International photographer (Jan-Dec 1934)

Evaporating silver nitrate solutions for crystallizationrepeated until a high degree of purity has been achieved. Consider the steps that must be taken, collateral with the manufacturing process so briefly outlined, to insure the quality of the resulting film support. Samples of all cotton coming into the plant are tested before use. Three potential variables are thus governed. . . . Cotton, before being dumped into the nitrating machines, is accurately weighed. Variables of the nitrating acid, in addition to its temperature and amount, need to be controlled — and tests accomplish this. Nitrated cotton, immersed in water, flows only through tile pipe lines, to avoid contact with metal. In the purification and storage building to which the flow is conveyed under a street and a railroad track, the tanks are made of material inert to the ravaging action of acids so that no impurities may be introduced at this point. The substance inelegantly called "dope" at Kodak Park, after the cellulose nitrate has been thoroughly dissolved by its solvents, actually is the direct culmination in chemical purity of the careful work of hundreds of chemists and skilled workmen ; and the result of study and improvement by two generations of engineers and research scientists. The physical condition of the material, as distinguished from the chemical, becomes evident when one sees the film base winding through the great machine, so flawless and transparent as to be virtually invisible. Cellulose acetate for the "safety film" of home movies and radiography results from : imilarly controlled manufacturing processes at the Tennessee Eastman Corporation's plant in Kingsport, Tennessee, close to the source of supply for raw materials. In the manufacture of "safety film," acetic acid and acetic anhydride are substituted for nitric and sulphuric acids to treat the cotton. Subsequent conversion of cellulose acetate into film base is carried on at Kodak Park, just as in the case of cellulose-nitrate film. While we are close to the subject of cellulose acetate made by Tennessee Eastman for Kodak Park, let's indulge in a conjecture. It is not unlikely that the socks — or the dresses — of persons reading these words are of that very material. . . . Not only film, but also Eastman Acetate Yarn, is made from cellulose acetate produced in the large plant set among the hills of Eastern Tennessee. The yarn mill there, the supplying of acetate for safety glass, the manufacture of Tenite, an acetate molding composition for making combs, automobile fittings, and a large variety of other products — all that is another story. Gelatine is used in large aggregate quantities to suspend the emulsions' silver salts evenly on the film base — but gelatine for photography must be chemically purer than that used for food. Gelatine for Eastman film and photographic paper is produced principally at Kodak Park and by the Eastman Gelatine Corporation at Peabody, Massachusetts. Patient processes of chemical treatment in hundreds of covered concrete tanks prepare animal-hide remnants for cooking. The gelatine, after washings, boilings, filtration, solidfication, blending, and removal of any chance metal content, joins the silver nitrate in the emulsion rooms. It may be interesting to pause now and catalog the most important raw materials of film : cotton from sunny Southern fields ; saltpeter from mines in Chile or produced synthetically from the air in the United States; sulphur from Texas mines ; camphor from Formosa ; wood alcohol distilled from the Tennessee Eastman Corporation's sawmill waste ; hides from cattle that once grazed in Texas or the Argentine; silver from Mexico; and potassium bromide from the Great Lakes brine deposits. The making of light-sensitive emulsions — the layer of film that actually takes the picture — is a highly diversified and extremely delicate process. The Eastman organization, in fifty years of experience, has turned an art depending on chance and mood into an exact science. The genius of pioneering emulsion makers, combined with the manufacturing talent of picked chemical technologists, has established methods by which uniformity is insured to Kodak photo-sensitive materials. The press photographer snaps sharp pictures of racing planes in a thousandth of a second ; the studio photographer makes softly molded portraits with exquisite care. Both require types of film that will faithfully respond to their skill, every time, year after year. Chemical and physical control of silver-salt crystals, together with the addition of extraneous materials, makes emulsions "fast" or "slow," "contrast}-" or "long-scale," A battery of machines converting fluid "dope" into endless sheets of the familiar transparent, flexible film base . . . almost invisible as it passes over the brightly polished rolls that may be seen through the heavy plate glass windows. The scale, the silence, the cleanliness of this operation are characteristic of Kodak Park. Please mention The International Photographer when corresponding with advertisers.