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.
> -----Original Message-----
> From: Erie Patsellis [mailto:email@example.com]
> Sent: Sunday, September 14, 2008 9:09 PM
> Cc: firstname.lastname@example.org
> 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.
> Richard Knoppow wrote:
> > ----- Original Message ----- From: "Dave S" <email@example.com>
> > To: <firstname.lastname@example.org>
> > 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
> >> 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
> > 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
> > email@example.com