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                                                                                                                   Molecular Spectroscopy Project:


1: History        2:Importance and Usage        3: Spectroscopy        4: Current Studies        5: Future Expts.

6: HS Classroom Lesson:        A: Lesson Plan        B: Worksheets        C: Instructor Guide
2. Importance and Usage
    As previously mentioned, the use of Fluorescent whitening agent (FWA) (or the wider category of brightening agents) in textiles became prominent in 1940 (1) as the desire to create brighter (not just whiter) fabrics increased.  Since then, their use in a wide range of consumer products has progressively increased.   Total US consumption of these brightening agents was 100.5 million pounds in 1994.  In 1997, the estimated consumption for 1999 had increased to 116 million pounds (2)The following paragraphs provide more detailed information about the extent and purpose of these brighteners use in some common industrial and consumer products.   

Textiles, Synthetics, and Plastics

Figure 1. Image of several fabrics that have incorporated brightening agents (3).

    In 2006, textiles still accounted for 25% of worldwide fluorescent brightener use (1).  Synthetics and plastics accounted for an additional 5% of total use (1).

    Fluorescent brighteners are typically incorporated into fabrics and plastics via dying during manufacture to "enhance aesthetics and consumer appeal. (4)"  Once incorporated, these brighteners improve coloration and also disguise fading.

    Figure 1 shows the wide range of colored fabrics that can be treated to appear brighter.  Optimally, each fabric and shade is treated with the fluorescent brightener that will best enhance the original fabric's hue or base dye, making it more vibrant.  For example, some brighteners give off highly fluorescent greenish-yellow shades (4) and would be appropriate for green fabrics. 

    For a fluorescent brighteners to be considered particularly effective and useful for use in textiles, it must possess the following three characteristics:

1. fluorescent emission in the desired range (i.e. they give off the correct color) (5,6,7),
2. fastness to washing, perspiration, and sunlight (i.e. they last long because they bond or
adhere well to the base material) (5,6,7), and

3. nonhazardous properties (i.e. humans can be safely exposed to them).


Figure 2. "Color-safe" bleach containing fluorescent
brighteners (8).

chlorox color safe      As brightener use in textiles has increased, US consumption of these brighteners in detergents has also steadily grown over the years.  In 1994, approximately 64.0 million pounds of brighteners were used in detergents, and it was estimated that US consumption of brighteners, in detergents alone, would increase 2 to 2.5% per year (2).  In 2006, detergents accounted for the largest and primary use of brighteners--40% of worldwide use (1).

    Optical brighteners are used in laundry detergent to replenish the inevitable loss of the textile brightening agents that occurs during washing.  In short, washing fabrics with detergent containing brighteners effectively re-dyes the fabric with them.  Most "color-safe" bleach usually contain fluorescent brighteners (See Figure 2).  These detergents are particularly useful for certain fabrics (e.g. wool, silk) which contain FWAs that yellow over time when exposed to sunlight (9); redying with more FWAs can somewhat mask this degradation (10). To accomplish this re-dying, most major detergents contain 0.05 to 0.3% FWAs or brighteners (1).  The FWAs used in detergents are particularly effective in increasing the whiteness of cotton fabrics (2).
    The use of FWAs and fluorescent brighteners has become pervasive, if largely unnoticed by the average person.  The average person has become accustomed to a brilliance and crisp whitness in their clothing that would be impossible to achieve without optical brighteners--"normal," un-enhanced whites and colors may now seem dull or dingy to the modern perception.  
On May 21, 2008, even the Air Force lifted its ban on the use of brightening detergents on Airman Battle Uniforms (ABUs); it had originally imposed the ban out of concern that the increase in brightness caused by brighteners in the detergents would increase visibility to snipers (a hypothesis later shown to be incorrect when tested) (11).   This increasingly widespread use of optical brighteners in textile fabrication and laundering, has not gone unnoticed by the professional drycleaner.  Many drycleaners now boast the use of small, portable blacklights that help "identify fluorescent dyes, oxidized stains, weak areas and unserviceable trimmings (12)."


Figure 3. Paper with FWAs (12).
brightpaper    In 2006, FWA use in paper accounted for 30% of worldwide use (1).   FWAs were first used to whiten paper in Europe; the US also started using FWAs as a way to cut costs while producing paper that was still pleasantly white (the base pulp would not need to be bleached as much). (14).  

    Paper made with FWAs reflects more blue light than normal white light when viewed under light that contains some UV component.  Thus, papers made with FWAs have brighter, more bluish white coloration
(See Figure 3), rather than the true whiteness or cream whiteness of papers untreated with FWAs (15).

    It is worthwhile to note some of the negative consequences to the use of FWAs in paper:

1. The brightness and whiteness scale can no longer be used interchangeably.
     Brightness has is measured using the General Electric (GE) scale, and whiteness is measured using the International Commission on Illumination (CIE) scale.  Both brightness, which is the reflectivity of light in the blue color range, and whiteness, which is the reflectivity of light in all color ranges, were traditionally measured on a scale of 1 to 100 (15).  With the use of FWAs, brightness is no longer as good an indicator of actual white color quality, and additionally, it is now common to have papers that exceeds a whiteness level of 100.  For example, International Paper's (IP) Accent Opaque brand  and Weyerhaeuser's First Choice brand both have a listed GE brightness of 96, but IP's paper has a whiteness is 152, whereas Weyerhaeuser's brand only has a whiteness of 113 (16).

2. The presence of FWAs can make the appearance of printed paper unpredictable.  Because the optical properties of FWAs only become pronounced when the incident light contains UV light, the conditions under which paper is viewed can drastically affect the perceived brightness and whiteness of the paper.  Furthermore, the interaction of print dye with FWA-treated paper is sometimes unpredictable, and papers treated with FWAs are typically "photo unstable" and will often yellow over time, changing the printed colors as the paper ages.  This complicates the decisions made by printers and print buyers (14).

3. The presence of FWAs in paper can reduce its recyclability.  Papers that are saturated with fluorescent dyes (which is what FWAs are) cannot be recycled because it is too difficult to remove the dyes (17).

        Having reviewed the impact of the use of brighteners in a wide range of applications, it is worthwhile to study what spectroscopic properties qualify a substance as a potentially effective fluorescent whitening agent or brightener.  In the next section, the spectra of a few characteristic FWAs will be analyzed to elucidate the common absorption and emission properties of all FWAs.  Click on the button to the right to proceed.

  1. Science Tech Entrepeneur, July 2006 (2006).
    http://www.techno-preneur.net/information-desk/sciencetech-magazine/2006/july06/Fluorescent_brighteners.pdf  (January 7, 2009).
  2. P.V.A. (1997). Fluorescent brighteners. Chemical Market Reporter, 251(4), SR21.
  3. Image of  optically brightened clothes from Meghmani Dyes and Intermediates Limited.
    http://www.pulpandpaper-technology.com/contractors/chemicals/meghmani_dyes/ (April 1, 2009).
  4. Optical brighteners: Improving the colour of plastics. (2003). Plastics, Additives, & Compounding, 5(6), 42-26.
  5. Christie, R.M., Morgan, K.M., & Islam, M.S. (2008). Molecular design and synthesis of N-arylsulfonated coumarin fluorescent dyes and their application to textiles.  Dyes & Pigments, 76(3), 741-747.
  6. Um, S-I., Lee, J-K., Kang, Y., & Baek, D-J. (2006). The synthesis and properties of triazine-stilbene fluorescent brighteners containing the phenolic antioxidant. Dyes & Pigments, 70(2), 84-90.
  7. Um, S.I. (2007). The synthesis and properties of benzoxazole fluorescent brighteners for application to polyester fibers.  Dyes & Pigments, 75(1), 185-188.
  8. Image of Chlorox color-safe bleach. http://www.amazon.com/Clorox-Bleach-Colors-30-3-Ounce-Bottles/dp/B00112PKJW/ref=sr_1_1?ie=UTF8&qid=1238638716&sr=8-1 (April 1, 2009).
  9. Maurdev, G. (2004). The generation of superoxide and hydrogen peroxide by exposure of fluorescent whitening agents to UVA radiation and its relevance to the rapid photoyellowing of whitened wool.  Journal of Photochemistry & Photobiology, 165(1-3), 177-185.
  10. Bloomfield, L.A. (2000). Cleaning agents. Scientific American, 282(4), 108-109.
  11. Brightening detergents OK'd for ABUs. Air Force Times, 68(46), p. 30. June 6, 2008.
  12. P.V.A. (2005). Let there be light. American Drycleaner, 72(2), p. 20, May 2005.
  13. Image of HP Bright White Inkjet Paper.  http://www.shadesofpaper.com/index.php?cPath=61 (March 24, 2009).
  14. Wales, T. (2008). Making it whiter and brighter. Graphic Arts Monthly, 80(7), 34.
  15. Xerox Corporation. (2005).  Demystifying three key paper properties: Whiteness, brightness, and shade. http://a1851.g.akamaitech.net/f/1851/2996/24h/cacheA.xerox.com/downloads/usa/en/t/ThreeKeyPaperPropertiesWhitePaper.pdf (April 2, 2009).
  16. Ducey, M. (2006). Improved paper optics require new terms. Graphic Arts Monthly,78(1), 44.
  17. Russell, N.E. (2008). How to recycle anything. Real Simple, 9(10), 141.