[pure-silver] Re: Non-acid rapid fixer - continued
- From: Lloyd Erlick <lloyd@xxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Fri, 19 Feb 2010 12:11:57 -0500
February 19, 2010, from Lloyd Erlick,
At 12:13 PM 2/18/2010 , Richard Knoppow wrote:
...
> A simple formula for a sodium thiosulfate fixer is as
>follows. For rapid fixer ammonium thiosulfate is substituted
>for the sodium thiosulfate in appropriate amount. Ammonium
>thiosulfate is usually sold as a liquid concentrate because
>the powdered version has a short shelf life.
>
>Simple non-acid, non-hardening fixing bath.
>
>Water 500.0 ml
>Sodium thiosulfate, crystalline 240.0 grams
>Sodium sulfite, desiccated 5.0 grams
>Water to make 1.0 liter
>
>The sulfite can be increased up to about 15 grams/liter to
>permit the use of an acid stop bath. The additional sulfite
>will prevent decomposition of the thiosulfate by the acid. A
>citric acid stop bath can be used with this fixer.
> However, any acid carried over into the fixer may
>result in some sulfur dioxide being emitted.
>
>--
>Richard Knoppow
>Los Angeles, CA, USA
>dickburk@xxxxxxxxxxxxx
>
>======================
I've been using the fixer formula above for many years. It's basically the
same as the one Ansel Adams published in the Appendix to The Print; he
called it plain fix. I use 160 grams per liter sodium thiosulfate
anhydrous, because that was the cheapest type available in hundred pound
bags when I went looking. I think the anhydrous form has supplanted the
crystalline because no one wants to fossil-fuel-transport that weighty
water of hydration all over the place.
I also found the presence of sulfur dioxide distressing. It seems as I age
I become more and more sensitive to stuff like this. I can no longer even
tolerate the fabric they use to make the labels in tee-shirts and jockey
shorts. If it touches my skin I feel burning and prickling and no other
business can fit in my mind until I deal with it. Sulfur dioxide and
hydrogen sulfide were the first gases to really get at me, but it has
broadened to the perfumes they put in dish and laundry detergents. There's
a product called Gain that just gases me out. I can't be in the room if
it's in the washing machine.
Anyway, the point of this diatribe - I found that a small amount of acid
finds its way all down through my process if I use an acid stop bath, no
matter how much I try to rinse the print after the stop. I tried using
citric acid stop, and it does smell much less than acetic acid, but it's
still an acid and down the line the formation of H2S and SO2 are still
possible.
To eliminate both these noxious gases (and by eliminate I mean render their
formation in the process impossible) simply eliminate acid from the
process. No acid stop and no acid fix - no noxious gases, and no stains
when the selenium toner is applied. (Acid in a fixer is there because of
the hardener, which works only in acid environment. Current production
materials either need no hardener, or have one built in. There is certainly
no need for the small capacity home darkroom worker to use hardener. Its
purpose is to protect the emulsions from damage. As hand-processing
workers, we should find it easy to handle materials carefully enough not to
scratch them. Anyway, I find it a lot easier to handle my materials
carefully than to allow sulfur dioxide in my darkroom.
Instead of an acid stop. I use four changes of plain tap water. Four might
be a bit excessive; three might do, or even two. The aim is to reduce the
amount of developer still in the paper, and four changes of rinse have
always removed enough that I can detect no staining in finished prints.
It's probably impossible to remove absolutely all developer by soaking it
out this way, but the same is true of an acid stop bath. A single acid stop
bath will soak out only a portion of the absorbed developer, and render it
inoperative due to acidity. A non-acid fix might allow development to
occur, so the developer has to go. I've found I much prefer just removing
the developer to the best of my ability and deleting the acidity.
A huge advantage to all this is that a selenium toning bath exposed to zero
acid over its service life performs much better and lasts longer. The
familiar black precipitate that occurs in selenium toner forms much, much
less rapidly when acid is absent. An occasional filtering of the selenium
toner through a coffee filter will keep it nearly water clear over its
entire life. Stains deposited on the tray are very reduced. I was never
able to make my selenium toner behave this nicely when I used any type of
acid anywhere in my process. It's important to me because I like to use my
selenium toner at a fairly high concentration (Kodak KRST diluted 1+5 with
distilled water) so it's expensive.
I realize all this blather makes it seem like cumbersome bother. But it is
actually easier, less effort, and cheaper. (Working single-tray helps
reduce bother too, but that's another pontification.) The plain fix above
is cheap and easy to mix in water at room temperature.
The lower capacity of the sodium thiosulfate fixer is an advantage, not a
drawback. One of the worst practices of the small-throughput darkroom
worker is keeping fixer around too long. The combination of partially used
fixer in a container and long periods of time is very bad for the fixer.
Having a high capacity fixer waiting around for us to "finish" it is
ridiculous. I prefer a low capacity fixer that is very cheap and very easy
to prepare (such as the formula above). I can exhaust it in one or two
sessions; sometimes after a session of making high-quality prints I
"finish" my fix in a later session making test prints and non-keeper work.
A liter of plain fix is so cheap I don't regret pitching it after one
session. I have pretty much abandoned storage of any liquid materials. I
just get out the powders and triple beam balance and make up nice fresh,
reliable, cheap solutions. (Developers too, but that's yet another
pontification.) It does not make things more awkward or time consuming. It
makes things quicker, easier, more reliable, and cheaper.
My formula for plain fixer is very close to the formula above that Richard
posted. I've marked off a couple of old yogurt containers so I can measure
my sodium thiosulfate with no scale (after the first time, that is). If
there is a little too much thiosulfate it's no problem, just a bit more
capacity that will likely be wasted. The serious error would be to use too
little, but that is easy to avoid. I use a table spoon to dole out my
sodium sulfite. I think it holds 20 or 25 grams, so I use a bit more
sulfite in my fix than the formula specifies.
And finally, my take on darkroom effluent. Discarding a fixer sounds very
bad for the environment, so discarding fixer more frequently sounds worse.
But - the fixer components are sodium thiosulfate and sodium sulfite.
Neither of these is bad for the environment, and both are used in other
industries in mountainous quantities. The bad thing we throw out with our
fixer is silver and silver compounds. It makes no difference how much fixer
we add to it, it's the silver that's the problem. This is determined by the
size and number of sheets of photo paper we use, and how much exposure the
sheets receive, not how much fixer we use. In fact, more fixer stored for
less time will generate less complex silver compounds, which is better for
throwing out than a high-capacity fixer kept for a long time.
I use plain fix for both fiber base prints and film (separate batches for
film and paper, though). I find I like to have three liters for each bath
(I use a two-bath fix), and I limit throughput to fifty rolls of film or
8x10 prints for my total of six liters.
I don't bother promoting my second fix to first position when the first one
becomes exhausted. I just pitch them both and make fresh ones. It's cheap
and easy.
regards,
--le
________________________________
Lloyd Erlick Portraits, Toronto.
website: www.heylloyd.com
telephone: 416-686-0326
email: portrait@xxxxxxxxxxxx
________________________________
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