Sodium Thiosulfate Fixer Formula

[asaphoto]

I am trying to formulate a simple fixer using bulk sodium thiosulfate. A friend of mine uses.

1lb of sodium thiosulfate
2 tbs sodium bisulfiate
1 tesp sudium sulfite

to make about half a gallon of fixer.

What I want to know is are the additives required or can you use the sodium thiosulfate straight? Also what do the additives in the fixer? I see some people use citric acid. What dose that do?

 

[Petzi]

Citric acid is also used as a separate stop bath, instead of acetic acid. Citric acid is preferred when the odor of acetic acid is unwanted.

The purpose is, to neutralize the alkaline developer and stop development.

 

[jim appleyard]

Sure you can use Sod. Thio (plain hypo) straight, but it won't last long. That's where the Sod. Sulfite comes in as a preservative.

 

[Brook]

The bisulfite acts as a buffer so the acid stop bath doesnt sulfurize the hypo . rendering it useless. If your using a two bath fix, the second can be plain hypo.
I personally never found citric acid stops any less offensive than acetic acid.

 

[juan]

There's also TF-2, here.

What are you fixing? Film, paper? For paper, lots of photographers use plain sodium thiosulfate and throw it away at the end of a session.
juan

 

[matt miller]

lots of photographers use plain sodium thiosulfate and throw it away at the end of a session

That's what I do.

 

[laverdure]

If you use a plain water stop bath (or two), your fix won't need any buffering. Plain hypo's great. With or without preservatives. Take a look at this for more:

http://heylloyd.com/technicl/plain.htm

 

[Tom Hoskinson]

http://www.michaelandpaula.com/mp/Azo_Formulas.html

 

[dancqu]

The bisulfite acts as a buffer so the acid stop bath
doesnt sulfurize the hypo . rendering it useless.

Bisulfite is it self acidic. The OP's formula will likely
yield a slightly acidic fixer due to the bisulfite. Sulfite
is decidedly alkaline. Dan

 

[Wayne]

For paper, lots of photographers use plain sodium thiosulfate and throw it away at the end of a session.
juan

You dont even need to weight it. Just toss in about 1/4 hypo by volume IIRC.


Wayne

 

[laverdure]

You dont even need to weight it. Just toss in about 1/4 hypo by volume IIRC.

I think this is true of the pentahydrate, but not the anhydrous. Which is to say, the crystals, not the fine grains. Penta needs a higher temperature to dissolve (~115f?) however than the anhydrous (~80f.)

 

[Wayne]

Yes, penta is what I was referring to. I've never used anything else so I forget that some people do.


Wayne

 

[dancqu]

What are you fixing? Film, paper? For paper, lots of
photographers use plain sodium thiosulfate and throw
it away at the end of a session. juan

Works for film as well. If interested in trying it use
16 grams of the anhydrous or 25 grams of the penta
in whatever volume of water needed; 10 + minutes
with intermittent agitation. A 120 roll in my tank
receives 500ml. One roll, one shot.

I've not tested with the T or D films. Dan

 

[dancqu]

Use it Straight!

I am trying to formulate a simple fixer using bulk sodium thiosulfate.

What I want to know is are the additives required or can you use
thesodium thiosulfate straight? Also what do the additives in the
fixer? I see some people use citric acid. What dose that do?

I use it straight, very dilute, one-shot. I've done a lot of
testing over the years and find it works well. My latest tests
have brought down the concentration to 1% anhydrous when
processing FB paper. Fix times are under 4 minutes and the
single very dilute one-shot fixer yields archival results. On
an 8x10 basis volume is 300ml.

For film the concentration runs 3.2%, anhydrous. A 120 roll is
fixed in a 500ml solution volume.

The chemicals listed other than the sodium thiosulfate act
both as preservatives and ph modifiers. Citric acid will lower
the ph.

Any off the shelf fixer can be used very dilute one-shot.
Very pleasant surprise. I had had for years drilled into my
head that some certain dilutions were necessary. Now not
so. Needs no stop or rinse. Archival results with 1 disposable
fix and A tray needed for processing. Quite a shrugging of
convention wouldn't you say? Then again, alternative
processes, alternative methods.

Great for cramped quarters. Similar to the rotary method
save for A tray rather than A tube. Dan

 

[Ryuji]

Dan,

There is no archival standard set for a fixer of the concentration ranges you mentioned. The ISO standard for archival processing specifies the kind of fixers, the maximum allowable silver content in the fixer bath and the residual thiosulfate level. Your processing is not well tested to claim "archival."

Weak fixers may appear to clear the material in a few minutes, but the complete fixation is much slower than clearing time. I understand you emphasize one-shot use, but even then, I would be very leery to recommend such practice.

Plus, you are not really saving chemicals. Most film strength fixers contain about 120-160g/L of thiosulfate in anhydrous form, and a liter of fixer can process 20 rolls. That's 6-8g of thiosulfate per roll. Your method requires 16g per roll, and extra fixing time, and unknown archival quality.

 

[Anscojohn]

Did you all notice he said bisulfAte? That's a hardener.

 

[dancqu]

Did you all notice he said bisulfAte?
That's a hardener.

Any usual bisulfate is a very acid salt;
eg, sodium bisulfate. It can be used as
a substitute for sulfuric acid. It is not
a hardener. Dan

 

[dancqu]

[QUOTES=Ryuji;461647]

"There is no archival standard set for a fixer of the
concentration ranges you mentioned."

And just what would that standard for fixer be?
The only "standard" I'm aware of is the amount of
silver per unit volume. Are there perhaps some
duration of time for fixation standards?

"The ISO standard for archival processing specifies
the kind of fixers,"

Not the Brand?
That leaves us Home Brew sorts a little room.

"the maximum allowable silver content in the fixer bath"

I do not know the ISO standard but am aware of the Haist
and Ilford limits

"and the residual thiosulfate level."

A post wash matter which concerns the end product.

"Your processing is not well tested to claim "archival.""

Not by ISO prescribed procedures, if that be meant.
Then again whose processing is? Dan

 

[Ryuji]

The ISO does not specify fixer brand. But all the numbers and procedures described in 18917 and 18901 assume standard fixers (thiosulfate concentration of about 0.8-1.2M). Both sodium thiosulfate and ammonium thiosulfate fixers are specified.

"the maximum allowable silver content in the fixer bath"

I do not know the ISO standard but am aware of the Haist
and Ilford limits

The number in Haist's book was later revised and raised very much higher than his number. The ISO standard specifies about 100x greater number than what Haist gave, but the exact number depends on the fixer type and material.

When something is described to be archival, the material and processing must be very well tested to back up the claim, or the users are very ill-advised. This is the reason why ISO standard exists and used as standard test for archivality.

 

[dancqu]

[QUOTES=Ryuji;462065]
"The number in Haist's book was later revised and
raised very much higher. The ISO standard specifies
about 100x greater number than what Haist gave, but
the exact number depends on the fixer type and material."

My guideline must then be Very conservative. Haist's 0.2
grams silver per liter and Ilford's 0.5 grams silver per liter
are the figures upon which I claim an unofficial archival
fixing for paper. Purely an arithmetic conclusion as to
the state of the FIXER.

"When something is described to be archival, the material
and processing must be very well tested to back up the
claim, or the users are very ill-advised. This is the
reason why ISO standard exists and used as
standard test for archivality."

Most darkroom workers are not aware of the ISO standard,
the Standard Solutions, Reagents, Standards for testing
results and the approved devices used in evaluating
results, etc, etc.

Importantly, through out this discussion I've found nothing
to indicate that a very dilute fixer cannot produce archival
results. It is no fault of mine that the ISO standard is so
narrowly constructed that it cannot verify archival
processing outside a very narrow range of fixer
concentrations.

Some one of those ISO committees would do us all a favor
by establishing some few specific procedures we at home
or at the shop might use to measure the correctness of
our processing. Dan

 

[Ryuji]

My guideline must then be Very conservative. Haist's 0.2
grams silver per liter and Ilford's 0.5 grams silver per liter
are the figures upon which I claim an unofficial archival
fixing for paper. Purely an arithmetic conclusion as to
the state of the FIXER.

A standard fixer A with 150g/L of ammonium thiosulfate, and a dilute fixer B that is 30g/L behave differently in terms of clearing time, time they take to complete fixation, tolerance for maximum silver concentration, etc. It's not even proportional. You can't take the standard established for fixer A and apply it to B to claim B is archival.

Most darkroom workers are not aware of the ISO standard,
the Standard Solutions, Reagents, Standards for testing
results and the approved devices used in evaluating
results, etc, etc.

Sure, but most of those people are buying their chemicals or mixing according to well tested formula. People who devise a new method, especially if they advocate the method, should be very familiar with standards, testing methods and existing scientific knowledge. These are very different kinds of people.

Importantly, through out this discussion I've found nothing
to indicate that a very dilute fixer cannot produce archival
results. It is no fault of mine that the ISO standard is so
narrowly constructed that it cannot verify archival
processing outside a very narrow range of fixer
concentrations.

I agree there is no direct evidence to fail archivality and I never phrased my words that way. But there are strong cautions. Anyone introducing a vastly different fixer has to consider every potential issue and design the formula to solve problems and confirm the formula is actually free of any of those anticipated problems. It is a burden on the person who advocates new things. Frankly, in this particular case, this burden is not worth doing. If your technique had a very clear advantage I would encourage you to go through the trouble to establish the superiority, but in reality, as I showed in my previous posts, your method does not save chemicals, save time or minimize waste.

 

[dancqu]

[QUOTES=Ryuji;461647]
"Weak fixers may appear to clear the material in a few minutes,
but the complete fixation is much slower than clearing time.
I understand you emphasize one-shot use, but even then,
I would be very leery to recommend such practice."

Well that is or was a problem with very dilute fixer; clearing
time. In particular, fixers so dilute as I use have no - twice
the clearing time in fresh - check for exhaustion. The first
roll through is the last.To make matters worse the FT-1
test is not usable as the amount of complexed silver in
the used fix is too little to make a determination.

To test I backed way off on the chemistry and put
unexposed unprocessed rolls through ever increasing
strengths of fixer; worst case for the fixer what with all
the silver salts present. Mottled very pink to start then
a loss of the mottled appearance and pale pink and
finely crystal clear and no hue. A little stronger
still for some margin and that for worse case.

I'm going to be doing some test with Acros. The NBS
method, now a reinstated post, should be possible. With
the stain stabilized I can test with my densitometer. Now
the test for residual siver. The ST-1 may do; a silver for
sulfur, HT-2, a sulfur for silver, ST-1. The NBS again.?

"Plus, you are not really saving chemicals."

May be, may be not, in practice. Each fresh fix need not
be at worse case strength. Likely the 20 rolls mentioned
has been arrived at by averaging. I know Ilford does
that with paper capacities.

Mine is not a one-size-fits-all method. I use all chemistry
one-shot very dilute. I store no used chemistry and
single tray processing is made easy. Dan

 

[Ryuji]

Ok, this is a better thread!

In my experience, Delta 400 is probably the hardest film to fix. Acros is not that slow to fix in comparison.

"Likely the 20 rolls mentioned has been arrived at by averaging. I know Ilford does that with paper capacities."

Ok, check the simple math. 80 square inch is about 0.05 square meter. Most modern paper have about 0.1g per sheet. Modern films should contain less than 0.25g, more like 0.2g or less of silver per 80 sqi.

Assuming none of them got developed (worst case for fixer):

You multiply 0.25g/roll and 20 roll/liter, then you get 5g/L. Good for standard fixer.

You multiply 0.1g/sheet and 50-100 sheets/liter, then 5-10g/L. Still good for rapid fixer.

I think the processing capacities published by Ilford and silvergrain would not exceed the ISO standard by much even if you look at strictly the worst possible case where you get not a single image until the solution exhausts. In realistic case, about half of the silver gets dissolved into fix on average.

I must emphasize that fixer processing capacity is not something you want to play a risky game , whether the reason is to save pennies or being a lazy ass.

In reality, unless you are ultra careful and use squeegee, you lose much of the solution before you go through 100 sheets of paper. If not, you are diluting the fixer with stop bath carryover. This is another reason it's best to start with strong, standard fixer concentration.

 

[dancqu]

... you lose much of the solution before you go through
100 sheets of paper. If not, you are diluting the fixer with
stop bath carryover. This is another reason it's best to start
with strong, standard fixer concentration.

You've not the picture. I don't lose any solution. One sheet
goes through the very dilute developer and then the developer
is dumped. A measure of very dilute fixer is then poured in the
tray, no stop. After about four minutes of my special agitation
the fixer is dumped.

The amount of silver in the volume of solution used is that
from ONE sheet of paper. The current Volume of all chemistry
used for an 8x10 is 300ml. At 0.1 gram per 8x10 that is 0.33
grams per liter of fixer. BTW, I use an average for all papers
of 0.08 grams per 0.05 per sq. meter. I recognize that
each paper needs testing for it's minimum chemistry
requirements.

Mine is not mainstream processing but is similar to rotary
tube processing employing one-shot chemistry. Dan

 

[Ryuji]

Dan,

I feel that you are trying to convince me something but without addressing the concerns I described above. Needless to say it's not that you need to convince me to do your process. I'm merely saying that your method is not comparable to archival processing standards and you might want to be careful in making your archival argument.

For example, there is no simple way to compare whether 0.3g silver per liter of your dilute fix is better or worse than 5g silver per liter of standard rapid fixer. Existing published data show rapid decline of fixing rate below about 0.8M of thiosulfate (exact number depends on emulsion and temperature), adn so there is a valid concern whether the risk of insufficient fixation due to dilute fixer is acceptable.

Dilution by carryover fluid is not an uncommon problem with people who use "economy" or "paper" dilution set on some fixer products.