Several different factors can cause fabrics to yellow. What is most disheartening to most of your customers is when they store a light colored garment and months or years later pull it out to
find yellow stains, streaks, or an overall yellow cast. Yellowing in storage can be caused by a variety of situations. This bulletin addresses potential storage problems, causes of yellowing of garments, and possible remedies for the problems.
FLUORESCENT WHITENING AGENTS
Optical brighteners or fluorescent whitening agents are applied to fabrics to enhance their brilliance and whiteness. These brighteners can decompose and yellow as a result of heat from drying or steam finishing, bleaching, exposure to light, or long term exposure to atmospheric gases in storage. Natural or artificial light exposure during use or storage is usually only apparent on exposed areas of a garment such as shoulders, sleeves or exposed folds. Unexposed areas such as under the lapels or on the reverse side will remain bright and white. Usually there is no remedy to this problem since optical brighteners or fluorescent whitening agents can not be reapplied to most fabrics. However, on some washable fabrics, a wet cleaning and reapplication of whitening agents will sometimes restore items to a usable condition.
OXIDATION AND YELLOWING OF SIZING
Many cellulose fibers such as cotton, rayon, linen, and ramie are treated with sizings to give the fabric luster, sheen, and hand. Some of the sizings or starches tend to yellow, some more readily than others. Objectional yellowing can occur with age and may be accelerated by the heat necessary for deodorizing and finishing after cleaning. To improve the appearance of this type of yellowing, carefully wet clean the garment. This process may be followed by bleaching in a mild oxidizing bleach such as hydrogen peroxide or chlorine bleach, if necessary.
MYSTERIOUS YELLOW STAINS
Stains from juices, beer, soft drinks, tea, coffee, or other foods or beverages that contain
tannin or sugars can cause stains to develop during storage through oxidation. These stains
were probably invisible when the garments were put away. Once the stain has been left in the fabric, it oxidizes and becomes apparent as time passes. These stains may be very difficult to remove, especially from wool, silk, and nylon. The longer the stain is allowed to age, the more difficult it is to remove. In some fabrics, extensive specialized stain removal agents may lighten the stains enough so that the garment can be returned to a wearable condition.
ACCUMULATION OF WATERSOLUBLE IMPURITIES IN USE AND STORAGE
Discoloration that is confined to the surface of the fabric or areas that have received the greatest exposure to the effects of light and atmospheric soils when in use or in storage is referred to as accumulation of water-soluble impurities. White and pastel fabrics are more prone to showing discoloration from this type of accumulation of soils. To remove this staining, carefully wetclean and soak in a bath of warm water with several ounces of synthetic neutral
detergent and an alkali, such as ammonia. After a short soaking, rinse, extract, and air dry. Do not add ammonia to protein fabrics, such as silk or wool.
SUBLIMATION OF DYE
Some fabric dyes tend to change to a vapor and then transfer and condense onto other articles in use or storage, forming stains, usually in the form of streaks. This type of staining usually develops when a dye sublimation occurs from a dark colored acetate fabric. This discoloration slowly develops over a long period of contact with another article. However, the staining can also develop when items are not in direct contact with one another. Heat may cause this process to occur more easily if a garment is stored in a warm place. In some cases, the staining can be removed by the use of a ten percent solution of alcohol.
When there is an alkaline finish on a garment, exposure to moisture, nitrogen oxide gases, and/or storage in polyethylene bags or film can cause yellowing to occur. With time, nitrogen dioxide reacts with butylated hydroxytoluene (BHT) used in plastic packaging. Research has shown that certain fibers, mainly nylon, is susceptible to this yellowing when contaminated with BHT. Nitrogen oxide gases are formed when air contacts any hot surface, such as a heating furnace, gas or electric cooking range, or any type of gas or electric heater. When these gases contact plastics containing BHT they can cause fume fading on fabrics. This conversion to yellow may be accelerated if there is an an alkaline finish on the fabric. Therefore, the reaction can sometimes be reversed by acidifying the stained areas. This yellowing should not be confused with natural overall yellowing that occurs in some fibers such as wool or virgin nylon. Stains caused by BHT usually form as rings, spots, or streaks on areas near openings, perforations, tears, or holes in the bag or film. IFI’s Garment Analysis Laboratory has been able to reverse this discoloration with the use of a mild acetic acid bath followed by rinsing in cold water. As long as the fabric remains in an acidic state, it is protected from BHT yellowing. To help prevent this yellowing, use ethylene bags that do not contain BHT. Advise your customers that all storage areas should be as free from outside polluted air as possible. Air pollution increases the amount of nitrogen dioxide in the air.