[pure-silver] Re: Phototec times for Tri-x and Tmax 100
----- Original Message ----- From: "ERoustom" <eroustom@xxxxxxxxxxx> 
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Tuesday, August 26, 2008 6:51 AM
Subject: [pure-silver] Re: Phototec times for Tri-x and Tmax 100 



Hi Janet,
There's no need to develop 120 film any longer than 135 film is there? A 36 exp. roll of 135 film has about the same surface area as a 12 exp. roll of 120. They get same the treatment - or have I 
misunderstood something along the way?
The developing time is affected by the overcoating of the emulsion. Overcoating is a thin layer of gelatin intended to protect the emulsion from abrasion and other damage. The developer must penetrate the overcoat to reach the emulsion. This can change the "induction time", that is, the time it takes after the film in placed in the developer for the image to begin to appear. This time is also affected by temperature in a nonlinear way. That is one reason that developing times vary with temperature at a different rate than is predicted by simple chemical laws. 

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