The presence of one or a few very small defects is not visually observable. Increase the number of defects to millions, and they collectively diffract light to create visible cloudiness in optical discs. An analogy is clouds in the sky that consist of millions of water vapor molecules. One or a few molecules are not visible, but millions of them are collectively observable as clouds in the sky. Similar effects result in visible clouds in optical discs.
Defects regularly occur during the mastering and molding process.
Random, isolated defects are easily corrected in the C1 circuitry. Dense defects may generate cloudiness and can cause severe interchange problems. One source of clouds are the multiple separations required during mastering and molding. The father is first electroplated onto a metallized glass master. After separation, cleaning, and surface passivation, nickel mothers are electroplated onto the father.