GELATIN LAYERS FOR HOLOGRAPHIC PURPOSES - AN X-RAY-DIFFRACTION STUDY

In order to overcome uniformity problems in large u.v. holoconcentrato rs recorded in dichromated gelatin, the structure of hardened gelatin layers has been studied. X-ray diffraction patterns show that layers a re formed by individual gelatin chains partly associated as triple-str anded helical rods as those found in native collagen. These rods, in t urn, may form fibrillar aggregates. Helical rods and microfibrils are, to a great extent, parallel to the layer surface and their relative a mount and packing depend on the hardener as well as on temperature and drying time after coating. X-ray diffraction offers the possibility o f estimating in a simple manner the relative amount of triple-helical rods in crystallographic register within the gelatin layers. From thes e results, a method for obtaining uniform large holograms by means of a slow layer drying process is proposed.