Re: Lith film and base density

From: Scott Wainer <smwbmp@starpower.net>
Subject: Re: Lith film and base density
Date: Mon, 08 Dec 2003 00:16:29 -0500

> E-72 contains 1.9 gm and Ansco 130 contains 5.5 gm of potassium
> bromide per liter; would increasing the amount in the E-72 inhibit
> fogging?

Probably, especially because you seemed to have diluted E-72 so much,
and had very little base+fog density with Ansco 130.

> Or would it be better to subsitute benzotriazole for the potassium
> bromide?

I think a small amount (50-200mg/L) of benzotriazole in addition to 1
to 2g/L of KBr in working strength of developer is a good starting
point. So, the amount of restrainer/antifoggants needed is not a lot,
certainly not more than a typical range for standard print developers,
but what I meant is that lith films may give slightly more base fog in
a developer that does not give any noticeable elevation in fog level
with regular printing paper.

Note: film bases can be just plain gray and in that case no amount of
KBr or benzotriazole or anything would reduce that density already
present in the plastic. So as you suggested before, try to fix the
undeveloped film to see if the material is acceptable for the
particular application, before trying all these.

> OTOH Ansco 130 also has the addition of 11 gm of Glycin, a normally
> clean working agent, which I assumed was, in part, responsible for
> the lower level of fog. Any ideas?

You had a lot more KBr in Ansco 130 1+1 than E-72 1+15, so there is no
need for additional explanation for reduced fog level. But presence of
glycin itself does not contribute to reduced fog, especially when
other conditions are adjusted for comparable developing activity.

More generally, I don't think glycin has any mysterious effects like
people seem to read from old literatures. Glycin
(N-methyl-4-hydroxyphenylglycine) is produced as an intermediate in
production of metol (though there are different ways to make metol,
which might be prefered today) but metol is superior in almost every
aspect so glycin is just not used any more, except for some dedicated
followers.

You can increase the amount of KBr in E-72 for regular printing, and
this is probably a good thing if you routinely dilute the developer.

--
Ryuji Suzuki
"Reality has always had too many heads." (Bob Dylan, Cold Irons Bound, 1997)