Radiography in Modern Industry - Kodak
Radiography in Modern Industry - Kodak
Radiography in Modern Industry - Kodak
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soften considerably with prolonged wash<strong>in</strong>g <strong>in</strong> water above 68°F (20°C). Therefore, if possiblethe temperature of the wash water should be ma<strong>in</strong>ta<strong>in</strong>ed between 65 and 70°F or 18 and 21°C).Formation of a cloud of m<strong>in</strong>ute bubbles on the surfaces of the film <strong>in</strong> the wash tank sometimesoccurs. These bubbles <strong>in</strong>terfere with wash<strong>in</strong>g the areas of emulsion beneath them, and cansubsequently cause a discoloration or a mottled appearance of the radiograph. When this troubleis encountered, the films should be removed from the wash water and the emulsion surfaceswiped with a soft cellulose sponge at least twice dur<strong>in</strong>g the wash<strong>in</strong>g period to remove thebubbles. Vigorous tapp<strong>in</strong>g of the top bar of the hanger aga<strong>in</strong>st the top of the tank rarely issufficient to remove the bubbles.Prevention of Water SpotsWhen films are removed from the wash tanks, small drops of water cl<strong>in</strong>g to the surfaces of theemulsions. If the films are dried rapidly, the areas under the drops dry more slowly than thesurround<strong>in</strong>g areas. This uneven dry<strong>in</strong>g causes distortion of the gelat<strong>in</strong>, chang<strong>in</strong>g the density ofthe silver image, and results <strong>in</strong> spots that are frequently visible and troublesome <strong>in</strong> the f<strong>in</strong>ishedradiograph.Such "water spots" can be largely prevented by immers<strong>in</strong>g the washed films for 1 or 2 m<strong>in</strong>utes <strong>in</strong>a wett<strong>in</strong>g agent, then allow<strong>in</strong>g the bulk of the water to dra<strong>in</strong> off before the films are placed <strong>in</strong> thedry<strong>in</strong>g cab<strong>in</strong>et. This solution causes the surplus water to dra<strong>in</strong> off the film more evenly, reduc<strong>in</strong>gthe number of cl<strong>in</strong>g<strong>in</strong>g drops. This reduces the dry<strong>in</strong>g time and lessens the number of water spotsoccurr<strong>in</strong>g on the f<strong>in</strong>ished radiographs.Dry<strong>in</strong>gConvenient racks are available commercially for hold<strong>in</strong>g hangers dur<strong>in</strong>g dry<strong>in</strong>g when only a smallnumber of films are processed daily. When the racks are placed high on the wall, the films can besuspended by <strong>in</strong>sert<strong>in</strong>g the crossbars of the process<strong>in</strong>g hangers <strong>in</strong> the holes provided. Thisobviates the danger of strik<strong>in</strong>g the radiographs while they are wet, or spatter<strong>in</strong>g water on thedry<strong>in</strong>g surfaces, which would cause spots on them. Radiographs dry best <strong>in</strong> warm, dry air that ischang<strong>in</strong>g constantly.When a considerable number of films are to be processed, suitable driers with built-<strong>in</strong> fans, filters,and heaters or desiccants are commercially available.Marks <strong>in</strong> RadiographsDefects, spots, and marks of many k<strong>in</strong>ds may occur if the preced<strong>in</strong>g general rules for manualprocess<strong>in</strong>g are not carefully followed. Perhaps the most common process<strong>in</strong>g defect is streak<strong>in</strong>essand mottle <strong>in</strong> areas that receive a uniform exposure. This unevenness may be a result of:• Failure to agitate the films sufficiently dur<strong>in</strong>g development or the presence of toomany hangers <strong>in</strong> the tank, result<strong>in</strong>g <strong>in</strong> <strong>in</strong>adequate space between neighbor<strong>in</strong>g films.• Insufficient r<strong>in</strong>s<strong>in</strong>g <strong>in</strong> water or failure to agitate the films sufficiently before fixation.• The use of an exhausted stop bath or failure to agitate the film properly <strong>in</strong> the stopbath.• In the absence of satisfactory r<strong>in</strong>s<strong>in</strong>g--<strong>in</strong>sufficient agitation of the films on firstimmers<strong>in</strong>g them <strong>in</strong> the fix<strong>in</strong>g bath.Other characteristic marks are dark spots caused by the spatter<strong>in</strong>g of developer solution, staticelectric discharges, and f<strong>in</strong>ger marks; and dark streaks occurr<strong>in</strong>g when the developer-saturatedfilm is <strong>in</strong>spected for a prolonged time before a safelight lamp. If possible, films should never beexam<strong>in</strong>ed at length until they are dry.A further trouble is fog - that is, development of silver halide gra<strong>in</strong>s other than those affected byradiation dur<strong>in</strong>g exposure. It is a great source of annoyance and may be caused by accidentalexposure to light, x-rays, or radioactive substances; contam<strong>in</strong>ated developer solution;<strong>Radiography</strong> <strong>in</strong> <strong>Modern</strong> <strong>Industry</strong> 113