Katherine Burr Blodgett is credited with the invention of the color gauge andnon-reflecting or "invisible" glass. Born in Schenectady, New York, in 1898,Blodgett had an unusual early education. Her mother, widowed just months before Katherine was born, made education a priority for her children. Blodgettattended school in France and Germany and was privately tutored in New York City before attending Bryn Mawr College. She went on to earn a master's degreein physics from the University of Chicago. Upon graduation, Blodgett returned to Schenectady and applied for a position at General Electric Laboratories,where her father had worked as a patent attorney. At the GE laboratory she was fortunate to work with the well-respected Dr. Irving Langmuir, who would later receive a Nobel Prize for his work in chemistry. Dr. Langmuir saw much promise in his young colleague and upon his recommendation Blodgett decided topursue a doctorate degree in physics. She was the first woman ever awarded aPh.D. in physics from Cambridge University. Blodgett's most important work came from her independent research on an oily substance that Dr. Langmuir haddeveloped in the lab. This unusual material was unique in that it formed a film of exactly one molecule in thickness on the surface of water. In 1933 Blodgett made her first breakthrough with the film. She lowered a metal plate into the liquid and discovered that the film would move toward the plate and adhere to it as she raised the plate from the water. In fact, each time she lowered and raised the plate another layer of film would adhere to it. This was the first time a scientist had ever been able to build up layers of moleculesone at a time. Blodgett knew there were practical applications for these built-up layers of film. She observed that the number of layers of molecules accumulated determined the amount of light reflected by the film and concluded that it would be possible to measure the thickness of the film by using the color of the light it reflected. By sealing this film in varied thicknesses within a glass tube, Blodgett could match the color with a corresponding layer ofthickness. This device, called the color gauge, now enables scientists in the fields of chemistry, biochemistry, physics, and metallurgy to measure the thickness of transparent and semitransparent substances within millionths of an inch. Blodgett continued working with what has come to be known as the Langmuir-Blodgett film and in 1938 created non-reflecting glass by applying a thin layer of it to transparent glass. The light reflected by the film canceledout the light reflected by the glass itself, thus rendering the glass invisible. This "invisible glass" has been used in many consumer products from picture frames to camera lenses. Blodgett's invisible glass has also been extremely useful in optics. Because the film eliminates all reflection, it allows 100percent of the light that falls on a lens to pass through it. Previously, eight to ten percent of light falling on a lens would be lost due to the glasslens's reflection of it. Many of today's camera lenses, created using Blodgett's invisible glass, allow photographers to capture all of the available light. The Langmuir-Blodgett film was also used briefly in the process of artificial rainmaking. Though Blodgett found no other practical use for the film before her retirement in 1963, her invention of the color gauge and her method of creating "invisible glass" have assisted scientists in countless endeavorswhich require the measurement of extremely thin substances. Blodgett died in1979 at the age of eighty-one.