TF4 Fixer- old but working?

Ordinarily I am of teh frame of mind that says "chemicals aren't that
much money, better safe than sorry, dump the old stuff"

I have a considerable amount of TF4 stock solution that is about 2 or 3
years old in a nearly full bottle. Formulary gives it a one year shelf
life, full.

I mixed some up and it cleared plus x film in about 30 seconds, and
some verichrome pan in about the same time.

I fixed a few rolls of VP for about 3 minutes. I have yet to do a
residual silver test, but will do this evening, time permitting.

My question is: What exactly happens when fixer gets past its "sell by"
date?
a) Does it only appear to fix the film while leaving a lot of
undissolved silver in the emulsion?
b) Does it still work, as long as it seems to work? (i.e. passing
the residual silver test)
c) Are times increased?
d) Would it make a good first fixer for a two bath process?
e) Are there any other reasons why it shouldn't be used?

I'm just curious, I've already ordered new fixer, but it seems a shame
to waste this if it is actually removing the undeveloped silver.

Its appearance, odor, and mixing behaviour are all normal.

Thanks

wrote

What exactly happens when fixer gets past its "sell by"
date?

IME, it deposits sulfur: thiosulfate + 02(?) - sodium sulfate + sulfur
(??? - something like that...).

I have never had it happen in glass bottles, but it happens in a
year or so in HD/LD PE plastic: Kodafix stock, Arista rapid stock,
working fix in Nalgene.

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
To reply, remove spaces: n o lindan at ix . netcom . com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

wrote in message
oups.com...
Ordinarily I am of teh frame of mind that says "chemicals
aren't that
much money, better safe than sorry, dump the old stuff"

I have a considerable amount of TF4 stock solution that is
about 2 or 3
years old in a nearly full bottle. Formulary gives it a
one year shelf
life, full.

I mixed some up and it cleared plus x film in about 30
seconds, and
some verichrome pan in about the same time.

I fixed a few rolls of VP for about 3 minutes. I have yet
to do a
residual silver test, but will do this evening, time
permitting.

My question is: What exactly happens when fixer gets past
its "sell by"
date?
a) Does it only appear to fix the film while leaving a
lot of
undissolved silver in the emulsion?
b) Does it still work, as long as it seems to work?
(i.e. passing
the residual silver test)
c) Are times increased?
d) Would it make a good first fixer for a two bath
process?
e) Are there any other reasons why it shouldn't be used?

I'm just curious, I've already ordered new fixer, but it
seems a shame
to waste this if it is actually removing the undeveloped
silver.

Its appearance, odor, and mixing behaviour are all normal.

Thanks


Its good. When fixer gets old it decomposes leaving a
deposit of elemental sulfur in the container and may develop
a strong sulfur dioxide odor. Because TF-4 is not acid it
probably lasts longer than acid fixer where the acid
decomposes the thiosulfate once the sulfite runs low.
Lack of complete fixing is a problem with partially
exhausted fixer. In order to completely tranform the unused
silver halide to a water soluble form there must be an
excess of free thiosulfate ions in the fixing bath. Fixer
will continue to clear film long after it stops completing
the fixing process. Do a Google search for posts to this
group by Michael Gudzinowicz for a complete explanation of
how the fixing process works. I think he posted it more than
once.


--
---
Richard Knoppow
Los Angeles, CA, USA

wrote:

I have a considerable amount of TF4 stock solution
that is about 2-3 years old in a nearly full bottle.

I mixed some up and it cleared plus x film
in about 30 seconds, ...


TF-4 stock solution; how concentrated is that and
do you adhere to any specific dilutions? Dan

Dan,
I'm not sure if this answers your question or not, but it comes as a
gallon which mixes down to 4 gallons. That is the dilution I adhere to.

Thanks Richard and Nicholas for your answers. Ferreting around in my
closet I found some ancient NH5 which resembled the insides of a
highway flare