OF-1 is Ole Fixer 1 bath.
OF-1 is Ole Fixer 1 bath.
OF-1 is:
600 ml water
220 g Sodium thiosulfate pentahydrate
30 g Sodium sulfite anhydrous
40 g ammonium chloride
20 ml Sodium metaborate 10% solution
OR 5 g Sodium bicarbonate
Water to 1 liter.
If it smells at all, use less alkali next time.
I mix this using four cups (the cup that's in the sodium thiosulfate sack) of one, a couple of spoons of this and that, and a goodly splash of the fourth - or a spoonful of the other. It's not critical. The amounts in the recipe were found by weighing my lumps, cups and splashes!
Which ingredient is the alkali ?
Can ordinary Sodium Thiosulfate be used in place of Sodium Thiosulfate Pentahydrate ?
If you have arrived at this formula in an informal manner, how do you know that it works, and doesn't give any bad side-effects ?
The last - metaborate or bicarbonate - is the alkali. It's there to make it better buffered againt pH changes.
If by "ordinary Sodium Thiosulfate" you mean the clear rice-grain crystals, that's exactly what the Pentahydrate is commonly known as. I sometimes use anhydrous, but that would only confuse matters.
I arrived at the furmula by sitting down with pencil and paper, and thinking hard for an hour or so. I wanted an easy-to-mix odorless alkaline-to-neutral rapid fixer without using ammonium thiosulfate (I had run out). Sometimes a university degree in chemistry comes in handy.
It works. I've used it for years, for both film and paper, including T-grain emulsions.
There's nothing in it that could give bad side-effects, although I generally recommend not using bicarbonate in combination with an acid stop bath.
Most Excellent - Thanks !!
Since you are a trained chemist, perhaps I could ask you: It seems that most of the Fixer formulas are based on thiosulfate of one kind or another - Sodium Thiosulfate and Ammonium Thiosulfate - with the remaining ingredients acting to stabilize or buffer.
Could something else be used, without sulfur ?
What is it about OF-1, which prevents the smell ? It also contains ammonium chloride, which I would guess, has a rather strong odor too.
The only alternative to thiosulfate is cyanide.
Thiosulfate is FAR safer!
The main odors from rapid fixers are sulfur dioxide from acidic fixers, and ammonia from alkaline fixers. In the middle there is an "odor-less" pH range - not totally odor-free, but with considerably less odor.
Regular stop bath makes me want some chips.Originally Posted by jnanian
And a chip butty!
I just recently got some Arista Premium odorless fixer from Freestyle. Just now I did what every chemistry teacher says not to, and took a good deep whiff, and it really has almost no smell.
Drew
https://www.flickr.com/photos/drew_saunders/
Very interesting discussion. I'd like to make my own fixer, but I need to keep it as simple as possible, because sourcing raw photo chemicals in Romania is very difficult at best. There are some points I'm not very sure about.
1. I believe that sodium thiosulfate does all the fixing job, right? So theoretically I could just use sodium thiosulfate and water, and nothing more, and still get a well working fixer. Is this correct? Will it work just as well as a commercial fixer?
2. If I use only sodium thiosulfate and water, the lifespan of the fixer will be very short. It's understandable. But how short? One week? One day? Less than one day? Will it at least work for the entire duration of a printing session (meaning five or six hours in an open tray)?
3. Sodium thiosulfate is slower than ammonium thiosulfate used in commercial rapid fixers, so I'd need longer fixing times. How long?
4. Is there any other preserver besides sodium sulfite that will work just as well? I'd like something widely available, something that can also be used for other purposes besides photography (so it can be easily found in supermarkets or drugstores), because sodium sulfite is almost impossible to find locally.
5. What does the ammonium chloride do? Is it an accelerator?
I'd expect the fixer to stink if you added ammonium compounds. How come it doesn't?
6. What's the purpose of using the alkali? OK, it prevents pH changes, but why is it so important to prevent pH changes? Won't the fixer work just as well regardless of whether it's acidic, alkaline, or neutral?
Thanks.
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