Hypo working dilution longevity

Here's a stupid question; how long does my hypo last? I process 8x10 in trays and I'd love to be able to bottle the hypo and save it for another round of developing. But there's sometimes a week (or more) between developing sessions.

Am I just being too cheap, or can I bottle the working dilution of hypo for use at a later time? Thanks!

Paul

That word "hypo" get a lot of misuse. "Hypo" is traditionally used as a contraction for sodium thiosulfate, a fixer. I have seen it used incorrectly in reference to hypo clearing agent, which is something altogether different. So which is it you mean, fixer or clearing agent?

Thanks for the clarification, Frank! I'm referring to the clearing agent. Right now I'm using TF4 as a fixer, and while it says that a hypo clearing agent isn't necessary, I use Kodak's hypo clearing agent to shorten wash times.

I've taken to reusing the fixer for at least two sessions, but I try not to let more than a week go by.

OK. Hypo clearing agent does not last very long as a working solution. The primary active ingredient is sodium sulfite, an aggressive oxygen scavenger. This property of sodium sulfite makes it extremely valuable as a preservative, and is why you see it in so many developer formulae. As it picks up oxygen, sodium sulfite converts to sodium sulfate which has no value as a clearing agent.

Instructions for Kodak's HCA (yet another contraction), indicate that the stock solution should be good for three months in completely full and well sealed bottles. Working solutions should be used once and discarded. There really is no need for this stuff if you already use an alkaline fixer. The long wash times usually recommended for fiber based papers assume an acid fix bath, which is much harder to wash out.

Interesting. Thanks for the detailed info! It confirms what I thought, i.e. that it's a one shot use. I'm trying to cut back on the water usage, as they tell me we're in the middle of a drought here in Northern CA. I'm wondering what the wash times should be for both 8x10 film (fp4+) and 8x10 papers. Right now I wash pretty vigorously for 30-40 minutes for the paper, and about 20 minutes for the film. If I could prevail upon you for one more answer, are those times adequate, excessive or not long enough with no HCA?

Thanks again!

Paul Cocklin said:

Interesting. Thanks for the detailed info! It confirms what I thought, i.e. that it's a one shot use. I'm trying to cut back on the water usage, as they tell me we're in the middle of a drought here in Northern CA. I'm wondering what the wash times should be for both 8x10 film (fp4+) and 8x10 papers. Right now I wash pretty vigorously for 30-40 minutes for the paper, and about 20 minutes for the film. If I could prevail upon you for one more answer, are those times adequate, excessive or not long enough with no HCA?

Thanks again!

Click to expand...

I use Hypo Clearing Agent (or PermaWash) for just a day and then re-mix.

If you use HCA before washing, then your times are adequate and perhaps could be shortened by as much as 50%. But whenever you are trying to push limits (e.g. minimizing wash times to conserve water) then you should test for residual fixer periodically.

Thanks Jerold. I think I'll pick one up and do a test to see just how long it takes an 8x10 paper to clear, then add 4 minutes.

Thanks to all for the help!

Paul Cocklin said:

Thanks Jerold. I think I'll pick one up and do a test to see just how long it takes an 8x10 paper to clear, then add 4 minutes.

Thanks to all for the help!

Click to expand...

Paul,

You might be confusing things, I'm not sure.

To determine paper fixing time:

1. Fully expose strips of paper to room light.
2. Put the strips directly into fixer
3. Fix the different strips for intervals of say 30, 45, 60, 75, 90 seconds (write the fixing time in pencil on the back of the strip before you start)
4. After fixing the strip, place it in developer for your usual development time

If you get any density on the strip, it was not fixed long enough. The first strip free of any density indicates the clearing time. Multiply that time by 2 to determine the fixing time.

Use the testing kits to test the paper that you believe is fully fixed to confirm that is true.

I rarely try to use fixer to exhaustion (false economy) but if you want to do so, use the appropriate test kit to test the fixer for exhaustion (precipitate).

Hypoclear or PermaWash is cheap so roughly monitor usage and replace during the day if you are doing volumes of work or else mix fresh for each printing session.

Thanks for the detailed breakdown, Jerold, but I meant I would test my washing times to see when the wash gets rid of the fixer entirely. I believe there's a bottle of testing liquid that you can use to test the paper after washing to see if there's still fixer in the paper.

But I think I will perform the test you've outlined for determining fixing time anyway. So far, I've just been doing it for 4 minutes with TF4, as that I believe is the recommendation on the bottle for paper fixing.

Thanks again!

Paul Cocklin said:

I'm trying to cut back on the water usage, as they tell me
we're in the middle of a drought here in Northern CA.

Right now I wash pretty vigorously for 30-40 minutes for
the paper, and about 20 minutes for the film.

Click to expand...

After a good rinse, film or paper, running water washes are
a Big waste of water. Further cleaning is due to the outward
diffusion of residual chemistry from the gelatin and paper and
the inward diffusion of water. The more dilute the chemistry
at start the sooner it is out and the less water needed.

Still water diffusion methods use the least amount of water.
Some porous non-woven sheeting material twixt sheets of
film or paper allows for untended soaking. My method for
still water washes uses two trays. Sheet materials are
transferred from one to the other tray.

Over running water methods, a Vast savings in water. Dan

Dan's method works. I am using a variation in it with a large tray with siphon and very low flow and a smaller tray for holding (prints) prior to washing. The holding tray gets changed a few times while I'm working my way up to 4 or 5 prints to wash.

And I have started adding a little scrap of the same paper, unexposed but fixed, at the end of the session so that I can use a residual hypo test after about 10 minutes in the piddle tray.

At the very least, invest in making or buying some residual hypo testing solution and you can get your wash time/volume down to its minimum.

Film is done similarly but in tanks instead of trays. Except for 8x10, that I do wash in a tray.

Paul Cocklin said:

So far, I've just been doing it for 4 minutes with TF4, as that I believe is the recommendation on the bottle for paper fixing.

Click to expand...

The fixing time on the bottle is one minute for fiber paper.