Hi Richard, I thought about the case for color film. Then I got to thinking that if the sensitivity and contrast of professional color film can change and are considered critical why can't the situation be the same for professional B&W. Maybe I am over intellectualizing the problem. ??? Jerry -----Original Message----- From: pure-silver-bounce@xxxxxxxxxxxxx [mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of Richard Knoppow Sent: Friday, October 14, 2005 8:40 AM To: pure-silver@xxxxxxxxxxxxx Subject: [pure-silver] Re: expiration dates on film boxes ----- Original Message ----- From: "Koch, Gerald" <gkoch02@xxxxxxxxxx> To: <pure-silver@xxxxxxxxxxxxx> Sent: Thursday, October 13, 2005 10:45 AM Subject: [pure-silver] Re: expiration dates on film boxes Professional film is treated differently from amateur film, at least by Kodak. Professional films are held after manufacture until their sensitivity and contrast match a standard. Then they are released for sale. Thus a film like TXP is not "fresh from the factory" but it is at a certain known point in its life cycle. This is to insure consistency between runs. In contrast, amateur films are released almost immediately after manufacture. I don't think this is true of B&W film. Kodak states that this is true for color films. Amateur films are made such that the balance and other characteristics are acceptable when fresh and at the expiration date and drift through an optimum at some point in time. Professional films are intended to be stored under refrigeration until use and are designed to have optimum and reproducable balance at the time of purchase. Dealers for the pro products are required to refrigerate them under conditions specified by Kodak. The main issue is color balance which is affected by even slight changes of speed and especially curve shape of the individual layers of the emulsion. B&W film does not have this problem and is in all ways less critical. Some Kodak "pro" B&W films have retouching surfaces on both sides where the amateur film does not. My own experience is that longevity is very brand dependant. For instance, I have a lot of Plus-X sheet film which was bought outdated perhaps 15 years ago. I also have some Agfa APX-10 sheet film which was bought new perhaps 12 years ago. The Plus-X has become slightly foggy. A small amount of bromide added to the developer results in completely clear film edges. The APX-100 is much more foggy. I have not yet tested it with a large dose of bromide but I think it may be unusable. --- Richard Knoppow Los Angeles, CA, USA dickburk@xxxxxxxxxxxxx ======================================================================== ===================================== To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there. ============================================================================================================To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.