Doing it wrong: Perfecting my Pan F Plus process

A negative example
An example negative from my most recent, science-informed developing session. I’m really pleased with the overall density and with the shadow and highlight detail. (Daniel J. Schneider)

Since moving into film a bit over 5 years ago (not counting the film photos I took as a kid) I’ve been slowly improving my development process. I’ve talked before about my favorite developer, Kodak HC-110.

Aside from trying some Ilford DD-X developer before trying HC-110, I’ve never used anything else. DD-X worked fine, and HC-110 worked fine, but HC-110 was cheaper on a per-roll basis. Long before ever running out of HC-110 (pretty much the only thing that would’ve led me to try something else) I started to learn about its incredible versatility. I’d also only just begun to learn how to really use it.

I’m also still working on the first bottle of Kodak Indicator Stop Bath I ever bought, and the first bottle of Photo-Flo. Of course, Photo-Flo seems to last forever — not only is the bottle 5 years old, I’ve barely made a dent.

The other thing that hasn’t changed is the fixer. I bought Ilford Rapid Fixer to start with because the day I went to buy chemicals, Denver Pro Photo was out of Kodak fixer. I had also chosen Ilford Delta 100 as my first film to learn with (I’ve posted some of those early photos), so Ilford fixer seemed sensible. Since it worked, I’ve never tried anything else.

As I’ve sought to improve my photography, one key thing I’ve focused on lately is producing a better negative. To that end I’ve examined each part of the process, most recently, how I fix the developed film. Thing is, I think I’ve been kinda doing it wrong all this time.

Ilford’s Rapid Fixer says right on the front that it can be mixed 1+4 or 1+9, right? And when to use each dilution is not as explicit in the data sheets as I’d like. Hoping to keep costs low, I figured I’d just use 1+9, because why not?

Inadequate fixing is why not. At least I think it’s been somewhat inadequate all this time.

Inadequate fixing and how to avoid it

Underfixing can cause several problems with the negatives:

  • It leaves the silver inadequately fixed to the base; negatives may not last as long in storage.
  • Negatives could be cloudy from undissolved silver halides that remain.
  • Highlight detail could be lower than desired from undissolved silver halides left among the denser silver areas.
  • Some emulsions may have a color cast from sensitizing dyes or anti-halation coatings trapped among remaining silver halides.

Overfixing has issues, too, in particular that it can destroy faint shadow detail or even bleach the negative completely. Of course, a couple minutes extra isn’t a big deal — but more than a few minutes beyond what’s needed could start to damage detail.

The solution is to fix properly, which requires testing and math. Fortunately, both the testing and the math are easy. The test you’ll need to perform is called a “clearing test.” You’re looking for how long it takes your fixer to clear the film completely, removing all the silver halides. The clearing test should be performed before each developing session until the fixer is exhausted; you may want to perform a clearing test after every couple of tanks, especially as it gets older.

To perform a clearing test:

  1. Pour a little fixer into a small bowl or measuring cup.
  2. Take a clipping of the same film emulsion (I’ve opted to sacrifice an entire roll of Pan F Plus for making clips, since I use this film almost exclusively), which has been exposed but not developed.
  3. Place a drop of fixer on the clip, or dip the end in the fixer.
  4. As soon as the film starts to clearly change color, start a timer and drop the entire clip in the fixer.
  5. When the spot or end you first exposed to the fixer and the rest of the film are indistinguishable from each other, the film should be clear — stop the timer.

The time you get is what’s called the “clearing time,” and you should fix your film for double that time. So here’s where the math comes in — multiply that time by two. This is your fixing time.

Another step to avoid underfixing is to move to a two-bath fixing procedure. For a two-bath process, you’ll need to start with a fresh batch of fixer as your second bath, and keep your existing fixer (assuming it’s not completely useless — clearing time probably still should be under 4-5 minutes) as your first bath.

A roll for clearing tests
Since I use Ilford Pan F Plus film almost exclusively these days, I decided to sacrifice a whole roll to be sure I can do clearing tests every time I start a developing session. (Daniel J. Schneider)

Fix your film in the first bath for one-third to one-half the total fixing time, then complete the fixing time in the second bath. This way a good portion of the silver you’ll be removing from your freshly-developed film will be clogging up the older, less-effective fixer. The fresh stuff stays cleaner and lasts longer. Once clearing tests indicate your second bath fixer is beginning to exhaust — clearing time going over 2-2.5 minutes — you demote it to being the first bath, and mix a fresh batch for the second bath.

How I applied the science

I started out using each batch of fixer I made for awhile and then sort of dumping it when it seemed like it wasn’t clearing my negatives. (Note: Be sure to dispose of used fixer properly — it’s full of soluble silver nitrate that can be quite devastating to anything organic.) I probably stretched my fixer dollars pretty far, but I think my negatives suffered for some or all of the reasons above.

After a year or so of that crap-shoot, I started mixing fresh fixer every other developing session (a session for me usually consists of 10-15 rolls of 35mm film, or 8-12 rolls of 120 film). Then I started mixing fresh every session. All the while I was still using 1+9 Ilford Rapid Fixer.

My favorite developing tank — a big, used Paterson I picked up cheap — handles 5 rolls of 35mm or 3 rolls of 120 at a time. Because it’s so big, I have to mix 1650 milliliters of each chemical to fill it. At the 1+9 dilution for Ilford Rapid Fixer, that means I need 165 milliliters of fixer in 1485 milliliters of water. At 1+4 dilution that doubles to 330 milliliters, though, which is more than half the 500 milliliter bottle that my local suppliers all carry. That difference was largely why I opted for the thinner solution.

So just for fun I did a clearing test on the fixer I had in the jug, which had been mixed just under two weeks earlier and used for 14 rolls of 120 film so far — fixing for 6 minutes in each case.

Less purple in my negs
Nine rolls of film developed after rethinking my fixing process and employing clearing tests. Notice how little purple shade there is — it was much worse in the past. (Daniel j. Schneider)

Okay, the result wasn’t as bad as I expected — considering that this was largely exhausted fixer, anyway — but the clearing test took about 3.5 minutes, meaning at least the last few rolls were definitely underfixed — probably the whole session to at least a small degree.

So I did some math based on all I’d read and discussed on Twitter about the fixer problem. I figured what really matters is that the film is fixed properly — not whatever dilution I use to achieve that. I figured I can use half a bottle exactly — 250 milliliters — and fill the rest out with water up to 1650mL. Do a clearing test and adjust fix time as needed. This works out to about 1+5.6, which is much closer to the higher-concentration recommended by Ilford than I’d been using.

Fresh 1+5.6 Ilford Rapid Fixer cleared in 1 minute, 10 seconds. Since I was going to be developing 9 rolls yesterday, I set my fix time at 4 minutes and just poured out a little early for the first couple tanks. A clearing test at the end of the session showed the same fixer with a clearing time of 1 minute, 21 seconds — still indicating a fix time of 4 minutes was more than enough.

Before the next session, I’ll start with a clearing test and expect to find close to the same time — I wonder if, perhaps, it will even go down as some of the silver precipitates out of the fixer solution?

I plan to keep using the same fixer until the clearing time goes beyond 3 minutes, adjusting my fix time as needed. Some discussions here and there suggest that longer fixing and longer washing — anything that extends the time your negatives stay wet — could increase grain size by allowing more clumping. While I haven’t yet been able to confirm that with credible documentation, I will nevertheless try to avoid using fixer that requires more than 6 minutes of fix time.