Sodium Thiosulfate "Plain Fixer"

rjas · Sep 15, 2006

I'm making FB prints and want to keep things simple, and I've been reading about the slightly-alkaline plain-fixer on Heylloyd.com. sodium thiosulfate anhydrous 160 grams, sodium sulfite anhydrous 30 - 60 grams, water to make 1L and used undiluted. 3-5 min fixing in 2x baths.

Few questions:

-What are the wash times for this fixer? Lloyd uses 90 minutes but I thought Alkaline fixes washed out super fast? (Tf-4 is something like 25 minutes without a hypoclear?) Is it because of the 3-5 min fixes x2?

I don't have a print washer so I'd be using soak and dump and 90 minutes is really long!

-Can I substitue Sodium Sulfite Pentahydrate (from the pool supply store) for the Sodium Sulfite Anhydrous? If so, how much pentahydrate to equal the anhydrous?

I would just order the chemicals to make TF-3, but ammonium thiosulfate in 60% solution is quite expensive to ship!

Thanks!

karavelov · Sep 15, 2006

rjas said:
I would just order the chemicals to make TF-3, but ammonium thiosulfate in 60% solution is quite expensive to ship!

You could make 60% solution of ammonium thiosulphate with 600gr Sodium thiosulphate and 400gr Ammonium chloride in a liter of water. Lot more cheaper!

Best regards
luben

rjas · Sep 15, 2006

karavelov said:
You could make 60% solution of ammonium thiosulphate with 600gr Sodium thiosulphate and 400gr Ammonium chloride in a liter of water. Lot more cheaper!

Best regards
luben

sodium thiosulfate anhydrous or pentahydrate? still confused about that one...

Ole · Sep 15, 2006

It's usually sodium thiosulfate that's pentahydrated, not sulfite.

For using sodium thiosulfate pentahydrate when anhydrous is called for, multiply the quantity by 1.57.

If it's sodium sulfite heptahydrate (there is no pentahydrate, it would be unstable) you're asking about, multiply by 2.0.

john_s · Sep 15, 2006

rjas said:
.....What are the wash times for this fixer? Lloyd uses 90 minutes but I thought Alkaline fixes washed out super fast?...........

Can I substitue Sodium Sulfite Pentahydrate (from the pool supply store) for the Sodium Sulfite Anhydrous? If so, how much pentahydrate to equal the anhydrous?

Thanks!

As Ole has already said, the hydrated form of sodium sulfite is the heptahydrate. The hydrated form of sodium thiosulfate is the pentahydrate. You can get some info, including the molecular weights, of chemicals from websites such as Sigma-Aldrich, Merck and many others. You would not want to buy their laboratory grade chemicals, but the info can be useful. The molecular weights can be regarded as "relative weights", for example, the Sigma website shows the M.W. for sodium thiosulfate anhydrous to be 158.11 and the pentahydrate to be 248.18.

If a formula calls for, say, 240g of the pentahydrate, and you have the anhydrous, you need 240x158/248=153g

The difference between the 248 and the 158 is 5 molecular weights of water (5x18=90)

The same sort of calculation can be done when finding equivalents of other anhydrous and hydrated salts.

AS far as Lloyd's washing times are concerned, he is very much a "belts and braces" kind of guy. You could get away with a bit less washing, especially if your fixer is not pushed to its limit of capacity.

srs5694 · Sep 15, 2006

rjas said:
I would just order the chemicals to make TF-3, but ammonium thiosulfate in 60% solution is quite expensive to ship!

Where are you located? I ask because most mail-order chemical suppliers who sell both chemicals sell ammonium thiosulfate for much less than sodium thiosulfate, at least when you compute the costs based on the quantities required for fixers. I've got a spreadsheet for computing costs of mix-it-yourself formulas, and as an example, the cost of 1 liter of working-strength plain fixer is $2.36, vs. $0.90 for the same amount of working-strength TF-3. These costs include shipping estimates to Rhode Island. Of course, if you live somewhere very remote, the shipping costs on the chemicals could conceivably reverse that. If you're interested, you can get my spreadsheet at http://www.rodsbooks.com/formulas.zip. That's a "raw" download link to a zip file that includes both the original OpenOffice.org spreadsheet and a Microsoft Excel export. You can adjust the costs on the first page to see how the final costs for the formulas change on subsequent pages.

Gerald Koch · Sep 15, 2006

rjas said:
-What are the wash times for this fixer? Lloyd uses 90 minutes but I thought Alkaline fixes washed out super fast? (Tf-4 is something like 25 minutes without a hypoclear?) Is it because of the 3-5 min fixes x2?
...

-Can I substitue Sodium Sulfite Pentahydrate (from the pool supply store) for the Sodium Sulfite Anhydrous? If so, how much pentahydrate to equal the anhydrous?

I would just order the chemicals to make TF-3, but ammonium thiosulfate in 60% solution is quite expensive to ship!

If you want a fixer that washes out rapidly then you have to use ammonium thiosulfate and not sodium thiosulfate. This is what TF-4 uses.

I think you are confusing sodium thiosulfate pentahydrate with sodium sulfite which does not have a pentahydrate but is usually sold as the anhydrous form.

If you don't want to purchase 60% ammonium thiosulfate to make a rapid fixer then just buy locally any available rapid fixer like Kodak Industrex Rapid Fixer and use it without the hardening solution.

rjas · Sep 15, 2006

Ole said:
It's usually sodium thiosulfate that's pentahydrated, not sulfite.

For using sodium thiosulfate pentahydrate when anhydrous is called for, multiply the quantity by 1.57.

If it's sodium sulfite heptahydrate (there is no pentahydrate, it would be unstable) you're asking about, multiply by 2.0.

Thanks.
It actually looks like ordering the Ammonium Thiosulfate 60% solution from photo formularly will be cheaper than from JDphotochem. I've been quoted $50.00 for 5L of Ammonium Thiosulfate 60% from JD! just over 3.7 litres of the same is $16.95 from PF!

Ole · Sep 15, 2006

1: Yes, it's "Rapid". Not quite as rapid as a "pure" ammonium thiosulfate fixer, but a lot more rapid than plain sodium thiosulfate.

2: Sometimes... I tend to use it full strength for film.

2&3: For paper I use a full strength first bath followed by a much diluted second bath / keeper tray (I don't have running water in my darkroom yet). The second bath is as low as 1:10 - just enough to have a little fixing activity left.

4: With film I treat it as a rapid fix with regards to wask times. It seems to work out.

Film clears in about 20 seconds, so with most papers a 90 second fix should be enough. That makes it very easy for me to keep track of since I have standardised on a 90 second development time for most papers.

gainer · Sep 15, 2006

Perhaps another consideration is that many if not most modern films have a considerable amount of silver iodide that is more difficult to fix out than the bromide or chloride, especially the the sodium thiosulfate is used. IIRC, adding ammonium chloride to a sodium ficer is not entirely the same as using ammonium thiosulfate from the start. PE is the resident expert here.

c6h6o3 · Sep 15, 2006

rjas said:
I'm making FB prints and want to keep things simple, and I've been reading about the slightly-alkaline plain-fixer on Heylloyd.com.

The correct recipe for a plain hypo fixer two solution bath:

1st Bath:
Dissolve 2 cups (16 oz. dry measure) sodium thiosulfate pentahydrate in 1/2 gallon of water at 90 degrees F. Add 25 grams of sodium metabisulfite. Let it cool to room temperature to use. Fix prints for 4 minutes.

2nd Bath:
Same as the first bath, but leave out the sodium metabisulfite. Fix prints for 4 minutes. Save this solution and add the sodium metabisulfite to it the next time you print. Use it as the first bath then.

Both sodium thiosulfate pentahydrate and sodium metabisulfite are available at reasonable cost from The Chemistry Store. The hypo comes in 20 # buckets or 50 # bags.

Kirk Keyes · Sep 15, 2006

Ole - you're a moderator - could you fix the title of this thread?

Kirk

Gerald Koch · Sep 15, 2006

c6h6o3 said:
The correct recipe for a plain hypo fixer two solution bath:

1st Bath:
Dissolve 2 cups (16 oz. dry measure) sodium thiosulfate pentahydrate in 1/2 gallon of water at 90 degrees F. Add 25 grams of sodium metabisulfite. Let it cool to room temperature to use. Fix prints for 4 minutes.

It's always safest to have any thiosulfate solution at or below room temperature before any acidic substance like sodium metabisulfite is added. This prevents the solution from sulfurizing.

Ole · Sep 15, 2006

Kirk Keyes said:
Ole - you're a moderator - could you fix the title of this thread?

Kirk

Umm... yes. Consider it an oversight. I must be going blind in my old age...

jim appleyard · Sep 15, 2006

It's not the age Ole, it's the mileage!

c6h6o3 · Sep 15, 2006

Gerald Koch said:
It's always safest to have any thiosulfate solution at or below room temperature before any acidic substance like sodium metabisulfite is added. This prevents the solution from sulfurizing.

Will that hold down on the odor? For my fixer doth yield an "exceding mightie and distresfull stink".

nworth · Sep 17, 2006

A simple sodium thiosulfate solution (240 g/l) works quite well and fairly rapidly as a fixer if you only use it for about 6 8X10 sheets per liter. It becomes exhausted rapidly. Although it will still convert the silver halide, it will not be able to free the silver from the emulsion after only a few sheets. That's where the sulfite comes in. It acts as a preservative to regenerate the active thiosulfate and to extend the life of the solution. Unfortunately, this only works well if the solution is slightly acid. I've been using F-34 (185ml ammonium thiosulfate, 10g sodium sulfite, 8.4g sodium metabisulfite) for several years with good results. The pH is 6.5, which is not so acid as to interfere with washing or staining but sufficient to provide full preservative action. A similar brew using sodium thiosulfate should be possible.

john_s · Sep 17, 2006

nworth said:
............... That's where the sulfite comes in. It acts as a preservative to regenerate the active thiosulfate and to extend the life of the solution. Unfortunately, this only works well if the solution is slightly acid...........

Does this mean that alkaline fixers don't last well? Or do they have another ingredient to preserve them?

I thought that acid facilitated the breakdown of thiosulphate (hence the smell of SO2), but I don't know the pH threshold of that reaction.

dancqu · Sep 17, 2006

Gerald Koch said:
If you want a fixer that washes out rapidly then you
have to use ammonium thiosulfate and not sodium
thiosulfate. This is what TF-4 uses.

In the end it is the thiosulfate which complexes with
the silver. The ammonium ion only acts as an intermediary.
In some manor you are suggesting that the ammonium ion
influences the diffusion rate of the thiosulfate.

TF-4's claim tor fast washing is based, at least primarily,
on it's rather high ph. Dan

nworth · Sep 19, 2006

john_s:

You are right about excessive acid decomposing thiosulfate. It also interferes with washing. Fixer must only be slightly acid (or neutral, or even a little bit alkaline - but I prefer just a little bit acid). The main function of the acid in fixers is to prevent stains and fog, both of which happen easily in alkaline solutions. The reactions in the fixer are numerous, complicated, and not very well documented in the easily available texts. But it seems to boil down to the fact that the lower silver thiosulfate complexes are not very soluble so sufficient thiosulfate must be available to make a preponderance of the higher complexes. Sulfite and particularly sulfurous acid act as a preservative in fixers, but too much acid causes numerous undesirable side reactions, including breakdown of free thiosulfate and reduction of the solubility for the silver complexes. I am very fuzzy about the exact mechanism of the preservative action - it just doesn't seem to be well documented anywhere that I have looked. One factor is simply to control acidity, keeping it reasonably low and preventing decomposition of the thiosulfate. But a number of other factors are at work as well, and they help keep the thiosulfate levels up. They seem to work best near neutrality down to very slighly acid. Equilibria are definitely a factor in fixing. There doesn't seem to be a pH threshold for any of the reactions, but the rates and effects are pH sensitive. The whole thing is to achieve a workable compromise.

Gerald Koch · Sep 19, 2006

dancqu said:
In the end it is the thiosulfate which complexes with
the silver. The ammonium ion only acts as an intermediary.
In some manor you are suggesting that the ammonium ion
influences the diffusion rate of the thiosulfate.

Sorry if my comment was unclear. You want to use a rapid fixer containing ammonium thiosulfate because with a FB paper it is contact with the fixer for a shorter period of time. This shorter time helps to prevent the various silver thiosulfate complexes from being absorbed in the paper fibers. Thus you can achieve archival stability in a shorter period.

Gerald Koch · Sep 19, 2006

c6h6o3 said:
Will that hold down on the odor? For my fixer doth yield an "exceding mightie and distresfull stink".

The less acid the fixer the less sulfur dioxide that is released. However with ammonium thiosulfate fixers the more alkaline the bath the more ammonia that is released.

Photo Engineer · Sep 19, 2006

Guys;

Sodium hypo fixes by forming a silver thiosulfate complex which diffuses out of the coating as a very large molecule of one silver and many thiosulfate ions. The optimum pH varies from 4.5 to about 10. As pH goes up, diffusion rate goes up due to the swell of the gelatin. At low pH hypo is less stable.

Ammonium hypo forms an ammonium + hypo complex with silver in which some of the hypo is replaced with ammonium ion which is smaller than the thiosulfate (hypo) ion. It therefore diffuses more rapidly. Complexation is also more rapid due to the superadditivity between ammonia and hypo.

The effective pH range for ammonium hypo is about the same as for sodium hypo, but above pH of about 8, the odor of ammonia becomes intolerable.

For color film, the optimum pH is about 6.5 - 6.8 due to the dyes.

That is a rough, non-technical explanation of fixation.

Leaving no fix behind is bad. Then there is no sulfur residue to protect the silver image. Leaving too much behind and you get silver and hypo in the material and you get stain and image degradation. The ideal is to leave just a tiny amount of hypo in the coating or use a material like Sistan to preserve the image. These preservatives must be used with caution, as they can cause image degradation themselves if used improperly.

For information on image stability, you may want to read the article by Ctein, or the journal article by Beveridge (Ilford). For information on fixing rate, try reading Mees or Mees and James, or Haist (V I).

Potassium ion can slow or nearly halt fixation. The reasons for this have never been properly explained. Therefore, the use of potassium in processing solutions is advised against unless you know what you are doing. (I suspect a diffusion problem, as the potassium ion is large relative to sodium and ammonium)

PE

john_s · Sep 19, 2006

Photo Engineer said:
..............Potassium ion can slow or nearly halt fixation. The reasons for this have never been properly explained. Therefore, the use of potassium in processing solutions is advised against unless you know what you are doing. (I suspect a diffusion problem, as the potassium ion is large relative to sodium and ammonium)
PE

Lots of us here are using potassium carbonate as part of Pyrocat-xx developers. I assume that the small concentration of K and a reasonable rinse after development would prevent such a problem.

Also, potassium carbonate and other potassium salts are in paper developers, especially concentrated liquid ones, because they are more soluble. The concentration of K in such a developer can be fairly high. Could this be more of a problem for correct fixing of paper?

Photo Engineer · Sep 19, 2006

john_s said:
Lots of us here are using potassium carbonate as part of Pyrocat-xx developers. I assume that the small concentration of K and a reasonable rinse after development would prevent such a problem.

Also, potassium carbonate and other potassium salts are in paper developers, especially concentrated liquid ones, because they are more soluble. The concentration of K in such a developer can be fairly high. Could this be more of a problem for correct fixing of paper?

I am aware of all of this.

It probably depends on the stop/wash between the developer and fixer, but if the potassium is in high enough concentration in the developer it can poison the fix or drastically slow it down.

Being aware of it, I have run some limited tests to show myself that it can be used in limited quantity in developers, but must be used with care.

PE

Sodium Thiosulfate "Plain Fixer"

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