Dark line around room perimeter, stair edges, under doorways and drapery The effect of doors and windows opening, elevator movement, furnace starting etc. that cause changes in room air pressure. Air is forced into wall cavities or under doors filtering airborne particulate through the carpet fibers. Permanent solution is to seal the walls or floor. Filtration lines are very difficult to clean and can quickly return if the area is not sealed. Interim solution is to spot-clean the problem areas.

Spotty brownish appearance in parts of the carpet. Carpet has been over-wet causing vegetable dye that is present in jute backing to wick to the surface. Acid rinse the carpet or topically spray a souring agent.

Brownish to yellowish discoloration of the carpet or a yellowish color on the tips of the fibers. The moisture in the cleaned carpet pulls residual soil up to the tips of the fibers. Usually occurs in a heavily soil-compacted area or in an area that has taken an extended period of time to dry. Bonnet clean with a mild neutral pH cleaner.

Yellowish to brownish discoloration on the carpet Caused by alkaline residue build-up from cleaning chemicals, improper rinsing of the fibers or ice melting compounds. Test to determine the pH of the carpet. Select an acidic rinse with opposite acidic value to balance the pH at 7

Dark areas or graying in areas which receive the highest level of foot traffic. Scratches and abrasions to the fiber (level loop) matting, flaring or tip compression (cut pile). This is not reversible and is not a warranty item.

Gradually evolving yellow discoloration. Carpet slowly losing its color to a yellowish tinge. Ionic optical brighteners are agents used to convert invisible ultraviolet light to visible light, which increases apparent brightness. Ionic optical brighteners found in some cleaning compounds applied to the carpet Avoid use of ionic optical brighteners. Not possible to reverse once damage is done.

Yellowing of carpet in traffic areas around entrances and exits especially from parking or street areas. Caused by asphalt sealers, tar or oil. Particularly frequent during hot seasons, fresh coatings or from asphalt being dissolved by coolants, gasoline or similar solvents. Very difficult to remove. Use entrance mats to reduce problem. Solvent-based cleaner to remove from the carpet.


Shows as a lighter area on the carpet surrounded by a darker ring. Occurs when liquid is spilled on the carpet. The spill pushes the contaminants that are present in the carpet to the edge of spill where they dry. Extract or bonnet clean with a mild acidic solution.


Carpet appears to have different colored sections. Sometimes looks like a waterline. Fibers in cut pile carpet lie in different directions usually as a result of an installation defect. This is not reversible. Carpet producers do not warranty this.


Carpet has light or dark spots in random locations. Light reflections from a non-obvious light source (e.g. pinholes in draperies, reflection from shiny objects, shiny kick plates in elevators and corners in buildings.) Change light or reflective sources.


Carpet looks worn or old. Reduction in the amount of fiber on the face of the carpet. Replace carpet.

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Author's Bio: 

Graeme Stephens has been running the largest owned carpet cleaning company in new Zealand for 24 years. IICRC qualified "master restoration technician".