Fixer Test

[ASA1000]

I understand the Residual Hypo test, but if I leave a tray of FRESH fixer exposed to air for some period of time, when I'm ready to use it is there a test to see if it's still any good?
(and yes I understand it should be covered and not be left exposed to air... but what if?)
thanks in advance!

[Doremus Scudder]

You use a residual silver test to test adequacy of fixation, not the residual hypo test. The residual hypo test is to test washing.

For testing residual silver, you need the ST-1 test or the selenium toner test. I like the latter, since I have selenium toner around all the time. To make a test solution from Kodak Rapid Selenium Toner, just dilute it 1+9 (or stronger, even 1+1 works just the same). I imagine that other manufacturers' selenium toners would work similarly. It lasts indefinitely. The ST-1 test solution has a shorter shelf life.

Kodak® Residual Silver Test Solution ST-1
Distilled Water . . . . . . . . . . . . . . . . 125 ml
Sodium Sulfide (anhydrous) . . . . . . . 2 g
(This solution keeps for 3 months in a small tightly-sealed bottle.)
To use, dilute 1 part of the above stock solution with 9 parts distilled water. This working solution keeps less than a week.

Whichever test solution you use, the procedure is the same: Squeegee your print or film and place one drop of the working solution on an unexposed border area (the idea is to use an area that has all the silver halides fixed away, so you need a completely unexposed area). Let the drop sit for 3 minutes and then blot with a clean cloth or tissue. Any discoloration other than a barely-visible cream tint indicates that your print or film still contains silver halides that require further fixing to remove.

This means your fixer is not doing its job. Either it's overused (out of capacity) or it has oxidized and lost activity due to age. The same test works for both scenarios.

That said, it is better to keep track of how long the fixer has been out, exposed to air and use Ilford's shelf-life recommendations from their tech pub here: https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://assets.website-files.com/5ba2689b2e7121210bfa9af3/5c0ecc53472033a2b1b17efb_tech%2520specs%2520ilford%2520rapid%2520fixer.pdf&ved=2ahUKEwii4pbltYaHAxXAGzQIHUXGCXwQFnoECB8QAQ&usg=AOvVaw1UtnsEwdWtEiUcSXh1Asni

I highly recommend that you read it thoroughly; there's a wealth of information there. So, from the document (this is about Ilford Rapid Fixer, but applies to most similar products):


WORKING SOLUTION LIFE
...
Unreplenished ILFORD RAPID FIXER working strength solutions should last for up to:-
6 months in full tightly capped bottles
2 months in a tank or dish/tray with a floating lid
1 month in a half full tightly capped bottle.
7 days in an open dish/tray.

Hope that answers your questions.

Doremus

[ASA1000]

Thanks, your answers are always informative and I'll definitely read the link, but I was wondering if there were some 'droplets' or test strips I could use to test the fixer before making any prints. That last tidbit about Rapid Fix and '7 days in an open tray' .... would that be the same timeframe for the F24 metabisulfite paper fix I use?
thx X2

PS I just looked at your website. I see you are with Joette in Santa Fe. I was picture editor for the paper there and later had my office in LaFonda. I used to talk to Joette and Nick all the time! Small World!

[Pieter]

I will dip a corner of an pice of scrap (like 35mm leader) unexposed, undeveloped film in the fixer for 1 minute. If it comes out clear, the fixer is good.

[jk0592]

In ST-1, are we really meaning sodium sulfide or sodium sulfite ?

[LabRat]

I will dip a corner of an pice of scrap (like 35mm leader) unexposed, undeveloped film in the fixer for 1 minute. If it comes out clear, the fixer is good.

To expand on what Pieter said, the film clip test is standard for rapid fix solutions...

When fixer is fresh (with proper dilution) it should clear an unexposed/undeveloped film clip in about a minute, and your fixing time in process is double that...

After multiple use, clip film clearing time might double or triple, and in pro labs, they would use that to determine that the fixer needed to be replaced then... There are many other factors of byproducts build-up residual silver etc, but doubling of fixing time was the result of these factors, and a good indicator...

Rapid fixer tends to operate in the open air for a long time (like in deep tanks or vats), so storage just keeps solution cleaner and less fumes in the work area...

Steve K

[Duolab123]

I remember in the 70's Edwal made a hypo check solution. 1 drop, in the tray, a white precipitate would form, if it quickly disappeared fix was good. If the ppt was slow to disappear or persisted it was time for fresh fixer. I've never trusted any solution that has been left over 8 hours in an open tray. If fixer is oxidized it will smell and have sulfur precipitate out.

[jnantz]

I remember in the 70's Edwal made a hypo check solution. 1 drop, in the tray, a white precipitate would form, if it quickly disappeared fix was good. If the ppt was slow to disappear or persisted it was time for fresh fixer. I've never trusted any solution that has been left over 8 hours in an open tray. If fixer is oxidized it will smell and have sulfur precipitate out.

hi duolab123

I used to use hypo check too but if it's speed fixer I was told by local photo chemists it will give a false reading for exhaustion. now I only do the clip test ( and recommend it along with a 2 bath fixer). film leader is cheap. and usually found on my floor . :)

[Doremus Scudder]

Thanks, your answers are always informative and I'll definitely read the link, but I was wondering if there were some 'droplets' or test strips I could use to test the fixer before making any prints. That last tidbit about Rapid Fix and '7 days in an open tray' .... would that be the same timeframe for the F24 metabisulfite paper fix I use?
thx X2

PS I just looked at your website. I see you are with Joette in Santa Fe. I was picture editor for the paper there and later had my office in LaFonda. I used to talk to Joette and Nick all the time! Small World!

ASA1000,

I was at Photogenesis for years, but, sadly, Joette passed away unexpectedly some months ago. Her husband, Nicholas Trofimuk, has closed the gallery and returned everyone's prints. It's a great loss to the photo scene in SF. Thought you might like to know.

Best,

Doremus

[Doremus Scudder]

In ST-1, are we really meaning sodium sulfide or sodium sulfite ?

Definitely sulfide. It basically tones the residual silver in the paper/film to make it visible (just like a sulfide toner :) ).

Doremus

[Doremus Scudder]

I will dip a corner of an piece of scrap (like 35mm leader) unexposed, undeveloped film in the fixer for 1 minute. If it comes out clear, the fixer is good.


I remember in the 70's Edwal made a hypo check solution. 1 drop, in the tray, a white precipitate would form, if it quickly disappeared fix was good. If the ppt was slow to disappear or persisted it was time for fresh fixer. I've never trusted any solution that has been left over 8 hours in an open tray. If fixer is oxidized it will smell and have sulfur precipitate out.

You can certainly use the film clearing-time test to see if unused fixer that has been stored or exposed to air for a long time is still good. You, of course, need a clearing time for that particular film in fresh fixer. If it clears in the same time, then no problem. However, if it takes longer, even if it is not near the 2x-clearing-time limit, it means that the fixer has begun to oxidize and "sulfur-out." This means the oxygen-scavenging sulfite in the fixer has been depleted and that the fixer is on its way out rather quickly. Plus, there may be flakes or precipitate in the solution (more important for film than paper). It would be wise to mix new if this is the case. Since you're using a "conventional" fix and not a rapid fix, the clearing time in fresh fix for film will, naturally, be longer than one minute or less, which is normal for rapid fixers.

Note that fixing FB paper to archival standards requires much less dissolved silver (i.e., fixation by-products) in the fixer than either fixing film or RC paper, which can stand a lot more dissolved silver in the fix. For this reason, the Edwal Hypo-Check is not really sensitive enough to use for print fixers for FB prints; it doesn't give an indication that the fixer is exhausted till dissolved silver levels are too high for FB prints. For film fixer, it's likely alright, but the clearing-time test is better.

Best,

Doremus

[jk0592]

Thanks!