Expired Hypo Clear

[John Kasaian]

My jug has a notation I wrote "discard 1 June 2013"
Do you think it is still worth using? I'm all set up to print tonight and I'd hate to postpone it until I can get some more so I'll have to wash the fiber base prints longer....or go back and hypo clear the prints in day or two when I get more chemical.
What say you wise photographers?

[Mark Barendt]

I'd use it. I might run it through a fine strainer first.

[Mark Sampson]

HCA is a mixture of sodium sulfite and sodium bisulfite, IIRC. It shouldn't really 'expire'.

[Mark Barendt]

HCA is a mixture of sodium sulfite and sodium bisulfite, IIRC. It shouldn't really 'expire'.

The practical issue I've had is a precipitate, white crunchies, forming in the concentrate bottle during storage.

[C_Remington]

It becomes exhausted. It doesn't expired. You should always keep some hypo test around. It's so simple.

[John Kasaian]

Thanks guys! There are no crunchies, so maybe it's ok. Then again, I can pick up and mix some fresh stuff today.

[Robert Hall]

HCA working solution turns from sodium sulfite to sodium sulfate in about 4 hours in a tray. It oxidizes very quickly. Sodium sulfate has little effect of removing fix from prints or film.

From our friend Richard Knoppow...

The problem with sulfite is that it becomes sulfate when
it absorbs oxygen. Since one of the main purposes of sulfite
in developers and fixing baths is to absorb oxygen to
protect other chemicals it looses its effectiveness with
time and the protective properties are lost.
Sulfites also have a specific ion-exchange property for
thiosulfate. This is one of the main reasons its used as a
wash aid. Sulfate does no damage but is not as effective as
a wash aid and AFAIK, does not have the ion-exchange
property, which actively displaces thiosulfate and
thiosulfate-silver complexes.
The rate at which a sulfite solution becomes sulfate
from exposure to the air depends on its concentration: the
stronger it is the longer it will last. Of course, the
amount of exposure is also important, even a strong solution
will not last more than a few hours in an open tray while it
will have a life of several months in a closed bottle.
The soluability of dessicated sulfite is a couple of
hundred grams per liter (I've forgotten the exact amount) at
room temperature but its generally not found at
concentrations much above about 150 grams/per liter in
practical solutions to prevent crystalization at low
temperatures.
In short, sulfate does no harm but is not effective as
an oxygen absorber or preservative nor as a wash aid.

[tgtaylor]

That's good to know Robert. I mix stock solutions for film 250mm at time and it usually takes about 2 months before having to refill. The stock solution is mixed 10:1 to make a working solution.

Thomas