A roof observed from different lighting conditions or angles may have darker or lighter spots in certain areas. This apparent difference in color is referred to as “shading.” Shading is usually caused by unavoidable slight variations in texture which occur during the shingle manufacturing process.
Black or dark colored shingles are more prone to shading problems. A small amount of light is reflected from dark surfaces. Therefore, even slight textural differences may cause shading. Light colored shingles reflect greater amounts of light than darker shingles and as a result it is harder to notice shading problems. Since blends are made from a number of colors, shading differences are masked and are even less noticeable.
The material on the back of a shingle is sometimes transferred to other shingles that are next to it. Also, when shingles are stacked too high or stored for long periods of time, stains can develop. Both conditions can create the appearance of shading. These are only temporary aesthetic issues and will naturally weather off. Note: Shading does not affect the watershedding performance or life expectancy of a shingle.