RE: lith film
Yes, I am still around. :-) I admit that I don't check all messages as I used to, but the title "Lith Film" caught my attention. I still read paper sizing, gum, or carbon threads though. I guess in general I am still very interested pigment-colloid processes. Dave S > -----Original Message----- > From: Erie Patsellis [mailto:erie@shelbyvilledesign.com] > Sent: Sunday, September 14, 2008 9:09 PM > Cc: alt-photo-process-l@usask.ca > Subject: 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. > > erie > > 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. :-) > >> > >> > >> Dave > >> > > 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 > > dickburk@ix.netcom.com > > > > > > >
|