Olivinyl
Hello everyone,
I’ve still got two 5-litre bags of A300 fixer from the current production run here, just in case.
For film, the instructions state that you should prepare 4 litres from the powder intended for 5 litres, to make it stronger.
However, as I find the fixing times for film far too long (I’m used to Adofox 1+4), I’m wondering whether I can prepare the A300 in a more concentrated solution to shorten the fixing time a little. I was thinking of a 2.5-litre batch. That way, I’d also need fewer bottles of Aponorm...
Does this work in practice and chemically with A300?
Best regards, Oliver
piu58
That doesn't make sense. You need free thiosulphate ions. If the solution becomes too concentrated, the ions are forced into a bond with sodium.
michael-kielgmxnet
You can also store the fixer in an empty distilled water container, for example. Fixer isn’t sensitive to atmospheric oxygen, so you don’t need to use Aponorm bottles.
If you find the fixing times for film with the A300 too long, I would suggest you use it for RC paper (if you use that at all) and stick with Adofix for film.
A300 is rather unsuitable for baryta paper, due to the long fixing times and the consequently necessary long washing.
Olivinyl
@ Uwe:
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It’s good to know that the A300 doesn’t allow for that due to the chemical process.
In that case, I’ll use the recommended 4 litres of solution for films and PE paper and just have to be patient.
(as the social worker or nursery teacher would say: “stick it out!”)
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@ Michael:
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I use almost exclusively RC/PE paper, so no problem. I only keep A300 here in case I run out of fixer on a long, cold weekend and the shops are outrageously closed (although none of the shops here in SG have any fixer left on the shelves. Aponorm bottles are still plentiful.
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Best regards, Oliver
jochen53
Hello Oliver,
I assume that A 300 (Agfa 300, ORWO A 300, Calbe A 300) is a classic acidic fixer based on sodium thiosulphate. There are conflicting opinions suggesting it is an ammonium thiosulphate fixer, but if that were the case, it would be very misleading on the part of this supplier. And not everything you read on a website is necessarily correct.
Film fixers are always used at a slightly higher concentration than paper fixers. Old research findings have shown that the fixing rate initially increases with concentration (law of mass action), then reaches a maximum at around 40% Na<sub>2</sub>S<sub>2</sub>O<sub>3</sub> x 5 H<sub>2</sub>O, and then drops sharply again. This is partly due to the reduced swelling of the emulsion in such a high salt concentration. For economic reasons, it has become standard practice to remain within the range of 20–25% sodium thiosulphate pentahydrate, and that is where A 300 falls. Such a fixer can certainly also be used for films (1 sachet for 800 ml instead of 1000 ml), but even for TMax films, which are considered critical, the fixing time does not exceed 10 minutes. The fixing time can be easily determined using the well-known clarity test. For classic emulsions, use 2 times the clearing time; for TMax and Delta, use 3 times the clearing time. This method can also be used to check the fixing time in used fixers.
Sodium thiosulphate fixers attack the silver in the image (in negatives, particularly in the shadows) less rapidly than ammonium thiosulphate fixers if the exposure time is too long, and from what I gather from discussions about decomposition, sulphur precipitation, odour formation, etc., these issues seem to occur more frequently with rapid fixers than with classic ones.
Renate
Hello,
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A 300 used to be a classic fixer containing sodium thiosulphate. But that was a long time ago. All that remains of that are the old fixing times. The rule is: the clearing time multiplied by two equals the fixing time. And after that, almost all films are fully fixed within 3 minutes at the latest. I have been using A 300 for films and paper for several years now.
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Here in the shop, it is now also stated that A 300 is a fixer containing ammonium thiosulphate. My chemical analysis, which I carried out to be on the safe side, clearly shows that ammonium ions are present. A 300 has almost silently mutated into a classic rapid fixer. There’s no arguing with that. Why the times on the packets were never changed is a mystery to me. They no longer match up.
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Best regards
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Renate
jochen53
Hello Renate,
Thank you very much for your clarification; if you have detected ammonium, then that is probably correct. I don’t suppose anyone has dug up those ancient ammonium chloride/sodium thiosulphate recipes. Nevertheless, I personally don’t think it’s right to continue using the name that has been established for decades; however, it is even more unprofessional for a supplier not to adjust the fixing times.
StraDi
Hello,
I’d like to dig this old thread out of the archives for a specific reason, rather than start a new one on the same topic.
After my remaining Superfix went off following a long period of storage, I decided on the spot to use a ‘classic fixing salt’. For the sake of convenience, Adofix P seemed just the thing. However, once the order arrived, the following became apparent:
Adofix P is labelled as an ‘express fixer’ on the packet. This implies the use of ammonium thiosulphate. So it is not a ‘classic’ fixer. It seems that the posters above had already discovered this two years ago. But written a little smaller on the packet is ‘based on Orwo A300’!!
Dear friends: the Orwo A300 is a classic sodium thiosulphate fixer and therefore not an express fixer either! The A304 would be the closest equivalent, although it uses ammonium chloride in combination with sodium thiosulphate as an accelerator, rather than ammonium thiosulphate.
So even after two years, the labelling remains highly misleading! Either you state the fixing salt used on the packet, or you leave out such misleading terms as ‘express fixer’ and ‘based on Orwo A300’ altogether.
So I strongly suspect that this is an ammonium thiosulphate fixer that has absolutely nothing to do with the Orwo A30x formula. Conversely, it certainly wouldn’t be an ‘express fixer’.
cu ...
Dirk
StraDi
By the way... the sodium thiosulphate/ammonium chloride (or ammonia) rapid fixer recipes aren’t actually that ‘ancient’. Ammonium thiosulphate hasn’t been produced industrially in large quantities for all that long. What’s more, if the fixing process is allowed to go on for too long, ammonium thiosulphate attacks the silver in the image and is also difficult to wash out.
Many photographers have therefore opted out of using higher-concentration rapid fixers and prefer to use classic recipes. After all, there’s no need to process vast quantities of film or photos on an industrial scale, where every second counts. :)
See you...
Dirk
Renate
The mixture of sodium thiosulphate and ammonium chloride reacts in water to form ammonium thiosulphate and sodium chloride. This roundabout method was previously used only because it was not possible to buy enough pure ammonium thiosulphate of the required quality. In terms of function, the old and new recipes are identical.
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A300 does not keep for very long when dissolved. Sulphur precipitates out. Furthermore, sulphur dioxide is partially released as a vapour, which is very unpleasant and unhealthy. That is why I now work with Moersch fixer.
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Best regards
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Renate
StraDi
Hello,
Erm... yes... that’s clear enough (see above), but it doesn’t explain the misleading labels/designations on Adofix P. ‘Express fixer’ and A300 are simply mutually exclusive.
The ‘desulphurisation’ of (prepared/used) fixer can also be due to over-acidification of the fixer. Often, this is caused by a fixer that is too acidic (>3% acetic acid, for example) and the carry-over of this into the fixer.
The advantage of Adofix P is that the powder has a very long shelf life and can be stored for a long time. Unlike, for example, liquid fixer concentrates. Although you can sometimes get them ‘back into shape’ again.
cu ...
Dirk
Renate
The misleading labelling really annoyed me, as I’d originally bought the A300 to have a mild fixer. That was the selling point, after all. I’m currently using up the last pack and won’t be buying it again.
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I don’t use up 4 litres that quickly, as it goes off, and if I prepare it in single portions, the mixture can vary.
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Best regards
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Renate
HenningH
[...] Furthermore, if the fixing process is allowed to go on for too long, ammonium thiosulphate attacks the silver in the image and is also difficult to wash out.
What is the argument against removing the image from the fixer after a shorter period? By then, the silver in the image will not yet have been attacked, and so even rapid fixers are easy to wash out.
Renate
The problem is that the information on the packet was incorrect. In other words, people didn’t realise that the print could – or rather, had to – be removed after a short time. The fixing time was still stated as 10 minutes, even though it was actually a quick-fixing bath.
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Best regards
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Renate
HenningH
OK, that is obviously a problem.
But you seem to prefer soft fixation straps. Why?
