I have several times read that when you have expired film with some fogging you should use a cold developer. This goes against my gut feeling, which says that the longer you develop fogged material the more fog you will see. This is true for paper, and should be true for film. So shouldn’t the opposite be true? That you want a HOT developer so you can develop for a shorter period of time?
My own experience tells me that if you have slightly expired films, more active developers work better. I have a lot of Neopan 400 that expired about a decade ago and when developing in Fuji SPD which gives development times of just a couple of minutes, there is zero fogging. But when I tested a roll in Spur Acurol-N, the development was for around 20 minutes and there was loads and loads of fog. Semi-stand and stand development also gives loads of fog on expired material.
I decided I had to investigate this for myself to come to the bottom of things, since I have some 30 rolls of various films that are more or less fogged. I have two bricks of Agfapan 400, the precursor to the now famous APX400 film, that has slightly too much fog for getting a decent scan. In the darkroom it doesn’t matter too much, but when scanning it becomes a problem if you have too much base fog.
So what I did was I developed snippets at 16c, 20c, 24c and 28c and then measured the base fog with my non-scientific method, which is to scan the strips together on my flat bed scanner and then use the color picker in Photoshop to see what the color of the film base is. It is rudimentary, but it does work for my purposes. I am hoping to be able to find a densitometer in the future so I can do these tests faster and with more scientific rigor. I also developed a snippet at 20c but added 3ml of benzotriazole 1% to the 300ml of developer.
The results were interesting to say the least. It seems the fogging increases at 16c, as expected. The longer development time will start to fog the film base. Fogging is lower at 20c, but higher at 24 and even higher at 28. So shorter does not always mean better. It seems to me that the amount of fog is a function dependent on both development length and developer activity (ie temperature). Both will increase fogging, but there is a sweet spot somewhere around 20-22c, for Xtol 1+1 at least. It would be interesting to see if this is true for more developers.
The BZT addition works really well, as expected. It is a really powerful anti-fogging agent, but it will also reduce film speed very quickly. What you want to do is to add just enough to reduce SOME fogging, but not more than that. At the level I tested at, my guesstimate is that I lost about a 1/2-1 stop of effective film speed.
After these initial tests, I also wanted to see if it is true that some developers are better than others for expired film. I didn’t have any HC110 at hand unfortunately, which is often hailed as the king of developers for expired film. But Rodinal has also often come up as a good developer due to it not giving full film speed and you can alter dilutions to find a time that works. I also had a little bottle of FX-39 II I am working on to do a full evaluation of. Again, results were surprising. The Rodinal was not at all a good developer, as I had expected. This is an ancient developer, while good for a lot of things, in my experience it both increases fog and also reduces effective film speed. However, FX-39 was really good. The difference was not huge compared with XTOL 1+1, but a difference nevertheless. It was close to the completely clear strip that was developed together with BZT. This may be due to underdevelopment though.
Keep in mind, I developed just one snippet of film, once. It is possible variations occurred due to inconsistent agitation, temperature fluctuations, cosmic rays, whatever. At these very small amounts of developer you also have an increased risk of miscalculating the dilutions. I hope to do some more research on this in the future. Please share if you have some results of your own, write in the comments.
Anyhow, here are the results in a chart. Don’t pay too much attention to the numbers, they only mean something to me in this particular test. But 0 is no fog, and my personal limits are something like 0.5 for darkroom printing and 0.3 for scanning. As you can see, developer choice and temperature choice can lead to either unusable negatives or perfect negatives.
Key takeaways
XTOL 1+1 is a pretty good developer for expired film
20c seems to be a good sweet spot
Film starts to get fogged after around 10min due to time in developer
Film starts to get fogged at around 24c due to increased activity of developer
Rodinal is not a good developer for expired film
FX-39 is a very good developer for expired film
Things to investigate another time
Does different Rodinal diltutions affect fogging?
Is prewashing expired film good or bad?
Is HC-110 really that good in comparison with other modern developers?
This subject has taken a lot of my time recently, but it has been interesting. Please buy my zines, available in the shop here on the site! That’s it for this time, write in the comments if you like more of this kind of technical content.