Alkaline Fixer: is Ammonium Thiosulfate enough ?

[Ken Lee]

The formula for TF3 Alkaline Fixer at http://www.jackspcs.com/tf3.htm lists Ammonium Thiosulfate as the main ingredient, along with a bit of Sodium Sulfite, Sodium Metaborate, and water.

Are the Sodium Sulfite and Sodium Metaborate present to act as stabilizers or buffering agents - to preserve the life of stock solution ?

If so, could we use just the Ammonium Thiosulfate alone - diluted appropriately - as a one shot formula ?

[Nick_3536]

You can use plain hypo like this so I'm sure ammonium thiosulfate would be fine.

[Ken Lee]

Perhaps these other ingredients speed things up, slow things down, or perform some other action, like hardening, clearing, etc. ???

[Nick_3536]

pH adjustment.
Keeping qualities.

Hardening if it's a hardening fixer . TF-3 isn't

[Ken Lee]

So if we are supposed to dilute the stock solution by 1:4, that means we can make a liter of working solution directly, by merely adding 1/5 of a liter (or 200 ml) of Ammonium Thiosulfate to 4/5 of a liter (800 ml) of water. Then toss when done.

Sounds nice !

[iozone]

Ilford recommends 1 minute in Ilford Rapid Fixer 1:4 for archival processing. See here:

http://www.emsdiasum.com/microscopy/...ord/95065d.pdf



According to the MSDS for Ilford Rapid Fix it contains only ammonium thiosulphate and water. See here:

http://www.ilfordphoto.com/healthand...o=00110023.pdf



There is also a great dialog on a similar subject here:

http://photo.net/black-and-white-pho...g-forum/00EF2F

[Ken Lee]

Brilliant !

[IanG]

With no buffering from the Sulphite and Metaborate the capacity will be much lower, plus the sulphite helps tip the equilibrium balance with partially insoluble silver-thiosulphate complexes particularly as the fixer builds up silver in solution.

A fixer like Hypam is actually more effective because it has a better capacity than TF-3 or TF-4 and should cause no problems with staining developers either.

Should also say wash times with Hypam are similar to TF-3/TF-4

Ian

[Raffay]

On Jack's site under capacity it says that you can fix 20 8x10 sheets (i guess that would be 80 4x5, correct?) per litre. Is this the working solution they are talking about. If yes, then that would mean that from the stock of 1 litre we can make three such working solutions based on 1:4 ratio, so that will in total be good to process 240 4x5 sheets. Please some check my math and correct me if I am wrong.

Cheers
Raffay