hypo check: what am i looking for?

[jbl]

I've generally been using film strip tests to test if my fixer is still any good, but the other day I figured I'd try some hypo check. I've developed about 14 rolls of 35mm in my current 1-liter batch of Kodakfix. When I drop the hypo check in, the drops turn white, but then dissipates. My recollection from chemistry class is that a precipitate would stay solid and sink to the bottom and this definitely doesn't happen.

Does this mean my fixer is still good?

-jbl

 

[eddie]

If it turns white, the fixer is shot. In fresh fixer you won't see the hypo-check at all. As the fixer ages, you'll see a "clear" precipitate.

 

[brucemuir]

I dump it just before it turns white to be safe.

After awhile you can judge the hypo-check and how thick it gets in relation to silver retention in the fix.

I've heard time and again a leader test is a much better test.

 

[2F/2F]

The drops sez your fixer is bad. If any milky cloud forms, for however long, it is bad. It always forms and then dissipates.

However, several people here whose technical knowledge I usually trust have repeatedly said that the drops are not a solid way of determining whether or not fixer is good, and that when a leader clears in twice the initial clearing time, the fixer is done.

I am surprised the fixer is gone after only 14 rolls. Usually I get at least 20. Have your negs been on the thin side? That would exhaust the fixer more quickly, the same way thicker negs would exhaust a developer more quickly.

 

[Tori Nelson]

Does anyone know if hypo-check goes bad?

 

[removed account4]

as 2F suggests the leader test often times is a great way to check ...

if i recall correctly ...
the bottle of hypo check has instructions that suggest you remove 1oz of fixer
from the tray and put the drops in that. stir it and if it vanishes it is still good,
if it stays cloudy it is bad ... drops in a tray of fix do not indicate well ...

 

[Shadowtracker]

I always use the leader test because I'm too cheap to buy drops... but really, its simple to just save the leaders of films and test them now and then, keep track of it for a while, and then you generally know when you should be close to pitching the stuff out. I still test, and more frequently, as I get closer to my 'approximate' time that I think I should be throwing it out. I remember using drops in the past, but haven't used them in recent years because I never knew if the drops could go bad or not. I suspect they don't go bad, but a leader that takes too long to clear is easy to see and isn't disputed.

 

[holmburgers]

Just for the sake of having a "comprehensive" thread, would someone please describe the leader test. It seems like a much more practical/easy way to test fixer.

 

[Shadowtracker]

When you cut the leader off a 35mm film to spool it before development; save it, hang it in your hypo (fixer) and wait. Mark how much time it takes for the film to 'clear'. When using fixer on your developed film, double the amount of time it took for the leader to clear. Lets say that it takes 2.5 minutes for the leader to clear. So you fix your film for 5 minutes. When it takes 10 minutes for the film to be fixed (or 5 minutes using the leader test), then pitch the fixer and make a new batch.

That's the leader test.

 

[fschifano]

The "leader test" is probably the best way to tell if your fixer is exhausted or nearly so, but you need to apply some controls for it to be a reliable indicator of the fixer's condition. The type of film used for the test affects the clearing time. Temperature also affects the result, but to a lesser degree. In order to make the test valid, you need to use the same type of film for the test each time. Temperature should be close, but needn't be controlled to tightly. A few degrees one way or the other doesn't make that much difference. Example: Foma films will clear in a fresh rapid fixer in 30 to 40 seconds. In the same bath, a clip of TMax film might take upwards of two minutes. Clearly if you did one test using Foma film and followed it up a few days later with a test using a clip of TMY, you'd be sitting there scratching your head trying to figure out what's going on. Then how do you know when the film is completely cleared? Well, unless you have a reference, looks can be deceiving. Take 1 drop of the fixer in question and apply it to the test film. Let it sit for 30 seconds, then immerse the chip into the fixer. When you can no longer see any difference between where you placed the initial drop and the rest of the film, it is clear.

 

[Doremus Scudder]

To expand somewhat (or perhaps more than somewhat) on Shadowtracker's post:

The clip test (we large format guys don't have "leaders," so we just sacrifice a sheet of film and clip strips from it to test the fix) is best done as follows:

1. Put a drop of fixer on the center of the strip and wait 30 seconds.
2. Immerse the strip in fixer and start timing. The area with the drop will clear first and give you a good visual reference. Observe the strip under good illumination till you can see no difference between the drop area and the rest of the film.
3. Note the time. This is the "clearing time."

Most advice I see recommends fixing the film for a minimum of two times the clearing time. However, in either "The Darkroom Cookbook" or "The Film Developing Cookbook," Anchell and Troop recommend three times clearing time, especially for modern films (e.g., T-Max) due to the silver iodide used in the emulsion. I fix for a minimum of three times the clearing time.

Repeat the clip test before every batch and use the appropriate time by multiplying the new clearing time by the appropriate factor (3x in my case).

Discard the fixer when the clearing time is twice that of the clearing time in fresh fixer. I toss the fix when the clearing time is even close to 2x. Fixer is cheap, better to err on the side of caution.

Caveat: Test the same film you will be developing; different films have different fixing times. Also, different films exhaust the fixer at different rates, so your best results will be if you use the same film. If you have to mix films, do tests with both and base capacity on the first film to reach the 2x point.


A few words on fixing methods:

I have standardized now on either dilute, "paper-strength" fix (e.g., a rapid fixer 1+9) or two-bath fixing. This decision was made after reading a lot about maximum permanence and fixer exhaustion.

Using dilute fixer results in longer fixing times and fewer films for a given solution volume before the 2x-clearing-time limit is reached, but keeps by-products from fixing from building up higher concentrations in the solution. I use this method when I just have a few films to process.

Two-bath fixing (exactly like the method used for fiber-base prints) is what I use when I have a large number of films. It saves fixer and ensures adequate fixing. The clearing time in fresh fix is divided between two equal-size baths. Capacity is determined by doing clip tests on the first bath only. When bath 1 is exhausted (i.e., has reached the 2x-clearing-time point), it is discarded and the second bath becomes the new bath one. A fresh second bath is mixed. This can be repeated for up to seven cycles (which I rarely do; one or two cycles is a lot of film for two 500ml baths).

As you can see, there is no fixed capacity number; fixer is tossed when exhausted. The clip test is probably the best easily-available test to determine fixer exhaustion. IMHO you can forget the drops and just use the clip test. The test (and your results) will be better.

Hope this helps,

Doremus Scudder
www.DoremusScudder.com

 

[holmburgers]

Awesome replies, very thorough and sounds like a great method to test it. I'll be doing it soon!

 

[Shadowtracker]

Doremus, I am just getting into LF, so thanks much for the tips on how to do that with LF film. And thanks to you all for other clarifications. I assume time/temp standards so often forget to include those when talking with others.

 

[jbl]

14 rolls

My negs haven't been thin, certainly not in this batch. Mostly, I've been developing well exposed TriX at 320 in HC-110 (1+49). The negs have looked really good. Could it be something else?

-jbl

I am surprised the fixer is gone after only 14 rolls. Usually I get at least 20. Have your negs been on the thin side? That would exhaust the fixer more quickly, the same way thicker negs would exhaust a developer more quickly.

 

[clayne]

I've found that when using 2-bath fixing, a hypo-check test will indicate a saturated 1st bath much earlier than what rated capacity for 2-bath fixing indicates is possible. Basically, if one uses hypo-check as authoritative with a 2-bath setup, they're throwing away the 1st bath much too early. Can any of the fixer experts comment?

 

[MattKing]

Let me see if I have this right .....

As I understand it, fixer reaches capacity in two different ways.

One way is that it's chemical capacity becomes exhausted, due to use. The "clearing test" measures this capacity.

The other way is that the fixer becomes over-saturated with silver (a byproduct of the fixing process). The "hypo check" measures this effect.

Arguably, you could have fixer that continues to have chemical capacity, but is otherwise over-saturated. Also, you could have fixer that still has room to absorb more silver, but has used up it's chemical capacity.

As I understand it, with most photographic films and papers, the chemical capacity test is more important, because the fixer loses that capacity faster than it acquires silver. For old style lithographic materials, the reverse is probably true.

Please correct me if my understanding is wrong.

 

[2F/2F]

I've found that when using 2-bath fixing, a hypo-check test will indicate a saturated 1st bath much earlier than what rated capacity for 2-bath fixing indicates is possible. Basically, if one uses hypo-check as authoritative with a 2-bath setup, they're throwing away the 1st bath much too early. Can any of the fixer experts comment?

Is this with a fresh first bath, or with a first bath that had previously been a second bath?

 

[RalphLambrecht]

I agree with Doremus' proposal(s). Preferably, use a one-shot two-bath fixing method, and you can forget all fixing problems. However, two-bath fixing is wasteful if you are using non-rotational, single-film processing, in which case the clip test is the better option. Don't overuse fixer at the risk of losing your images!

 

[2F/2F]

What exactly is "non-rotational, single-film processing"? Processing one roll of film in an inversion tank?

What about two? Or four?

 

[RalphLambrecht]

What exactly is "non-rotational, single-film processing"? Processing one roll of film in an inversion tank?...

Yes, sorry for the wordy description.

 

[2F/2F]

Yes, sorry for the wordy description.

Not complaining about wordiness. Just wondering if you really meant what you said that specifically. I meant to ask if you would also keep the fixer after a two- or four-roll batch, or if you very specifically meant just one single roll.

 

[RalphLambrecht]

Not complaining about wordiness. I just meant to ask if you would keep the fixer after a two-or-four-roll batch, or if you very specifically meant just one single roll.

I use fresh developer and fixer for every batch of processing. Whatever fits into the tank at one time, gets fresh chemistry for consistency.

 

[2F/2F]

Ralph,

I thought you mentioned that if you want to use a two-bath process, it is wasteful to use the fixer one shot in hand inversion tanks, so the leader test was a good way to go. This is to what my question referred.

 

[RalphLambrecht]

Ralph,

I thought you mentioned that if you want to use a two-bath process, it is wasteful to use the fixer one shot in hand inversion tanks, so the leader test was a good way to go. This is to what my question referred.

Yes!

 

[dancqu]

Dissolves

When I drop the hypo check in, the drops turn white, but
then dissipates. My recollection from chemistry class is that
a precipitate would stay solid and sink to the bottom and this
definitely doesn't happen. Does this mean my fixer is still good?

As the drop/drops first enter the solution there is a momentary
local concentration of iodide. The iodide ion is common to the
potassium iodide entered into the solution and to insoluble
silver iodide. So, if a certain minimum of either are
present a precipitate will form.

The thiosulfates, sodium or ammonium, dissolve silver iodide.
If there is enough free thiosulfate present and, after a time
and/or stirring, the silver iodide will dissolve.

The problem with FT-1 type tests is there lack of quantification.
The test is actually a titration with no quantities specified. Very
un-scientific. The closest I've found to scientific is Kodak's
FT-1 test. And it is questionable. Dan