[pure-silver] Re: old film
----- Original Message ----- From: "Shannon Stoney" <sstoney@xxxxxxx> 
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Friday, April 27, 2007 1:01 PM
Subject: [pure-silver] old film
Hi, I have a couple of boxes of old film. One box is dated 12/2005 and the other 03/2006. It is 4x5 sheet film. It has not been refrigerated all of that time; most of the time it was in a cabinet, but in the air conditioning.
What happens to film as it ages? Does it get more sensitive, or less? Or anything? 

--shannon
I am assuming this is B&W film. Film loses some sensitivity amd sometimes also contrast, and gets foggy. The fog comes from a continuation of the "ripening" process the emulsion undergoes during manufacture. Modern films have substances in them to reduce or eliminate this effect. Fast film is more subject to degradation than slow film. The expiration date on film is the date the film is expected to deliver the same quality as new film, however, its not a sharp cut-off and film is usually good well beyond this date. This film should be virtually the same as new film. I've used film which was ten years out of date with good results and some film that was twenty years out by adding some anti-foggant to the developer and shooting at about half the rated speed. Refrigerating film slows down the chemical processes in the emulsion and extends usable life. However, fast film is also subject to fogging by cosmic rays and cooling does not reduce this effect. I will point out that there is some controversey as to whether the cosmic ray effect actually takes place. Very high storage temperatures can cause fogging but normal room temperatures usually are OK for film life far beyond the expiration date. Unless your film has been subjected to very high temperatures in storage it should be the same as new. 


---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx 
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