Chemistry of Colors and Curls

Science News, August 25, 2001 by Jessica Gorman

Hair has no fun in sun ... or at beauty salon

Bad hair days have chemical roots. The dyes and perms at a salon, the humidity of lazy summer days, even the routine shampooing, styling, and combing of your hair can foster chemical alterations that do a number on your do.

A cadre of researchers--call them hair scientists--hears your hair screaming. In their lab experiments, these scientists investigate how the natural environment, including sunlight and humidity, changes hair's structure and color. They also identify the microscopic details of unintended damage from styling, dying, and other attempts to beautify hair.

Such work has led the scientists to create new technologies for studying hair damage on the molecular level. But hair research is not only about finding damage--it's also about preventing damage. For example, researchers have found how certain treatments, such as conditioning, help maintain hair's strength and how others minimize color change in dyed locks.

One of the largest sources of hair damage is the quest for beauty. "Nobody is happy with what they have," says Chandra Pande, a biophysicist with Clairol in Stamford, Conn. Brunettes often want light hair. Blondes want to go brown or red. Meanwhile, those with mops of curly hair think their locks are too frizzy, and those with straight manes want curls.

"That's what keeps us busy," Pande says.

Protein makes up about 95 percent of a human hair. The rest is fatty molecules, such as lipids, and pigment molecules. Pande notes that when procedures such as bleaching or perming change the chemistry of hair, they alter the protein-rich internal structure of the fiber. "You can imagine how much damage it does," he says.

In their laboratory, Pande and his colleagues go far beyond imagining such things. Their aim is to determine how different treatments lead to changes in hair. Hair chemists need sensitive methods for recognizing and measuring various types of damage in their effort to identify milder hair products and more-effective treatments, Pande says.

Speaking last May in Towson, Md., at the 34th Middle Atlantic Regional Meeting of the American Chemical Society (MARM 2001), Pande discussed some of the methods that his lab uses to identify hair damage. Since typical human hairs are only 60 to 80 micrometers in diameter, it takes tools as powerful as the scanning electron microscope (SEM) to get a close-up look.

Currently, he is examining the chemical creation of curls in the lab, which depends on disulfide, or sulfur-sulfur, bonds found within hair's protein molecules. During a perm, such bonds are initially broken with a chemical treatment that erases the "memory of the hair," he says. Once hair is held in the desired shape, new bonds are formed with a second chemical step.

Pande speculates to SCIENCE NEWS that some of the lasers he uses to study hair protein might someday be adapted for use in salons. He envisions a day when a stylist might adjust the treatment to maximize the number of disulfide bonds that break during the first stage of the perm and that form during the resetting stage.

He notes that permed hair typically has only 90 percent of the original number of disulfide bonds, leaving the hairdo weaker than before.

On another front, Pande is also developing analytic techniques to understand sunlight-induced damage. This photo-damage makes hair brittle and can alter its color. Molecules of the amino acid tryptophan in the hair, which naturally fluoresce when illuminated, decompose when exposed to the sun's ultraviolet light. Pande has found that a decrease in tryptophan fluorescence from a person's hair can quantify damage from UV radiation.

To protect hair from such damage, researchers also use powerful technology to test potential products. Much of the work of identifying the perfect conditioner or hair sunscreen is done in the secrecy of company labs. However, some of these tests are conducted for consumer products companies by outside researchers, such as the hair scientists at the nonprofit research institute TRI/Princeton in New Jersey.

In one such test, for example, TRI researchers examine how much conditioner remains on hair following rinsing, says K.R. (Ram) Ramaprasad of TRI. As any number of television commercials point out, excessive conditioner buildup can weigh hair down. To see how conditioner coats a hair, Ramaprasad and his colleagues use SEM and a technique called microspectrofluorometry in which the chemists attach fluorescent molecules to the conditioner.

By fluorescently tagging chemicals such as potential additives for shampoos and conditioners, Ramprasad and his colleagues can also tell companies how the compounds penetrate a hair on the microscopic level. Mapping the course that the chemicals take as they penetrate hair fibers helps identify the compounds that cause the least damage.

The TRI group also tries to find out how to get the best results from a promising product. In one case, the researchers have recently been developing computer models to better determine how much of a liquid is needed for an optimal coating. Such models might one day suggest the amount of hairspray needed for the best hold, for example.