Who uses hypo clear?

Good morning everyone.

 

As per the title, who does/doesn't use hypo clear, and for what reason. When I learnt about film developing at college, we never used it, and I can't say I've ever had any problems that I know of.

 

Your thoughts please?

 

Many thanks, Rob

It's been included in most fixers for 30 years. Hypoclear is nothing more than sodium sulphite, used to absorb the extra unbound hypo. If it is in the fix, you are covered.

 

That said, it was important for prints and not so much film.

If you're talking about Perma Wash or Kodak Hypo Clearing Agent, these products reduce the necessary washing time substantially. You can wash negatives and prints successfully without them, but it takes a lot longer. I'm surprised a college darkroom wouldn't have supplied them since it can save a lot of water usage.

I used to use it on occasion, but as often not. None of my ancient images show much or any deterioration, so washing must have been good enough.

Conventional chemical based black & white films and prints display an image that is comprised of metallic silver imbedded in gelatin. Initially, rendering this image permanent was elusive. The problem was solved in 1837 using a mild sodium thiosulfate. In the middle of the last century, ammonium thiosulfate became available. Because this new “rapid fixer” (to render permanent) did the job in half the time: films 45 to 70 seconds, papers 2 to 7 minutes. Both did the same job, dissolving away un-exposed and un-developed silver salts.

 

Both have the same shortcoming; if these solutions remain imbedded in film and paper, in time they breakdown down to sulfur. Now sulfur attacks the silver based image. It tarnishes, turning the silver image blotchy brownish reddish that looks awful. To avoid this, the films and papers need copious washing in running water. No problem if you have the time and water is plentiful.

 

During World War II, the US Navy began the practice of conserving fresh water by first washing films and papers in seawater followed by a short freshwater rinse. It was then discovered that the seawater (2.6% salt) rinse could be quite short. In chemistry this is known as “salting out”.

 

Not long after this discovery, wash aids were on the market. Such solutions save water and time. These are mixes of several different salt solutions. Some are enhanced by adding peroxide.

 

Copious washing of films and papers are required. Without special treatment, it takes 30 minutes for films and 60 to 120 minutes, in running water, to gain archival status. Washing aids, sometimes called hypo clear (hypo is a nickname for thiosulfate) render films and papers archrival in just a few minutes.

I've read conflicting reports about whether film or prints need hypo clearing agent. What's the real story. Does 35mm film require HCA? Does resin coated paper need HCA?

 

Thanks.

I've read conflicting reports about whether film or prints need hypo clearing agent. What's the real story. Does 35mm film require HCA? Does resin coated paper need HCA?

 

Thanks.

@ Vincent Peri -- Films and papers wash nicely without the need for hypoclear or any other washing aid. These washing aids are to save water and time. If time and water are not precious, just use water.

I've read conflicting reports about whether film or prints need hypo clearing agent. What's the real story. Does 35mm film require HCA? Does resin coated paper need HCA?

 

Thanks.

 

Just read my first reply. It tells you why you probably will never have to.

Both films and papers use gelatin as the support for the silver salt goodies. After the developing and fixing process is complete, residual chemicals remain in this emulsion. Photo paper stock is generally wood pulp. The wood has a cell structure that traps and hold residual chemicals. Film washes clean in just a few minutes whereas paper needs more time. RC paper (resin coated) was supplied to the military in the 1940's to speed up the process of reconnaissance photos. The resin was a derivative of tree sap. Today, artificial resins made of polyester comprise the RC coat. This coat waterproofs the paper thus RC paper washing is much like washing film i.e. no cells to trap residual chemicals. Also the RC coat can be textured so the surface can be glossy, or have a sheen or pattern. However, the key to archrival images is through washing. Treating prints with sulfur or selenium etc. reacts with the metallic silver giving it a uniform brown or sepia tone. The warm tone is attractive and silver compound that results is nearly inert. A properly toned image will likely outlast the paper it is printed on.

Hypo clear is optional with film because it doesn't absorb much fixer to begin with, although I use hypo clear anyway (Perma Wash). It's virtually required for fiber-based prints because the large fixer molecules become entangled in the fiber paper base and are very difficult to wash out. Ilford used to publish a rapid-wash method for their fiber-based papers. The key is to minimize the fixing time to no more than 60 seconds in fresh ammonium thiosulfate rapid fixer mixed at film strength. Then immediately rinse in water, immerse in hypo clear for the recommended time, and transfer to a sink or tub of fresh water until you're done printing. Finally, wash all the prints for 15-30 minutes. My residual hypo tests showed that this method is more effective than two hours of washing without rapid fixing and hypo clear. Also, my residual silver tests showed that this method provides adequate fixing time if followed as directed.

With rapid fixer, and either film or RC paper, I haven't found much need for HC, though I do have an unmixed bag of it.

 

Even with fiber prints, rapid fixer still washes out pretty fast.

 

But I do have some fiber based paper, and if I start using it, I might use either HC or

Perma-Wash.

 

With non-rapid fixer, I would probably use it with film or RC paper.

With rapid fixer, and either film or RC paper, I haven't found much need for HC, though I do have an unmixed bag of it.

 

Even with fiber prints, rapid fixer still washes out pretty fast.

 

But I do have some fiber based paper, and if I start using it, I might use either HC or

Perma-Wash.

 

With non-rapid fixer, I would probably use it with film or RC paper.

Standard fix and rapid fix diffuse out of paper or film at the same rate. The task of a hypo clear is to reach archrival standards without the need for a prolonged wash in running water. My question is -- How do you know your washing technique results in films and papers that meet archrival standards? There are chemical tests. Let me add,. I won't be around to find out if you succeeded, takes about 50 to 60 years to find out if the sulfur is attacking the silver image.

Here's one for Alan-

 

I've found a few different recipes for hypo clear on the internet.

 

The usual formulas are 200g/L Sodium sulfite, and often with anywhere from 2g/L to 40g/L sodium bisulfite added. I've also found some that add sodium citrate at 4g/L and also sodium EDTA at 10g/L.

 

Any thoughts on all of this?(also, is there a target pH I should shoot for? If I use the citrate formula I'm likely going to be using citric acid solid and using sodium hydroxide to convert it to Na Citrate-from the titration curve for citric acid it looks like it should be fully deprotonated somewhere between pH 11 and 12, but this seems awfully high to me).

Turns out I had sodium citrate(or rather citric acid, trisodium salt as the bottle said) on the shelf, so I went ahead with the formula as above. I used 4g sodium bisulfite.

 

I didn't check the pH of it as I was too lazy to haul out a meter, calibrate it, and make sure the electrode was actually good-the pH is whatever mixing all of the above in DI water gives.

Standard fix and rapid fix diffuse out of paper or film at the same rate. The task of a hypo clear is to reach archrival standards without the need for a prolonged wash in running water. My question is -- How do you know your washing technique results in films and papers that meet archrival standards? There are chemical tests. Let me add,. I won't be around to find out if you succeeded, takes about 50 to 60 years to find out if the sulfur is attacking the silver image.

 

I do have negatives that are 50 years old, which is before I knew about rapid fixer.

 

I might have used HC from about 49 years ago.

 

I suspect I tend to over rinse my film and prints.

 

The recommended rinse times for rapid fixer seem to be less than for other

fixers.

As always a brilliant set of answers. Thank you all. Makes sense to me now as to why we were never introduced to it, the modern rapid fixers take care of it all. Cheers :)

Here's one for Alan-

 

I've found a few different recipes for hypo clear on the internet.

 

The usual formulas are 200g/L Sodium sulfite, and often with anywhere from 2g/L to 40g/L sodium bisulfite added. I've also found some that add sodium citrate at 4g/L and also sodium EDTA at 10g/L.

 

Any thoughts on all of this?(also, is there a target pH I should shoot for? If I use the citrate formula I'm likely going to be using citric acid solid and using sodium hydroxide to convert it to Na Citrate-from the titration curve for citric acid it looks like it should be fully deprotonated somewhere between pH 11 and 12, but this seems awfully high to me).

That is the recipe (200g/L) i have been using to make "Perma Wash"

But what is the purpose of the Sodium Bisulfite...some type of water treatment.?

Thank You

But what is the purpose of the Sodium Bisulfite...some type of water treatment.?

 

It's basically just a way to control the pH of the solution. If you were to mix just sodium sulfite, it will have some moderately high pH, meaning that it is on the alkaline side.

 

Now, if you were to lower the pH a bit by adding some acid, then some of the sulfite ion would become bisulfite ion. The result would be nearly identical to the case where you had initially mixed with a combination of sodium sulfite and sodium bisulfite.

 

In other words, I'm guessing that Kodak had some aim pH in mind, perhaps close to neutral (?), and they achieved this by specifying the formula as a combination of sodium sulfite and sodium bisulfite. Nothing more than this.

Alan thank you for the concise response as to how prints and their emusion deteriorate over time. I had always thought it was the remaining fix that had been the culprit, not the wood pulp. Just as I wished I began with the best of lenses while young, I overlooked the importance of hypo clearing. Even as recent as a few years ago I was washing my large prints with the sprinkler for a half hour. ! Hanging on the clothesline. But now I use hypo clearing agents for all my printing. Whites remain crisper white. I recently did a job where I re-soaked older (1940) fiber prints. One can simply feel the difference by touch.

Alan thank you for the concise response as to how prints and their emusion deteriorate over time. I had always thought it was the remaining fix that had been the culprit, not the wood pulp. Just as I wished I began with the best of lenses while young, I overlooked the importance of hypo clearing. Even as recent as a few years ago I was washing my large print s with the sprinkler for a half hour. ! Hanging on the clothesline. But now I use hypo clearing agents for all my printing. Whites remain crisper white. I recently did a job where I re-soaked older (1940) fiber prints. One can simply feel the difference by touch.

@chris_autio --- It's not the wood pulp, it's the breakdown of the fixer to sulfur. The cell structure of the wood pulp based paper that traps the fixer making it hard to purge residual chemicals. Film emulsion is based on gelatin is a more open structure so clearing the residual chemicals is faster for film.

It's been included in most fixers for 30 years. Hypoclear is nothing more than sodium sulphite, used to absorb the extra unbound hypo. If it is in the fix, you are covered.

 

That said, it was important for prints and not so much film.

It's been included in most fixers for 30 years. Hypoclear is nothing more than sodium sulphite, used to absorb the extra unbound hypo. If it is in the fix, you are covered.

 

That said, it was important for prints and not so much film.

@ peterbcarter -- Sodium Sulfite is the preservative. Fixer's break down to form colloidal sulfur. Sodium Sulfite will react with the colloidal sulfur to form sodium thiosulfate, the ingredient of a standard fix bath. Sodium sulfite is also used as the preservative in a developer solutions but its action in the fixer solution is quire different.

It's basically just a way to control the pH of the solution. If you were to mix just sodium sulfite, it will have some moderately high pH, meaning that it is on the alkaline side.

 

Now, if you were to lower the pH a bit by adding some acid, then some of the sulfite ion would become bisulfite ion. The result would be nearly identical to the case where you had initially mixed with a combination of sodium sulfite and sodium bisulfite.

 

In other words, I'm guessing that Kodak had some aim pH in mind, perhaps close to neutral (?), and they achieved this by specifying the formula as a combination of sodium sulfite and sodium bisulfite. Nothing more than this.

 

Even closer if you use sulphurous acid.

 

The bisulfite is convenient in being a solid acid, where some are liquids as concentrates, even at 100%.

We used it regularly at the newspaper I worked. It greatly shortens wash time for prints. It prevents staining from under washed prints. Mine have remained stain free for over 50 years. Later, we switched from fiber based to resin based paper, which could be washed in about 15 minutes. We never used it for film.

I might remember some movies about newspaper stories, where they were in a rush to get the story out.

 

Fix barely long enough, a quick rinse in water, dry with a hair dryer, and out to press.

 

For pictures that are news one day, and trash the next, there is no need for archival processing.

(Maybe on the negatives, where you can always make more prints later. But you can go back

and properly do it after the article is sent to press.)

Didn't Ilford determine that 5 soaks in fresh water, can't remember the time, did the trick? Most of the water used in a running bath likely doesn't do anything and is wasted.