Hypo, fixer testing, and bromoil

I've read literally scores of posts here regarding fixer for fiber paper... and I thought gay marriage and guns were controversial. (Hey, I'm a liberal in Texas!)

I'm about to do some Bromoils using plain Hypo as fixer (suggested by some to make inking easier, and controversial as well, some say rapid fix is just fine).

I've found a wide range of suggested exhaustion for hypo (penta) at 250G/liter - ranging from 10-20 8x10's. Doing the standard leader test and monitoring clearing time for doubling of time to clear sounds reasonable. But does that address the 2 sides of fixer life, which I understand to be fixer exhaustion vs. silver level?

Then I came across this APUG post (didn't record the author in my notes):

"...suppose you took a sheet of photo paper, put a penny every 2cm or so, then expose it to a very bright light, the emulsion will turn darker on it's own, cut it into squares, and keep it in an old paper box. Before starting a session, you do the same test, when the circle from the penny disappears, that's your clear time. if it takes too long, replace the fixer."

Now throw in that I'll use rapid fix for all regular printing and plain hypo just for bromoil matrices (which I'm doing around 11x14 size)... which go through the additional bleach and fix steps. I'd like to at least entertain the ability to use the fixer from my initial printing of matrices for the post-bleach fixing, so a reliable way to test fixer would be welcomed. (Initial test prints I can do with rapid fix as those get discarded).

As a side question - for bromoil work, is 2-bath fixing necessary for the initial exposure steps? Necessary for the post-bleach fixing? Does the bleaching, re-fixing and final washing make the initial fixing less important - is a basic shot in the fixer going to be fine for a print that is about to be re-washed and bleached and fixed again? I'm an err on the side of caution type, but if wasting time & materials can be avoided, I'm in. Thanks for any insights!

As you know, film is mostly Silver Bromide and Silver Iodide, whereas paper is mostly Silver Chloride and Silver Bromide. Silver Chloride is more soluble than Silver Bromide, which in turn is more soluble than Silver Iodide. Why is this relevant? If you test paper fixer with film clips, you test a fixer that may be loaded with Silver, Chloride and Bromide ions with a test clip that has mostly Silver Bromide and Silver Iodide. Result: the film clip will respond much less to fixer exhaustion than you would expect. It will "see" the Silver and Bromide ions, but the Chloride ions, which will affect paper fixing, will not change film clip clearing time.

The advantage of two bath fixing is that you can fix more prints with the same amount of fixer. If you process only very few prints, a single fixer bath will suffice. For example, Ilford says you can fix 10 8x10" prints per liter in single fixer bath, but 40 sheets in two bath fixing. Since you use the second fixer bath as first bath during the next session, your savings in fixer are fourfold.

I see no reason why Rapid Fixer can't be used in this process. I think the references demanding "plain hypo fixer" come from a time when many fixer formulas included a hardener, and the phrase "use plain hypo" was not aimed against Rapid Fixers but against hardening fixers.

Rudi is right, you need to test the materials you are using, so using film to test paper fixation is not going to give you reliable results.

There are ways to do "clip tests" with paper, but they tend to be fiddly and they are not really backed up with a clear database of results that give an easy rule of thumb for time. What I'm trying to say is that there's no easy "double the clearing time" type guideline for paper. You'd have to clip test and then residual silver test your different papers and come up with a factor for each. Again, way too much work.

The best and simplest test for proper fixation is the residual silver test. You can use the classic sulfide test (Kodak ST-1) or, alternatively (and easier for those of us that always have Kodak Rapid Selenium Toner on hand) you can use selenium toner as a residual silver test.

Here's the ST-1 info:

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. Squeegee your print or film and place one drop of the working solution on a border area. Let it sit for 3 minutes and 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.
[Information taken from Processing Chemicals and Formulas for Black-and-White Photography, Kodak Publication No. J-1, Eastman Kodak Company, 1973.]

For a thorough discussion of using KRST either undiluted or in the Kodak recommended 1+9 dilution, see here.
(there was a url link here which no longer exists)

I find that establishing a workflow for your material(s) using two-bath fixing, and then pushing the capacity to the point of exhaustion once gives one an idea of just how far you can push the system. Then figure in a generous safety factor, since actual capacity of a fixing bath depends on the amount of undeveloped silver halides fixed out, which varies from print to print (lots of high-key prints will exhaust fixer faster than lots of very heavy, dense prints).

Then, all you really have to do is test the last print through the fixer after washing each time you print. Really easy if you leave a border and have the test solutions on hand. I do this as well as the residual hypo test (Kodak HT-2) for each fixer batch (i.e., before I change bath 2 to bath 1 and mix a new bath 2).

Then you'll know for sure, no guessing, no worrying and no question about it, if your prints are adequately fixed. If your test shows residual silver, then return the last 5-10 prints to the fixer for refixing.

FWIW, I have standardized on 36 8x10 prints per liter of bath 1 with Ilford Hypam or Rapid fix in the 1+9 dilution.

Best,

Doremus

Sir, that is exactly what I was hoping to find. I'd come across some info on ST-1 but nothing concise, mostly comments pointing to long-gone web pages. And a recipe that needs only one chemical stocked? That's like dessert.

I'm back in the darkroom after a couple decades off, and standardizing much of my workflow is my goal.

Regarding Bromoil fixing - I've found several comments regarding Ilford Rapid Fix, and discussion of specifically non-hardening fixers vs. hypo. Some feel it made a night & day change, others seem fine with Ilford. Bromoil being what it is, fixer choice may have much to do with paper, soaking time, etc. Or it may be one of those things that when tested carefully proves to be moot. So, I'll test with that as the only variable (if you can ever consider Bromoil as variable-free, the dang phases of the moon seem to affect it for all I know...)

Anyway, thanks again!

Photo Formulary sells both the raw compound and a ready to use residual silver test. Before you stock up on Sodium Sulfide: please be aware that this compound releases a highly toxic gas (Hydrogen Sulfide), if it ever ends up in an acidic liquid. Make sure you know, what this compound does, how it reacts and how you need to handle and store it. There are a few compounds in photo chemistry which don't allow for mistakes, and this is one of them.

Thanks Rudeofus - I recall coming across that warning last week.

Generally, for anything beyond standard processing chemicals, the inside of my chemistry cupboard doors have become handy bulletin boards for materials handling and instructions. Containers that don't have explicit safety labeling get DIY labels (so in the case of SS, there will be a "NO ACID!!!" label.)

I have found that treating myself like a preschooler with a head injury is often a wise course of action.