Hi Richard,
The developer I use is formulated by Jay DeFehr:
A
Glycol 180ml (heat to
50-600C)
Phenidone 7g
Ascorbic acid 1g
Glycol to : 200 ml
B
sodium carbonate 20% solution
For AGFA Ortho APX25
Working stock 1:1:100; 500ml in a Patterson tank, 200C for 15 minutes
I pinpointed the film to about 10 ASA, another suitable developer is LC-1
formulated by Dave Samaroko, a much lowe B+F but a considerable speed loss :
around 1-2 asa (notes at home, not completely certain)
LC1 developer
5 times stock:
Water 750ml
Metol 3gr.
Sodium sulphite 60gr.
Hydroxyquinone 3 gr.
Sodium bisulphite 15 gr.
Water to make 1 liter
Perhaps adding BZT (benzotiazole) to the developer could help, or
PotassiumBromide…..
Best
Cor
-----Original Message-----
From: pure-silver-bounce@xxxxxxxxxxxxx
[mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of `Richard Knoppow
Sent: woensdag 15 juli 2015 20:27
To: pure-silver@xxxxxxxxxxxxx
Subject: [pure-silver] Re: Update On APX 25 Ortho Print Through
I am very curious about this: what kind of developer are you
using? Some developers, noteably _fresh_ D-76 have no fog suppressor
in them and tend to produce a little fog. Once used the developer acquires
some bromide and some iodide from the film which tends to suppress fog. Kodak
discovered that freshly mixed D-76 would produce very slightly higher speed if
a small amount of bromide was added, about
0.25 gram per liter of stock solution.
Now, what I am curious about is whether fog suppressors have any effect
on the print through. Fog suppressors work because emulsion fog (as opposed to
being lightstruck) come from a different mechanism in the
halide crystals. So, its possible to reduce the inherent fog with
little loss of sensitivity to light. I have no idea what effect the ink
has on the emulsion but some experimenting might be interesting. I
don't suppose the ink is slightly radio active (?)
On 7/15/2015 3:09 AM, C.Breukel@xxxxxxx<mailto:C.Breukel@xxxxxxx> wrote:
Since I also sometimes experienced print through, and had the idea
that it had to do with pressure of the roll in the film back, I
decided to repeat Tim's experiment below. At first I did not see the
imprint, but if you look very carefully one can see the figures and
forms imprinted in both the non-exposed film straight out the wrapper
and a roll of film ran through a Zenzabronica SQ (also non exposed),
The print through is actually lighter than the B+F (which is relative high
due to the home brewn developer I use), so it seems that the black ink used
for the numbers is somehow slightly de-sensitising the film. So it's less
responsive to light, although the density difference is subtle, it can pop up
in the final print.
Then I decided to expose a third roll, deliberately over exposing 1/2-1 stop
from my normal speed (10 ASA) and I took a "busy" subject (an old riveted
steel bridge in the city centre), prints form this test did not show imprint.
I do have to carefully check a few more prints which are currently drying.
Best,
Cor
On 7/7/2015 7:33 PM, Tim Daneliuk wrote:
I developed a couple of rolls of APX 25 Ortho today - One, out of the
box, one, transported through a Hasselblad A12 with no exposure.
Both showed signs of print through. This seems to vindicate Richard
Knoppow's contention that this is an ink/backing paper issue, not a
roller transport or exposure-related problem. So, this would point
to a manufacturing defect that isn't a consequence of use, magazine
pressure, or other after-the-fact artifact.
Interesting.
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