American Photography Volume 14

American Photography Volume 14

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1920 edition. Excerpt: ...focal length, stop /:32, exposure y second, bright light at 12.30 in August, Eastman N. C. film, print on Glossy Velox. PRINT AND PLATE WASHING If it be necessary to wash either negatives or prints for the minimum of time or the smallest quantity of water consistent with safety some means of testing the efficacy of the washing must be employed. For this purpose nothing is better or simpler than the well-known permanganate test, which indicates by color the presence of a very small quantity of hypo. This may be conveniently done by making a stock solution containing one grain of permanganate of potash and ten grains of carbonate of potash to a pint of water. This will be of a rose color, and will remain so for a long enough time if kept well stoppered. To use it, about an ounce of drippings from plates or prints, as taken from the washer, is collected in a clean measure, and a few drops of the permanganate solution added. If any appreciable quantity of hypo is present the pinkness will disappear almost instantaneously; if only a trace remains, it may take two or three minutes to discolor. It is a good plan, until accustomed to the test, to have a check in the form of a glass of clean water to which the same amount of permanganate is added as to the washing water. If this also decolorizes or turns brown it is a sign that the water supply is contaminated with organic matter. In that case a further test should be made with distilled water.--B.J. GRAN'DAD It is a pity this picture was made to fit the embossed mounts instead of being trimmed so that the subject would fit more agreeably into the picture area. It should have been made a little wider and the subject should have been placed a little higher. We notice that only a part of more

Product details

  • Paperback | 344 pages
  • 189 x 246 x 18mm | 617g
  • United States
  • English
  • black & white illustrations
  • 123699325X
  • 9781236993250