U of S | Mailing List Archive | alt-photo-process-l | Re: lith film

Re: lith film

both POTA, Technidol and Soemarko LC-1 (Dave used to be on this list, is he still around?) work extremely well with the Ultrafine .007 thick lith films.


Richard Knoppow wrote:
----- Original Message ----- From: "Dave S" <fotodave@dsoemarko.us>
To: <alt-photo-process-l@usask.ca>
Sent: Saturday, September 13, 2008 5:29 PM
Subject: RE: lith film

I also don't at this moment recall the names of official
restrainers, but if you look in the formula books under "soft
working developer", they probably name some.  Or, if he's
around, Dave Soemarko will know....
Goodness, I used to get so much into those stuffs, and I can't believe it that
my memory is fading too. Is it something bromide? maybe potassium bromide? And
then there is another popular restrainer too, but I forgot what that one is. If
Richard Knoppow is around, he will know. :-)


The most common anti-fog agents are potassium or sodium bromide and benzotriazole. The effectiveness of both varies with the pH of the developer. Benzotriazole is supposed to have less effect on film speed for a given amount of fog suppression.
Very low contrast developers depend more on the type of developing agent and pH than on restrainers. The lowest contrast developer is probably Phenidone in a sodium sulfite solution. The well known POTA developer is of this type. Phenidone, and its derivatives such as Kodak Dimezone, are inherently very low contrast and in "normal" developers are usually used with a second developing agent.
The contrast of lith film is mostly a property of the emulsion. Silver halide particals vary in their sensitivity to light, a normal pictorial emulsion, intended to record a wide range of brightness linearly, has a wide range of particals of varying sensitivity. A high contrast film has a much narrower range. While special developers can produce continuous tone negatives from high contast film its always a bit tricky because the film is designed to do just the opposite, that is, to have a sharp demarcation of sensitivity so that just above it will produce maximum density and just below it no density at all. Special developers are used to enhance this effect.
Richard Knoppow
Los Angeles, CA, USA