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Home ] What Are Shading and Pile Reversal ]


What Are Shading and Pile Reversal ]

After a plush cut pile carpet has been put into service, the pile direction may begin to change creating an appearance similar to pools of water, or rings of dirt. This is called 'Pooling' and it is a permanent change in the pile directions of which there are no lasting corrections. If this carpet had been installed in another house, it would likely not have pooled. If this carpet were replaced with similar dense plush pile carpet from a different manufacturer, it too would likely pool. If this carpet were uninstalled and installed somewhere else, the pooling would likely disappear. Furthermore, the construction of the carpet, the type of yarn that is used, its color, the method of installation, and the usage and maintenance are also not considered factors in causing pooling.

Pooling is environmentally induced. There is no consensus on what forces actually create it; however there are many theories. Among these are:

  1. the ionization of the atmosphere through central air system
  2. the meeting of cold and hot air masses
  3. foot traffic
  4. alterations in the earth’s magnetic poles.

This ionization of atmosphere was proposed by another inspector,  since deceased, and a solution was to ground the duct work of the central air system. This method may have worked in some cases, but the work was not widely excepted by other inspectors.

The meeting of cold and hot air masses or the movement of air has also been suggested. The photograph below is of a tool used in other trade to follow air masses. It has never been able to show a correlation with the movement of air and pooling.


A compass measures the earth's magnetic poles, and a carpet mill expert have reported that a compass will read forces other than the north pole in areas where pooling is taking place. There has been no verification to  known by this inspector.

The CARPET & RUG INSTITUTE printed a booklet called Pile Reversal ("Shading", "Water Marking")

Disclosure has been the leading argument for deciding who should be responsible when pooling takes place. The crush warranty from Allied and other fiber producers contains disclaimer for pooling and shading. Some carpet mills have allowed a one-time-replacement. To this inspector's best knowledge and understanding, pooling has not been part of the real-estate disclosure for selling or buying a property.

Ray Morgan has written a brochure on this topic and has allowed copy right permission. Click here to view it.

According to the CRI in their publication they say this about definitions.


There is not total agreement in the industry as to what to call these areas or how to define them even though there is agreement regarding the conditions surrounding the phenomena. Therefore, the following International Standards Organization definitions will be used.

Shading -- A change in the appearance of a textile floor covering due to localized alterations in the orientation of the fibers, tufts, or loops. This is not a real change in hue, but a difference in light reflection which can occur as temporary shading, tracking, or pile reversal defined as follows:

Temporary Shading -- A reversible, localized change in orientation of the pile of a textile floor covering during use (sometimes described as a normal characteristic of certain cut pile textile floor coverings).

Tracking -- A gradual change in appearance of a textile floor covering from edge to middle of a narrow band caused by repeated walking over the same area which may result in a localized change in pile orientation and may be irreversible.

Pile Reversal -- An irreversible, localized change in orientation of the pile of a textile floor covering. The phenomenon has different names in different countries.

Below are photographs of situations of pooling. Sometimes this type of pooling is called Shore Lining.

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In this case, the pooling travel under a plastic chair mat.

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Note the serpentine lines in this photo.

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Note the dark line that is beginning to form.

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