
dwin Herbert Land (May 7, 1909 – March 1, 1991) was born in Bridgeport, Connecticut to Harry and Helen Land. His father owned a scrap metal yard. He attended the Norwich Free Academy at Norwich, Connecticut, a semi-private high school, and graduated in the class of 1927. The library there was posthumously named for him, having been funded by grants from his family. He studied chemistry at Harvard. Since the biginning, he was interessed into the study of polarzed light. Much of the light around us is polarized, but our eyes are not sensitive to this quality and can detect it only with the aid of a special filter, such as tourmaline. Thus made visible, polarized light has many uses. Tourmaline, however, is an uncooperative mineral. It is found in nature, but only in small pieces. Edwin Land dreamed of large polarizing sheets, the size of a window, which would open up dozens of new uses. But how could he make such a giant filter? Inspiration came from an old book about the kaleidoscope, that charming toy which looks like a telescope and produces changing colored patterns. In early kaleidoscopes, the patterns were generated by chips of colored glass. Later, Sir David Brewster suggested making the colors by “optical interference” using polarized light. As Edwin Land described it: The kaleidoscope was the television of the 1850s and no respectable home would be without a kaleidoscope in the middle of the library. Brewster, who invented the kaleidoscope, wrote a book about it, and in that book he mentioned that he would like to use the herapathite crystals for the eyepiece. When I was reading this book, back in 1926 and 1927, I came across his reference to these remarkable crystals, and that started my interest in herapathite. Just what is herapathite? It is a crystalline form of iodoquinine sulfate, which, Land explains, was discovered by William Bird Herapath, a physician in Bristol, England, whose pupil, a Mr. Phelps, had found that when he dropped iodine into the urine of a dog that had been fed quinine, little scintillating green crystals formed in the reaction liquid. Phelps went to his teacher, and Herapath then did something which I think was curious under the circumstances; he looked at the crystals under a microscope and noticed that in some places they were light where they overlapped and in some places they were dark. He was shrewd enough to recognize that here was a remarkable phenomenon, a new polarizing material. Doctor Herapath spent about ten years trying to grow these green crystals large enough to be useful in covering the eye-piece of a microscope. He did get a few, but they were extremely thin and fragile—for it is very hard to grow them. What good were these crystals if they could not be grown large enough to use? Because the crystals could lie in every direction, they would produce light rays polarized in all directions—a useless jumble of illumination. Land believed he could solve this problem and, in what might be considered a foolish move, took a leave of absence from Harvard so he could devote full attention to his experiments. In New York City, he invented the first inexpensive filters capable of polarizing light, Polaroid film. Because he was not associated with an educational institution, he lacked the tools of a proper laboratory, making this a difficult endeavor. Instead, he would sneak into a laboratory at Columbia University late at night to use their equipment. He also availed himself of the New York City public library to scour the scientific literature for prior work on polarizing substances. Land attacked the problem in a new—seemingly illogical—way: instead of trying to make the herapathite crystals large, he made them far smaller. He knew that, theoretically, thousands of crystals would function as one if they were extremely small and were lined up with each other. He invented a process for precipitating needlelike crystals about 1 mm (millionth of a meter) long and a fraction of a micrometer wide. The minute needles, almost too small to be seen under a microscope, were made into a thick colloidal dispersion. This substance, of syrup consistency, was then squeezed through long narrow slits. The narrow openings forced the needles to orient parallel to one another, and the substance dried to form a solid, plastic sheet. This became the first large polarizing filter. 











