sanmich
Mentor
I am buying my Tetenal fix by the 5 liters, and it's the second or third time that at the end of the quantity, lots of particles are forming, like crystals in suspension.
After filtering, there is no visible particles, but the fix is kind of milky.
Can I use it?
should I damp it?
could I re-warm it to redissolve the particles?
Thanks
After filtering, there is no visible particles, but the fix is kind of milky.
Can I use it?
should I damp it?
could I re-warm it to redissolve the particles?
Thanks
Freakscene
Obscure member
It's amorphous sulfur. Using the fixer includes reactions that reduce thiosulfate to sulfate, which again reduces to sulfur. The fixer is still okay if the silver content is under 6 g/L, or roughly if the clearing time is less than twice the clearing time of fresh fixer. The sulfur can cause problems with marks on negs under some water conditions where it adheres better than it is removed by washing, but generally it gets washed off. If your negs are spotty, think about a different method, if they are fine, don't worry.
Marty
Marty
sevo
Fokutorendaburando
Often that is elementary sulfur that forms when the thiosulfate decomposes. You might want to figure out why it happens. In your case, "end of quantity" will be a good enough explanation, even more so if you are not using the stuff at regular rate (i.e. within weeks of opening), but have a half used canister about for months.
The severity of the issue depends on the formulation of the fixer. In some it is a sign of fatal damage, in others it does not affect the action as long as the solid is out of harm's way - in old hanger systems there often is a solid block of caked sulfur at the bottom of the fixer tank, to no harmful effect.
If it occurs in paper fixer used for temporary, non-critical purposes, you might filter or decant the bottle to get rid of the precipitate and test whether it still is fixing at the expected rate - small amounts will not visibly affect the prints, and archival issues will only strike after months or years.
For film use or exhibition grade prints you'd better dump the stuff - you positively don't want to have anything solid embed in a film emulsion, nor risk having a valuable print go blotchy, discolour or fade out.
The severity of the issue depends on the formulation of the fixer. In some it is a sign of fatal damage, in others it does not affect the action as long as the solid is out of harm's way - in old hanger systems there often is a solid block of caked sulfur at the bottom of the fixer tank, to no harmful effect.
If it occurs in paper fixer used for temporary, non-critical purposes, you might filter or decant the bottle to get rid of the precipitate and test whether it still is fixing at the expected rate - small amounts will not visibly affect the prints, and archival issues will only strike after months or years.
For film use or exhibition grade prints you'd better dump the stuff - you positively don't want to have anything solid embed in a film emulsion, nor risk having a valuable print go blotchy, discolour or fade out.
sanmich
Mentor
Thanks Marty and Sevo, but I wasn't clear: I am referring to the stock solution, concentrated and unused.
Freakscene
Obscure member
The reduction and sulfur precipitation can occur with age, irrespective of use. Thiosulfates are stable only in neutral or alkaline solutions, but not in acidic solutions, due to decomposition to sulfite and sulfur, the sulfite eventually being dehydrated to sulfur dioxide:
S2O32− (aq) + 2 H+ (aq) → SO2 (g) + S (s) + H2O
This all occurs spontaneously.
Marty
S2O32− (aq) + 2 H+ (aq) → SO2 (g) + S (s) + H2O
This all occurs spontaneously.
Marty
sevo
Fokutorendaburando
I am aware of that - it is less critical in working solutions where it is the natural process for some more old-fashioned types of fixer. Oxidation of stock is a bit more scary, as it will mean that the internal protection (usually sulfite) has been used up, so the stuff is positively past its best days and might suddenly turn entirely ineffective while you use it, so that you'll have to spend extra time testing whether it still is good at fairly frequent intervals. Fixer being relatively cheap I personally would not bother with it, as I only do quality work on silver any more - in the past I'd have used it up for proofs.
sanmich
Mentor
ibcrewin
Ah looky looky
I think it's awesome when you guys go all chemical on us. Takes me back to college!