[...]
WR> I can't understand why anyone would use a sodium fixer anymore.
WR> Of course, I have 10 pounds of the stuff gathering dust on my
WR> shelf. I suppose I should mix it up and use it.
WR> William Robb
I don't ewither (understand). But as the saying here goes, "custom is
an iron shirt" (if I translated it right).
But nobody should use sodium fixer (non-rapid) anymore! It's really
bad stuff for fixing:
1) with exhaustion, it's not consistent. The graph for exhaustion of
A sodium fixer B rapid fixer:
A: ____---==
..,--
B: ...--------===
So as you can see, the rapid fixer stays active for much more rolls,
then stops abruptly (so it's consistent) while the normal fixer looses
activity too soon.
2) Rapid fixer salts are better washable off the emulsion, unlike
sodium salts which when overfixed can form nearly UNWASHABLE chemical
complexes with the silver. Overfixing can be a big problem for
neg longevity with sodium fixers.
3) Easier - just think about mixing a powder and mixing a liquid.
4) price is not much a difference, unless you have large batches of it
left.
Most of all, the points 1 & 2 are a very strong recommendation of
rapid fixer. The graphs and data are from a chemistry book on
photgraphic chemistry, for anybody interested I can scan the graphs
and put them on my web.
A very simple (but not much scientific) test for presence of ammonium
salts in the washing water is to drop few drops of KMNO4 (the
metalic-pink crystals dilluted in water, just 2-3 crystals to get a
pink not saturated purple solution) to the washing water sample, if
the solution turns from pink to brown or the pink colour disappears
there are still quantities of ammonium salts. If it stays pink perhaps
just wash once more and you could be safe.
Also, use a hypo clearing agent. It really works and saves water a lot
(with USA being the most water-hungry contry on earth while ~2
*BILLIONS* people don't have enough drinkable water, I can't recommend
using a hypoclear enough... Think about it when you wash your car(s)
with drinkable water again)
HTH,
Frantisek
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