generated. For example, if the proportion of curing agent is too high, the curing speed of silicone will be accelerated, and the chemical reaction produced during the curing process will be too intense, and the gas will not be able to be discharged in time to form bubbles. In addition, the compatibility of some additives in silicone is not good, and gas may also be released during mixing or curing.
Viscosity problem: If the viscosity of silicone ink is too high, the fluidity will deteriorate. During the screen printing process, it is difficult for air to escape from the silicone and it is easy to be wrapped inside the ink to form bubbles. Moreover, high-viscosity silicone ink is more likely to involve air when stirring. On the contrary, too low viscosity may cause the silicone to flow after printing, resulting in uneven surface and may also introduce bubbles.
Operation process
Improper stirring method: When mixing silicone, if the stirring speed is too fast, a large amount of air will be involved in the silicone. Even if it is left to stand for a certain period of time, it is difficult to completely eliminate these bubbles. Moreover, uneven stirring will lead to inconsistent local composition ratios of silicone, affecting the curing effect and increasing the possibility of bubble generation.
Printing speed and pressure: When screen printing, the speed is too fast, and the silicone ink will pass through the screen quickly. The air will not have time to be discharged and will be wrapped in the ink to form bubbles. If the printing pressure is too high, the silicone ink will be squeezed between the screen and the substrate, and the air will be forced into the ink. On the contrary, too little pressure may lead to insufficient ink transfer, forming gaps, and air will enter and form bubbles during the subsequent drying process.
Multiple printing connection problems: If the high-gloss cover silicone is printed multiple times, the interval time between each printing is not appropriate, and the previous layer of silicone is not completely dried and cured before the next printing, which may prevent the internal air from being discharged and produce bubbles. Or the surface of the previous layer is uneven, which will also introduce bubbles in subsequent printing.