Yellowing occasionally appears after professional cleaning of light-coloured carpeting, rugs, upholstery, draperies, or other textile furnishings. This discolouration occurs for a variety of reasons and is usually indicative of another pre-existing problem. The yellowing is not noticeable until after the item is cleaned, either because the dirt was “hiding” it or some latent issue is catalysed by customary cleaning. This is not the fault of the cleaning process.
The customer is often disappointed that the interior furnishing is clean but did not return to its new condition. Occasionally, the yellowing will be in one area but not in another, such as under furniture or in front of a window, where some other condition has initiated the yellowing, only to be exposed by the cleaning method.
Common Reasons for Yellowing
- Photo-Oxidation
Some fibres are prone to photo-oxidation due to normal exposure and use. With ordinary light, sunlight, and atmospheric fumes, certain white fibres, especially when bleached or optically brightened, will eventually begin to yellow. Customary wet cleaning is sometimes enough to induce yellow colouration in white or off-white coloured wool, which was previously damaged by light and atmospheric conditions. - Stain Resistant Chemistries and Early Generation Nylon
On some stain-resistant finishes, silicone-based soil retardant finishes, and early generation nylon, the manufacturing chemistries tend to yellow with age, exposure to UV light, and/or cleaning with a high pH cleaner. - Specialty Finishes
Many textile finishes also yellow with age. These finishes can include flameproofing, crease resistance, insecticides, anti-static treatments, and textile lubricants or softeners, all of which are used on textile furnishings. - Fluorescent Brightening Agents (FBA’s)
Some fluorescent brightening agents can yellow with age and exposure to UV light. These brighteners are found in many detergents, spot removers, and on some white-coloured textiles. - Antioxidants
Antioxidants such as BHT and formaldehyde are found in carpet cushioning, some latex preparations, upholstery foam, carpet backings, and many other common construction materials. These antioxidants redeposit or wick up to the carpet face yarns or fabric surface and yellow on contact with oxygen. - Dyes
Light colours such as beige or tan are often composed of several dyes. Some of these dyestuffs can fade, altering the hue towards yellow. - Forgotten Spills
Long-forgotten spills, stains, and pet accidents can yellow with age. Sugary drink stains and animal urine are common examples. - Soils
Common soil and dirt from normal use can be yellow in colouration. Abrasive action on carpet fibres from normal soiling can also cause permanent discolouration.
Conclusions
There are many possibilities for yellowing, which is more apparent when it occurs on a white or off-white background. A professional cleaner has several techniques available that may reduce the effect of yellowing caused by these conditions. These include treatment with special yellow remover products, bleaches, and adjusting the fibre’s pH to improve its appearance.
Using professional chemicals, yellowing can sometimes be removed, lightened, or improved. However, in many situations, the yellow colouration is permanent.
