slightly purple Tri-X ?

Dan Quinn wrote:
Donald Qualls wrote

Dan, it's classic because it was done that way, regularly and
routinely; it was the ability to process that way, in a hotel
with no darkroom to get negatives and then print (portable
enlarger) in the bathroom with a towel under the door that
made monobaths popular for around 20-30 years (until
Polaroid got the quality and image size to
beat them out).



I was born too late. I missed the hay-day of mono-bath in
cassette developing. In the late 50s I used a Yankee and my
friend used a Nikor.

Not born too late, I think -- I first read about monobaths in Popular
Science, in the late 1960s (when they were already on their way out).
More likely you just weren't in photojournalism, or not in a "time to
print" environment where monobaths would have had advantages over
conventional rapid processes like HC-110 A and rapid fixer, which can
get you from camera to wet printing in not much over fifteen minutes --
the advantage of a monobath over that is you don't have to load the film
on a reel (for in-cassette processing, anyway), and don't need to carry
two or three kinds of chemicals, just the monobath powder (the other
reason monobaths typically haven't been based on rapid fixer -- they'd
have to be liquid, since ammonium thiosulfate is always packaged and
sold as liquid).

I think the first time I ever learned of that technique must have
been 94 while reading Steve Anchell's Monobaths and In-Cassette
Processing in the May 1994 issue of Camera & Darkroom. I have
that copy at my side.
All four of the formulas he's included use some sodium hydroxide
to achieve a high 11-12 ph. He mentions that the concentration of a
monbath must be 5 fold greater. Greater than what he does not say.
"The gamma value ... cannot be varied by change in dilution, time or
temperature ..."

Yep, high alkalinity to speed development. High concentration might be
why no one has previously made a monobath based on rapid fixer, too --
the fixer would be so fast not even HC-110 with extra alkali could
develop an image with usable film speed before the fixer dissolves it away.

Do you add ammonia over borax or bicarbonte for some reason? What
do you think might be your working solution ph?

I used ammonia because it was cheap and trivially available ($1.50 for a
gallon of household cleaner grade), compatible with HC-110 (most of the
chemicals in that developer are amido complexes or otherwise ammonia
based, and the developer is formulated to avoid dichroic fog that might
otherwise result from the ammonia content), and easy and safe to work
with. It would have been slightly more difficult, significantly more
expensive (for an experiment I wasn't certain would work), and
significantly more hazardous for handling and storage to use sodium
hydroxide, though it is just as readily available, sold as a drain
opener in grocery stores. For higher pH, carbonate would be the next
thing to try (bicarb isn't a lot more alkaline than ammonia); I already
have it, it's cheap and readily available, and it's easy to see when it
has neutralized the acid in the fixer because it'll stop foaming; I can
then add a selected additional amount (probably around 30-40 g/L) to
boost pH.

The working pH is probably similar to what HC-110 Dilution A would have
without the other additives (so probably about 8.5 to 9); the amount and
concentration of ammonia added is probably just about enough to offset
the acetic acid in the rapid fixer concentrate. I believe this to be
the case because development time seems to be similar to what I'd expect
with unmodified HC-110 A at that temperature; fixing time was adjusted
by concentration to ensure fixing didn't outpace development. I haven't
checked, but this would be easy to verify, by mixing those ingredients
with the water and testing with pH paper or a meter (which I don't
have), or including a drop of indicator stop bath concentrate and
watching for the color change.

BTW, Porter's may still stock in-cassette processors. Dan

Amazing. Of course, they can be used just as easily with conventional
three-bath process as with monobath; if you routinely shoot short rolls
and need to develop in the field, in-cassette processing means you don't
even need a dark bag to get your negatives.

--
I may be a scwewy wabbit, but I'm not going to Alcatwaz!
-- E. J. Fudd, 1954

Donald Qualls, aka The Silent Observer
Lathe Building Pages http://silent1.home.netcom.com/HomebuiltLathe.htm
Speedway 7x12 Lathe Pages http://silent1.home.netcom.com/my7x12.htm

Opinions expressed are my own -- take them for what they're worth
and don't expect them to be perfect.

John wrote:

On 12 Oct 2004 21:23:56 -0700, (Dan Quinn) wrote:

All four of the formulas he's included use some sodium hydroxide
to achieve a high 11-12 ph. He mentions that the concentration of a
monbath must be 5 fold greater. Greater than what he does not say.

Actually I think the pH was more like 13. Reminds me of the
developer in old Polaroid films. Caustic was a good word for
hydroxide. Once stuck a pH meter in some and permanently ionized the
probe beyond recovery.

Straight NaOH solution has a pH of 14, IIRC from college freshman
chemistry, 25+ years ago. There is some buffering by other components
of a monobath, however, so the final pH should be lower than that (and a
good thing; pH that high would probably just strip the emulsion off the
film base).

--
I may be a scwewy wabbit, but I'm not going to Alcatwaz!
-- E. J. Fudd, 1954

Donald Qualls, aka The Silent Observer
Lathe Building Pages http://silent1.home.netcom.com/HomebuiltLathe.htm
Speedway 7x12 Lathe Pages http://silent1.home.netcom.com/my7x12.htm

Opinions expressed are my own -- take them for what they're worth
and don't expect them to be perfect.