Optical Brighteners

Do you remember the “bluing” liquid that your mom or grandmother used to add to the rinse water when doing laundry? (I might be showing my age by asking.) Bluing liquid made whites whiter, and all your other clothes looked brighter and cleaner too. The blue tint counteracted a fabric’s dingy, yellow appearance.

Although bluing liquid is still available, a fluorescent dye or whitening agent called optical brightener is now used in nearly all laundry detergents and fabric softeners. Optical brighteners reflect the ultraviolet portion of the light spectrum as blue-white light. This is the stuff that made your shirt glow at the roller rink. Because optical brighteners do such a great job in our laundry, it’s very common to find it added to carpet cleaning detergents, as well as spot and stain removers used on carpet.

Do optical brighteners work on carpet?

 Optical brighteners, while useful with laundry, are often associated with the permanent yellowing of carpet. Cleaning agents with optical brightener in them can affect carpet dyes, causing a gradual loss of color over an extended period of time. As optical brighteners degrade, they turn yellow and cannot be removed, leaving your carpet with a yellowed appearance (see photos 1 and 2).

Spot removers with optical brightener in them can sometimes leave a spot that looks purple under normal daylight. They can also leave a permanent lighter-colored halo around the spot. Note the size and shape of these spots, treated with a product that contained optical brightener, when viewed under ultraviolet light (see photos 3 and 4).

Compare these images to the photos of animal urine when viewed under ultraviolet light (see photos 5 and 6).

Detergents containing optical brightener should never be used on your carpet. I cannot think of one carpet manufacturer that allows detergents or spot removers with optical brightener in them to be used on their carpet. In addition, some manufacturers will void a carpet’s warranty if detergents containing optical brightener are ever used on it.

It amazes me that after all these years, and with all the fabulous carpet cleaning detergents and spot removers readily available from reputable formulators, optical brighteners are still found in some of them.

Is optical brightener in your carpet cleaning detergent?

I use a simple test todetermine if carpet cleaning detergents or spot removers have optical brightener in them: Pour some of it on a white coffee filter, then rinse it under running water. I then take an ultraviolet light and direct the light on the filter. If it fluoresces blue-white in color, it has optical brightener in it and should never be used on carpet.

Another tidbit: I often inspect carpet for seam issues, such as fraying and raveling. Many adhesive manufacturers of seam sealer adhesives add optical brighteners to them, so inspectors like me can direct ultraviolet light at the seam edges to see if the edges of the carpet fluoresce a blue-white color (see photos 7 and 8). This allows me to determine if the seam sealer was applied, and, if so, if it was applied properly.

While optical brighteners might make your brights brighter and whites whiter in your laundry, stay away from them when it comes to carpet. Usually, just water or water and a non-lotion dish detergent or hydrogen peroxide will remove most spots.