How to tell when HCA stock has gone bad?

nihraguk · Oct 28, 2005

Hi everyone,

How does one tell when the HCA stock solution has gone bad? I mixed up a packet of HCA several months back (maybe 6 - 8 months I think) and stored the solution in several 1-litre plastic bottles, topped up to the brim. Some of the bottles began to "cave" in, but popped back into shape when I opened the cap and inadvertently let some air in.

I'm planning to start using FB paper, so I need to know if I can rely on my existing stock of HCA, or whether I would be better off buying a new packet and mixing it up.

BradS · Oct 28, 2005

Hypo clearing agent? I've never heard of it going bad just sitting in a bottle. It does get "exhausted" with use.

Terrance Hounsell · Oct 28, 2005

That is a good question an I don't really know the answer but here's what I do know.

I make my HCA from scratch, it only contains sulfite and a very small amount of metabisulfite. The main problem with HCA is oxidization which it does very readily. So I keep it in topped up in glass bottles. I didn't trust plastic for chemical storage as some of it breathes but recently I found a web site that tells how to determine if the plastic that you are using is any good:

http://silvergrain.org/Photo-Tech/plastic.html

Some people mix their HCA with their selenium toner in order to reduce a step and save time. However HCA oxidizes very quickly and selenium lasts much longer so you are in fact killing your selenium toner prematurely. Selenium toner is expensive.

In the end I don't really know how to tell when the HCA has oxidized. I don't see a colour change or other indicator. But sulfite is extremely cheap so I just toss the HCA and make a fresh batch whenever I'm in doubt.

Hope this helps.

Gerald Koch · Oct 28, 2005

HCA contains sodium sulfite which will oxidize to sodium sulfate when exposed to oxygen. This explains why a partially filled plastic bottle will "cave in" after a while. The oxygen is being removed from the air trapped in the bottle.

Certain plastics are permeable to oxygen and make poor storage containers for photochemical solutions. PETE (polyethylene terphthate) is OK, look for bottles with a "1" in the recycle triangle, usually water and soft drink bottles.

BTW, while sulfite ion is better at hastening the removal of hypo than sulfate, sulfate will still work. In fact, the original development of HCA was based on the observation that film processed aboard ship during WWII washed faster when sea water was used. The high concentration of salt in the water helped remove the hypo.

Agfa recommended a weak sodium carbonate solution as a hypo clearing agent.

nihraguk · Oct 29, 2005

Thanks guys, these were all very helpful and detailed replies.

jon koss · Oct 29, 2005

nihraguk said:
..how does one tell when the HCA stock solution has gone bad? I mixed up a packet of HCA several months back (maybe 6 - 8 months I think) and stored the solution in several 1-litre plastic bottles, topped up to the brim. Some of the bottles began to "cave" in, but popped back into shape when I opened the cap and inadvertently let some air in.

I'm planning to start using FB paper, so I need to know if I can rely on my existing stock of HCA, or whether I would be better off buying a new packet and mixing it up.

Assuming you are using Kodak HCA and typical PE bottles, definitely scrap it and start over. Polyethylene is a poor oxygen barrier. The HCA will have been attacked even if you have kept the bottles completely full and tightly sealed. The great yellow father recommends the following for its HCA: 3 months max shelf life for stock solution in a closed container, 24 hours max for working solution in a tray.

It will be a five minute / five dollar hassle to mix up a new batch. You will worry for the next ten years if you work with the old batch.

Just my perspective - not to be construed as constitutional law!

jk

Tom Hoskinson · Oct 29, 2005

jon koss said:
It will be a five minute / five dollar hassle to mix up a new batch...
jk

Or a lot less than $5.00 if you mix it from scratch. pH buffered versions of HCA contain Sodium Sulfite, Sodium Metabisulfite and water. A chelating agent - like Sodium Hexametaphospate - is optional if you have hard water.

See:

(there was a url link here which no longer exists)

nworth · Oct 29, 2005

The symptoms you describe sound like they were caused by atmospheric pressure changes or changes in the bottles themselves. They don't sound worrysome, but I wasn't there.

HCA generally doesn't get exhausted. It can get contaminated. You need to rinse things before you put them in HCA so the contaminents don't build up too much. Even then, eventually they will build up to where the HCA is not as effective as it should be. If HCA becomes acid, there is a chance that sulfur dioxide gas will be emitted from the solution. It smells terrible, but, in low concentrations, is not too hazardous. That might cause a slight swelling of a plastic bottle.

dancqu · Oct 31, 2005

nihraguk said:
... or whether I would be better off buying
a new packet and mixing it up.

You would be better off buying some sodium sulfite
and spooning up a serving of hca at time of use. That
sulfite alone will give all the hypo clearing possible. If you've
any sort of scale determine the average weight of a
measure by averaging several measures.

IIRC, you're local wine and beer home brew outlet will have
the sodium salt. Do not buy the potassium salt.

I only use hca with FB and use a 1% solution one shot. Dan

pnance · Jan 2, 2006

Tom, is your formula for a stock or a working solution. Thanks

pnance · Jan 2, 2006

Tom Hoskinson said:
Or a lot less than $5.00 if you mix it from scratch. pH buffered versions of HCA contain Sodium Sulfite, Sodium Metabisulfite and water. A chelating agent - like Sodium Hexametaphospate - is optional if you have hard water.

See:

(there was a url link here which no longer exists)

Is this formula for stock or working solution? Thanks

Tom Hoskinson · Jan 2, 2006

pnance said:
Tom, is your formula for a stock or a working solution. Thanks

It is a working solution - intended to be used undiluted. I personally use it as a one-shot.

However, since it is a buffered solution of sodium sulfite, it should have a reasonably long tray life.

dancqu · Jan 3, 2006

Terrance Hounsell said:
"That is a good question and I don't really know the answer but ..."

BUT AGFA DOES. Use sodium carbonate. Has Agfa ever
recommended otherwise. I have been using S. sulfite half
strength one-shot but the more I think of it a switch to
S. carbonate may be the rational thing to do.

Lloyd may comment. He is extremely careful in his processing
and has used the Agfa HCA for years. Dan

Lee Shively · Jan 4, 2006

"That sulfite alone will give all the hypo clearing possible."

Dan--are you saying sodium sulfite without the other chemicals mentioned is an effective hypo clearing agent? What measure per quart/liter for working solution do you recommend?

I'm just curious since I have a 25 pound tub of sodium sulfite on hand that I use with Rodinal developer. It's a simple matter to mix up a wash aid as needed if all I need do is dissolve the sulfite for one-shot use.

dancqu · Jan 4, 2006

Lee Shively said:
"That sulfite alone will give all the hypo clearing possible."

Dan--are you saying sodium sulfite without the other chemicals
mentioned is an effective hypo clearing agent? What measure
per quart/liter for working solution do you recommend?

I'm just curious since I have a 25 pound tub of sodium sulfite on
hand that I use with Rodinal developer. It's a simple matter to
mix up a wash aid as needed if all I need do is dissolve the
sulfite for one-shot use.

A 2% solution is the usual working strength. Using
your calibrated spoon measure and add that amount of
sodium sulfite to your solution; 1 liter? 20 grams.

The metabisulfite and the bisulfite are the same chemical
save for degree of hydration. The meta is minus H2O. That
it picks up as soon as water is added. Then it is the bisulfite.
The only reason it is included is to reduce the ph. Sodium
sulfite is a mild alkali and entirely useful as is. Perhaps
a technicality is the solutions longer life at lower ph
as suggested by Tom. IIRC, S. Anchell suggests
the lower ph for ferrotype purposes.

I would use it with confidence, short term. Follow the
usual guidelines. I use it half strength because I use
it one-shot with minimal solution volumes. Dan

How to tell when HCA stock has gone bad?

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