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How much silver is there in film?

James Dainis , Jul 28, 2004; 11:51 a.m.

I realize it is usually not viable for the average hobbyist to try to reclaim silver from exhausted fixer. But, I have always been curious as to how much silver is actually in film and photo paper. Also, how thick is the emulsion?

Responses


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Marshall Goff , Jul 28, 2004; 12:38 p.m.

The Bass brothers might be able to alter the price of film, but we'll never be able to change their net worth extracting the silver in it...

Ken Heflinger , Jul 28, 2004; 12:43 p.m.

Agfa Multicontrast Premium contains approx 1.5 grams per square meter (according to their data sheet).

Not sure about film.

Ken

Steve Levine , Jul 28, 2004; 01:39 p.m.

Back in my days at Hollywood Cine Labs in Burbank,CA,I once asked Chuck Kemmerer,my Kodak technical service rep this very question.In an unexposed roll of B&W 35mm motion picture camera film,there is approximately 1 ounce per 1000 feet.A 1000 foot reel of 35mm B&W projection film has around a 1/2 ounce.We used to run old cartoons and scrap B&W films throught the bleach,and fix on the color processor.This would yield almost exactly, a 1/2 once per 1000'.

Donald Qualls , Jul 28, 2004; 03:53 p.m.

And to answer your other question, the full gelatin coating (including subbing layers, antihalation layer, and overcoats) for most modern films runs between 1/1000 and about 3/1000 of an inch, on a base material that runs from around 2/1000 up to 8/1000 (the latter for sheet film, the thin stuff for microfilm that feels like audio tape).

And if you think in metric (I do only when I need to), there are 25.4 millimeters in an inch.

Rowland Mowrey , Jul 28, 2004; 04:39 p.m.

James;

To be more specific, each imaging layer in film or paper runs from 100 to 300 microns thick and interlayers range from 10 - 50 microns. There are also overcoats and undercoats to consider. They will be in the range of 10 - 50 microns as well.

The silver in each layer varies, but the average grain size I have seen published for film emulsion is about 1 micron. Paper emulsions are much finer grained as are print films.

Silver laydown is covers a wide range. X-ray film has as much as 18 grams / sq M, due to being coated on both sides. B&W paper may have as low as 0.9 g / sq M. In color films and papers the grain sizes and sliver laydown in each layer is adjusted for the speed and curve shape. A good average for color paper might be about 1.5 g / sq M on the high side and 0.4 g/sq M on the low side and color film might be 3 - 5 times higher. But this varies quite considerably.

During development, you could use an average of 50% being developed to form the image, and therefore 50% would be fixed out in B&W but all of it would (hopefully) be removed in color.

If anyone out there finds errors in my math, it is because I never used this type of measurement when I made a coating. Other units are used, and I had to do a quick rough conversion.

Hope this helps.

Ron Mowrey

Lex Jenkins , Jul 28, 2004; 10:09 p.m.

James: According to sources I've read, not enough to worry about. Sensitizing dyes and other components are at least as important as silver. The term "silver rich" is just something we like to wax nostalgic over when we look at older photos that seem more original or interesting than our own.

Marshall: That was the Hunt brothers who were obviously misled by the notion that hard assets such as silver, gold, diamonds, etc., are all that's required to play with the big boys. The big boys are mostly old money and have better control over the values of precious metals and gems. The nouveau riche, even Midwestern oil money riche, can get their assets kicked fooling around with old school European money. Even Bill Gates is rumored to be deferential to the less wealthy but well established old money families.

The Bass family in the Fort Worth area is a whole 'nuther breed. Unless someone has information to the contrary I don't see that they've done anything but benefit the community with their wealth.

Rowland Mowrey , Jul 28, 2004; 10:35 p.m.

When silver got to $50/oz, it became of critical importance to the entire photographic industry. One of the raw materials increased in price by 10x. What would you expect them to do, sit on their thumbs?

So, the level of silver went down in some color products by means of increasing coupler reactivity, efficiency of development, and the coupler 'equivalency'. Old couplers required 4 moles of silver to produce one mole of dye, but new couplers required only 2 moles of silver to produce dye.

This move allowed a 50% reduction in silver and it allowed the introduction of the blix.

Ron Mowrey

Andrew Kowalczyk , Jul 29, 2004; 07:19 a.m.

And I always assumed that the silver prices had something to do with introduction of the disk camera. Less silver, more plastic.

Bill Tuthill , Jul 29, 2004; 01:07 p.m.

Blix = combination of bleach and fixer in a single step (right?)


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