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Story
January 14, 1917
Pine Bluff Daily Graphic
Pine Bluff, Jefferson County, Arkansas
What is this article about?
A photographic method using a blue screen and densitometry assigns numerical color values to metals, with silver at 0 and copper at 50. It detects coloration increases but cannot distinguish pure from standard silver, and barely differentiates German silvers by nickel content.
Clipping
OCR Quality
97%
Excellent
Full Text
A method by which numerical values for the colors of metals has been obtained and described recently in a foreign contemporary. The metal sample is polished with emery, and is then photographed through a blue glass screen. The time of exposure, time of development of the plate, temperature of the developer and all other conditions must be reproduced exactly in order to obtain comparable results. The density of the resulting negative is measured in a Sanger-Shepherd densometer, and the result calculated to a scale in which the color value for silver is 0 and that of copper is 50. The results obtained show that an increase of coloration in the metal does give a higher "color figure," but the method can detect no difference between pure and "standard" silver—silver 92.5 per cent, copper 7.5 per cent—and is only just sufficiently sensitive to distinguish between German silvers having respectively 15 and 7 per cent of nickel.
What sub-type of article is it?
Curiosity
What keywords are associated?
Metal Colors
Photographic Method
Densometer
Silver
Copper
German Silver
Nickel Content
Story Details
Story Details
Method polishes metal samples, photographs through blue glass, develops under exact conditions, measures negative density with Sanger-Shepherd densometer, scales silver to 0 and copper to 50. Detects coloration increases but not pure vs. standard silver differences, minimally distinguishes German silvers with 15% vs. 7% nickel.