[pure-silver] Re: Best developer for fogged film...
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Sun, 6 Dec 2009 19:27:07 -0800
----- Original Message -----
From: "Elias Roustom" <elroustom@xxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Sunday, December 06, 2009 5:30 PM
Subject: [pure-silver] Re: Best developer for fogged film...
XTOL stock @ 70ºF gives a very quick 6.25' for Tri-X.
You can also add potassium bromide to D76 to help reduce
fog. Read this:
http://silvergrain.com/labs/D-76
I'm just looking at charts and articles - and I've hung
around here
long enough. No experience...
Elias
I mentioned this before. In their 1929 paper by Carlton
and Crabtree they described the slight fog created by
_fresh_ D-76 and stated that a small amount of bromide would
increase film speed very slightly by suppressing the fog.
The amount used in the paper, and by Agfa in their version
of D-76 was 0.5 gram per liter but in their special purpose
developer version of D-76 the amount was 0.4 gram, which I
think is closer to the right amount. I think I've seen
another version of SD-28 which specifies only 0.25
gram/liter. Bromide suppresses fog but, if there is more
than the very minimum it will also interfere with the latent
image and reduce film speed slightly.
When D-76 is used some bromide gets into it from the
silver bromide in the emulsion. This also has the effect of
suppressing fog. When the developer is used beyond a certain
point the bromide, and also iodide, also a fog suppressing
agent, begins to reduce shadow detail and effective speed.
Even when the developer is replenished the bromide and
iodide has its effect.
It is common in replenished systems to "season" the
developer, either with old developer or with a specially
compounded seasoning solution so that the developer
performance is uniform from the beginning. This standard
practice for color development.
The Carlton and Crabtree paper is worth obtaining and
reading.
Carlton, H. C. and Crabtree, J. I. 1929. "Some properties of
fine-grain developers for motion picture film," Trans. of
the Society of Motion Picture Engineers, XIII, 406ff.
Ryuji Suzuki has a collection of variations of D-76 on
his web site. According to him the optimum amount of sulfite
and ratio of metol to hydroquinone is somewhat different
than given in D-76. Agfa-17 is closer to the mark. One can
compound a buffered version of Agfa-17 using a borax and
boric acid buffer system as in D-76 but I don't know the
right ratio to duplicate the pH and activity of the
original. Those with a better knowledge of chemistry can
calculate this.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
=============================================================================================================
To unsubscribe from this list, go to www.freelists.org and logon to your
account (the same e-mail address and password you set-up when you subscribed,)
and unsubscribe from there.
Other related posts:
