We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
538 Transactions of S.M.P.E., Vol XI, No. 31, 1927
happening is somewhat remote because the surface coating of wax appHed to the film is extremely thin,
3. Effect of Surface Waxing on the Propensity of Film To Show Oil Spots on Projection
It is well known that when film accumulates oil in the projector, the effect of the oil is usually visible on the screen as patches of lesser density than the surrounding portion which is free from oil. The effect of clean oil is to fill up the tiny surface craters, thus reducing light scatter which results in an increased transparency of the film. In the case of dirty oil, or when dirt is applied to clean film treated with clean oil, the oil spotting is greatly exaggerated and such dirty oil produces dark spots.
A study of the surface structure of motion picture film (see Fig. 2) explains why it is difficult to remove oil by mere wiping. The oil sinks into the innumerable craters present on the surface and can only be removed by treatment with suitable solvents.
At the outset it was considered that a waxing treatment might insulate the gelatin surface from the oil and reduce the propensity for oil spots to show on the screen. This was tested as follows:
Film toned with a uranium toner was used for the test because such toned film has a maximum propensity to show oil spots, presumably because of the extremely pitted nature of the film surface. A reel of film was assembled consisting of fifty foot strips treated as follows :
Sample Nature of Film
No. 1 Plain uranium tone
No. 2 Waxed with 5% paraffin in carbon tetrachloride
No. 3 Waxed with 5% solution of 2 parts paraffin and 1 part carnauba
No. 4 Waxed with 1% carnauba and overcoated with 5% paraffin
No. 5 Waxed with 1.5% candehlla and overcoated with 5% paraffin
Preliminary tests to determine the rate of solution of cold waxes and mineral oil indicated that carnauba and candelilla waxes were more impermeable to oil than paraffin, so that in the above double coated tests the object of the first coating of carnauba or candelilla wax was to protect the film against oil, while the coating of paraffin was to secure maximum lubrication.
A good grade of light machine oil was splashed in liberal quantities on all the samples while the film was being wound from one reel