Mixing your own hypo clearing agent ("washing aid")

I mix my own HCA rather than buy Kodak's overpriced version. Mine is

simply sodium sulfite.

 

Just wanted to check up on my formula and measuring technique, which

may be useful for others wishing to do the same. Since I don't have a

scale, I measure by volume using the high-tech quantity known as

"tablespoons".

 

I mix liters at a time of concentrate (which gets diluted 1:9, or 1+9

if you prefer, to the working solution), dissolved in hot water. The

concentrate consists of 200g of sodium sulfite per liter. Since,

according to Pat Gainer on this forum, one tbsp. of sodium sulfite is

25g, 8 tbsp. of sodium sulfite per liter should be just the ticket. Right?

 

One question about sodium sulfite: I have a hard time understanding

why this chemical would require a preservative. How can a simple salt

go bad? It can't oxidize, can it? Shouldn't it have an indefinite

shelf life? Seems to me the only thin that could happen is that the

salt could precipitate out of solution.

 

By the way, for those concerned about the safety of chemicals used in

the darkroom, I discovered that if you Google on "sodium sulfite"

you're likely to get as many food-related hits as photo-related ones.

Sodium sulfite is commonly used as a preservative and for drying

foods. So it's literally safe enough to ingest. (Don't know how it

tastes, though: have to try it one of these days!)

Old Navy Photo books mentioned using seawater; then a way less amount of fresh water is used at the very end; to remove the salt. This is used where fresh water is at a premium; and salt water free; ie on a ship at sea.

Not an answer, but another question. Since the word about using sea water for the majority of the film washing process is pretty well known, I was wondering if a solution of sodium chloride, ie. table salt and water might be just as effective as a wash aid. Any comments, experiences, etc., welcome.

Are you asking why the sulfite in HCA? If so I don't think it's in to perserve anything. It helps "liberate" the chemicals created during fixing. Making them easier to wash out. At least that's my understanding.

 

On the safety feature you can drown in water but trying going without it. Just because something is safe doesn't mean it isn't dangerous.

No, I'm asking why it (HCA itself, or basically sodium sulfite) <i>needs</i> a preservative. I don't see how sodium sulfite, a simple inorganic salt, could go "bad" by itself.

<p>It would also be interesting to get an answer to the other question about whether common table salt would work as HCA. After all, as we all know (from being constantly reminded by Kelly Flanigan if for no other reason), the way HCA was "discovered" in the first place was through the use of seawater to wash prints on board ships during WWII, where it was found that it assisted with the removal of hypo. And that was just common NaCl.

By the way, my curiosity got the better of me today and I took a taste of sodium sulfite. I can say with certainty that you don't want to use it in your salt shaker. It has a kind of nutty taste, actually, plus that underlying "photographic" smell that seems to emanate from most of the chemicals we use.

I would advise against taste testing most photo chemistry. Definitely not a good idea with pyrogallol, possibly metol and others.

My understanding (which may be wrong) is that NaCl in the wash

helps to draw out any chemicals, hence improves speed of wash.

HCA style compounds on the other hand as well as drawing out

the chemicals, actually assist with breaking long chains of

fixer molecules into smaller pieces which can be removed more

easily.

 

Chemicals can have a finite life. This is due to reaction

with things like oxygen from the air, contaminants in the water

etc. Think about it. Sodium Sulphite is used as a preservative

in developers. To do so it must react with say oxygen more readily

than the developing agent, thus preventing the developing agent

from being degraded i.e. preserving it. Again this is my interpretation of what I have read, it may be incorrect.

Which formula are you looking at? The one I'm looking at includes Sodium bisulfite to lower the pH and Sodium Sulfite which is the actual active part of the formula. Does the formula you're looking at include a perservite?

No, to keep things simple, my "formula" <i>is</i> sodium sulfite. You don't really need any of that other stuff (added for buffering and preventing taking the gloss off paper). I was just wondering about those other formulae which include preservatives.

<p>So, previous poster: are you saying that sodium sulfite oxidizes? That's a surprise to me, but then, not being anything of a chemist, a lot of this stuff is surprising to me.

The matrix of the gelatin opens up in alkaline conditions so a

teaspoon of soda (sodium carbonate) in two litres of water will

improve the effectiveness of the wash.

So you add sodium carbonate to sodium sulfite?

No, I just use plain sodium carbonate in water, but you could mix the two although I doubt that there would be any advantage. I just use soda because its cheap and easily obtainable.

a long time ago i read about mixing your own developer with metol.

they suggested putting in a pinch of sodium sulfite first , to keep the developer from oxidizing and darkening.

if my old memory is correct, this means the chemical prevents oxidation.

What conceration of sodium carbonate are you using Chris?

 

Are you sure it has the same effect as Kodak washing aid?

 

What's your washing procedure? times?

Peter,

 

I use a level teaspoon of sodium carbonate (anhydrous) in 2 litres of water. This makes the water just a little more alkaline and thus opens up the gelatin, hence making it easier to wash out the fixer. I put about 1 cm of the solution into a dish and just rock it to and fro for about a minute, then I repeat. Then I wash in plain water for about 2 more minutes. I tried this after reading an article in a recent issue of 'Ag'.

Peter, I searched out that article last night. It was written by Michael Maunder and appeared in 'Ag', issue no. 31. He noted that acid wash water was up to 10 times less efficient at removing fixer than alkaline water. I live in a hard water area and it is just very slightly alkaline, but I tried soda to increase the alkalinity. Maunder suggested 'a pinch' of sodium carbonate. I have use a level teaspoon per 2 litres, but I think that maybe 1/2 or even 1/4 teaspoon would be sufficient.

A plastic 35mm film cannister of sodium sulfite is ~50g, fwiw.

Thanks; I got the volume measurement figured out, based on 25 g/tbsp. I have a 2 oz. measure, which holds 2 tbsp., therefore 50g. And yes, it's just about the size of a 35mm canister, so that's a useful bit of info.

<b> A word of caution!</b><br><p>

 

I came across this old thread. <b><u>Do not</u></b> taste either sodium sulfite or sodium metabisulfite. While these are commonly used food preservatives, some people are allergic to sulfites. Breathlessness, coughing, and asphyxiation are all entirely possible outcomes. I speak from personal experience. I narrowly avoided the last, but spent a very unpleasant interlude in the emergency room, hooked up to oxygen after ingesting a bottle of heavily sulfited (chaeap) champagne, many years ago. At the time, the allergy was little known.