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Topic: K19 on silver nitrate?
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Stephen Furley
Film God
Posts: 3059
From: Coulsdon, Croydon, England
Registered: May 2002
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posted 07-16-2002 04:45 PM
Silver nitrate is used in making photographic emulsions, it is used to form the silver halide, mainly bromide, but sometimes also containing chloride or iodide. It is normally obtained as white crystals, which can be disolved in distilled water to give a clear solution. Both crystals and solution will produce brown stains on skin, which are difficult to remove.Since silver nitrate is used in making just about all film stock, except spacing and mag recording stock, but almost none should remain in the finished emulsion, the term 'silver nitrate film stock' doesn't really make any sense. Where did you hear/read this? The only thing I can think of would be either a print on black and white stock, or a colour print using one of the processes where not all of the silver is removed in the bleaching stage. The silver in these prints would have been produced indirectly from silver nitrate, but it still doesn't seem to be a very meaningful name. For anybody who wants to play with silver nitrate, it is easy to make salt prints, similar to those made by Fox Talbot. Make a solution on sodium chloride, common salt, soak white writing paper in it, and dry. In subdued light, brush on a solution of silver nitrate, and dry again in the dark. Do not put the brush back in the nitrate solution after it has touched the paper, as it will contaminate the solution, forming a white precipitate. This precipitate is what you want to form on the paper, but not in the bottle, it is silver chloride. When the paper is dry, expose it in a printing frame, or under a sheet of glass, through a negative, or various objects, leaves, lace etc. several minutes exposure to a source rich in ultra violet will turn the exposed areas brown, I use either sunlight, or the inside of a carbon arc lamphouse. The print can be fixed by washing in several changes of slightly warm water, untill there is no cloudyness in the water. You should now have a salt print - and brown stains on your fingers for the next week or so! Silver nitrate is toxic, and obviously excessive exposure to ultra violet radiation is something to avoid, but with reasonable care, the process is pretty safe.
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John Pytlak
Film God
Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000
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posted 07-17-2002 11:26 AM
Here are some additional links:
http://cameraguild.com/technology/testing_limits.htm
http://www.cinematographer.com/article/mainv/0,7220,34805,00.html The second link is to an excellent article about special process techniques in American Cinematographer called "Soup du Jour". Unfortunately, it may not be accessable as Creative Planet / American Cinematographer upgrade their websites. Recall that the prints of "Minority Report" used both silver retention and Kodak VISION Premier Color Print Film 2393 to achieve their unique look and very rich black level. Here are some additional Kodak articles:
http://www.kodak.com/country/US/en/motion/support/processing/skip.shtml
http://www.kodak.com/country/US/en/motion/newsletters/inCamera/july2000/dark.shtml
http://www.kodak.com/country/US/en/motion/newsletters/inCamera/april2002/ktP.shtml
http://www.kodak.com/country/US/en/motion/newsletters/inCamera/fall98/preview.shtml
http://www.kodak.com/country/US/en/motion/newsletters/inCamera/oct2000/jubaku.shtml ------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: +1 585 477 5325 Cell: +1 585 781 4036 Fax: +1 585 722 7243
e-mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion
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