Reliable Fixer Test

[Doc W]

I just finished a batch of prints but I am suspicious about the fixer. I didn't notice the colour because of the colour of the tray, but it is a little yellow. It still clears a piece of film but it just doesn't look ... healthy... so I am going to dump it and refix those prints. So I have two questions:

1) refixing - is it as simple as it sound, i.e., just re-do the fixing stage?

2) what is a reliable fixer test? I use a non-hardening fixer for prints (Ilford Rapid Fixer) and a hardening fixer for film (Kodafix).

 

[Rudeofus]

There are different kinds of yellow, some harmless, and some definitely not harmless:

1. There could be a yellow precipitate or milkyness in your fixer. That's Sulfur which precipitates out when all the Sulfite is used up (usually by aerial Oxygen) and pH drops too low. If that's the case, your fixer is dead, do not process further film or paper in it.
2. You could be seeing carryover stop bath (do you use indicator stop bath?). This would show up as clear yellow color, sort of the same as very dilute stop bath. This is completely harmless, until it's too much that either your fixer is too dilute or it becomes too acidic and enters stage 1 of this list.
3. You could be seeing carryover developer, which is quite likely if you don't use a stop bath. This would likely happen if you don't use a stop bath or water rinse between developer and fixer, and shows up as yellow/brown color which should be clear. It is mostly harmless, as long as you don't turn on the regular room light until fixation is complete.

In case of option 1 you should refix just to be sure.

 

[Sirius Glass]

I use Edwal Hypo Chek®.

 

[nworth]

One possibility is:

Residual silver test

Water 60 ml
Sodium sulfide 7.5 g
WTM 100 ml

Place a drop in a clear area of a print (border). Wait 5 minutes. A brown stain indicates the presence of silver and insufficient fixing.

I've seen other instructions that say that anything more than the slightest cream tone indicates insufficient fixation. Your eye is quite sensitive for this, but a negative result may not indicate what we usually mean by complete fixing.

 

[Doremus Scudder]

Question 1: Yes, it's easy to refix; just soak the prints, fix as usual and follow that with your usual wash-aid and wash sequence.

Question 2:
Unfortunately, there's not a really reliable and convenient test for print fixer (especially if you're using fiber-base paper). The fixer can be good and your paper still under-fixed if your times are not adequate. Edwal HypoCheck and other similar products don't give a negative result until the fixer is somewhat past exhausted (maybe okay if you're using two-bath fixing) and so is not accurate/reliable enough for me.

There are a couple things that are generally held to be best practice that you can add to your work flow to get some peace of mind.

Use throughput as a guide. Manufacturers give a capacity for their fixers in the form of so-and-so many 8x10s per liter (or gallon) of fix. The problem here is that there are different standards: "general purpose" and "optimum permanence." If you're after the best practice, then fix for optimum permanence. If you use the Ilford method of fixing prints in "film-strength" rapid fixer for only one minute, then the throughput capacity is only about 10 8x10s or equivalent per liter. I find this wasteful so I recommend...

Use two-bath fixing. Mix two identical fixing baths. Fix your prints for half the recommended time in the first bath and then transfer it to the second bath for the second half of the time. Keep track of the throughput of the general-purpose capacity for the volume of bath one. This is usually about 35-40 8x10s per liter. After the capacity has been reached, discard bath one and replace it with bath two. This can be repeated through 5-6 cycles before you need to mix both baths fresh. The second bath always stays relatively fresh and ensures fixing to optimum permanence as long as the throughput capacities are not exceeded.

To really know how your workflow is working, you need to test for residual silver. The Kodak ST-1 test (I think that's the formula given above) works well. So does concentrated selenium toner if you have that on hand. The procedure is to put a drop of the test solution on the white border of a fixed and full washed print, either the sulfide or KRST mixed 1+9 (some use concentrated KRST right out of the bottle). Wait 2-3 minutes and rinse off the drop. Any discoloration other than a very slight yellowing is indicative of inadequate fixing. It's good to have a benchmark for the papers you are using buy testing a sheet known to be fixed and washed well, e.g., one that is the first through the fixer and for longer time than necessary and washed longer than needed as well. Then you'll know what color to expect from subsequent tests. If a test turns up darker, then you need to refix and adjust your workflow so that you don't have the problem in the future. FWIW, I test the last print through the fix and wash for each session for both residual silver and residual hypo (to test for adequate washing).

Doing the tests is the only practical way I've found of really knowing if your prints are being correctly processed. There's a ton in info here about both those tests if you just do a search.

Best,

Doremus

 

[Ko.Fe.]

I also prefer Ilford Rapid Fixer for paper.
I don't know about OP printing quantities, but I know it is possible to calculate.

After having similar as in OP question I committed RTFM:
http://www.ilfordphoto.com/Webfiles/2006130218312091.pdf

And I realized, what I'm always OK with maximum dilution for 1L of working mix for maximum amount prints I'm able to print at once.

In fact, in my case, fixer mix is strong enough to re-use for several rolls of film. And it is very easy to test fixer with film.

 

[Gerald C Koch]

The problem with the various tests for hypo, whether for papers or the bath itself is that they are all rather subjective. The best method is just to keep track of how many 8X10 sheets or equivalent have passed through a particular bath. Then do not exceed the manufactures recommendation for the fixer. Very simple and best for archival permanence. In addition use a two bath system.

 

[gone]

Clip test.

 

[nworth]

Fixer is cheap. Since it is hard to tell when it is exhausted, simply change it often. I usually use my print fixer for one session only (single bath), or at most two if I haven't done a lot of prints. Most manufacturers list the capacities for their fixer products, and some list tray life. For instance, Kodak says that their Rapid Fixer with Hardener will fix about 100 8X10 sheets per gallon (26 per liter) and will last up to 1 week in the tray or up to one month in a tank. I would cut those estimates a bit to 15 - 20 sheets per liter, just to be sure. The other Kodak fixers have similar capacities and lives. Most rapid fixers are pretty similar in composition, so this may be a good estimate for others. Note the tank life. Fixer does not last forever in a storage bottle.

Be sure to fix for the full recommended time. The danger of underfixing is greater than that of overfixing. Fix one print at a time, and agitate continuously during fixing. Prints fix more slowly and wash with more difficulty as the fixer becomes exhausted. The manufacturer's recommended time is usually adequate even near the end of the recommended capacity.

 

[Doc W]

Quite a few of you have recommended keeping track of throughput, which is a pain, but I think that in the long run, it might be the easiest for me. So tomorrow I am going to put a white board behind the fixer trays (I already do two baths) and keep count.

Thanks a lot. This was a helpful thread for me.