Re: recipe for fine-line developer?

> Subject: Re: Lith Developer formulae... where?
> From: bg174@FreeNet.Carleton.CA (Michael Gudzinowicz)
> Date: 12/7/00 4:19 PM Pacific Standard Time
> Message-id: <90p9eq$np2$1@freenet9.carleton.ca>

> What one sees is that development starts slowly in well exposed
> areas of the film. If a step tablet were used for the exposure, a
> faint image appears in the well exposed areas. Eventually the
> developed area reaches a critical density and semiquinone
> concentration, and then development takes off, and quickly goes to
> completion in that step. Then as development proceeds, the next step
> develops fully.

One thing to note here is that semiquinone only facilitates
development of exposed crystals, or retard development of faintly
exposed crystals, but it does not render unexposed crystals
developable or exposed crystals undevelopable. In lith film/developer
systems that use contrast enhancing agents such as hydrazine
compounds, the latter phenomenon occurs.

Also, the author above mentions "absence of sulfite" but it is not
really true. Free sulfite is present. Indeed, formaldehyde adduct
works as a sulfite level buffer to maintain a low level of free
sulfite in the solution. This is important because you don't want
semiquinone to diffuse too far. A small but nonzero free sulfite
concentration takes care of this problem by breaking down semiquinone
before it goes too far.

--
Ryuji Suzuki
"You have to realize that junk is not the problem in and of itself.
Junk is the symptom, not the problem."
(Bob Dylan 1971; source: No Direction Home by Robert Shelton)