A carpet or rug may seem to change color in certain areas. Looked at from one angle, these areas appear to be lighter than the rest of the carpet. Viewed from another side, these areas will appear darker. This condition is called shading.
Carpet pile has a natural slope in one direction. As long as the tufts slant in the same direction, the carpet has uniform appearance. However, some of the tufts may slant against this normal pile lay, causing a variation in the way light is reflected from the carpet surface.
Changes in the pile usually develop gradually in traffic areas or in front of frequently used articles of furniture. Shading occurs most frequently on dense, deep, velvety, cut-pile carpets. Many Chinese and dense-pile Indian rugs will show some pile distortion after use or the first cleaning. The problem is also most obvious on single or solid color carpets.
In some cases, shading becomes more apparent after the carpet is cleaned which may lead you to believe that the shaded appearance developed during the cleaning process. But this phenomenon cannot occur overnight, it must develop gradually over time. The shading may not have been visible before cleaning because of lighting, the placement of furniture, or uniform soiling over the entire surface.
Little can be done to prevent or correct shading; it is an inherent characteristic of certain types of carpet and develops over time with foot traffic. It can be slowed by vacuuming or brushing the pile in one direction during daily or weekly maintenance, and by a reliable carpet cleaning or carpet maintenance schedule.
There has also been some study evidence that shading or pile direction can be encouraged by gravity, and electromagnetic currents.