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Salt with black and white film...?

Posted on 25 February, 2024 / 5 min read

I saw a post on Facebook a while ago claiming that adding 30g/1L of salt to BW developer would help with contrast and base fog. I looked a bit deeper into it and found various claims. Well, it's cheap, and I do have a whole lot of Ilford Surveillance P4 film that could benefit from higher clarity at lower speed.

But no one seemed to bother making a proper side by side comparison. So I'll give it a try.

The setup

Minolta XD, two rolls, 12 exposures each. 24mm f2.8 at f8, so lack of sharpness of the lens would not hide any flaws of the process. Tripod, release cable and a varied scene, with both highlights and shadows. Not at home, I don't have environment good enough that reciprocity failure wouldn't kick in, possibly screwing with the exposure.

After loading, two shots at ISO 12, to offset initial light leaks, then 1 each for 25, 50, 100, 200, 400, 800, 1600. Two for 3200, actually. Changing ISO setting in camera.

As at 1600 f8 was too bright, I closed the lens down to f16. For 3200 f16 also seemed to be too fast, so I shot one at f16, one at f22, in case camera would overexpose the first image.

As I loaded the non-salt roll at home, it was not affected by light piping; the salty one was, so two exposures at EI 12 was a good choice. Mostly interested in 50-400 range anyway.

Developed in HC-110 H (1+64), 11 minutes - the usual I do for Ilford Surveillance P4 exposed at EI 100 which is my go-to. Added 9g of salt for 300mL of developing solution for the second roll. Stopped and fixed as usual.

The results

I noticed that HC-110H foams a fair bit on its own, but with salt added it does not anymore.

The salt roll had some issue with fixing, seemingly? I refixed it and it didn't help much. It does not happen every time.

Just by looking at the negatives, can't see much of a difference in the base density or anything between the two strips, top is non-salt, bottom is salt at EI 50-200:


Scanned with usual method. Left is always without salt, right with. Feel free to click on the images to get the full resolution.

EI 12

EI 25

EI 50

EI 100

EI 200

EI 400

EI 800

EI 1600

EI 3200 (f16)

EI 3200 (f22)


The no salt images have higher contrast, but that could be a scanning issue (and I'm too lazy to adjust). I am surprised that there do seem to be better shadow detail in images with salt - look at the entrance of the funeral home, especially at EI up to 400, over that the image becomes an overall mess. What I was hoping for, which is less visible grain, did not occur.

Will I keep doing adding salt? Maybe. All in all though the difference seems negligible, only if you peep. Contrast is of no worry to me as that is usually adjusted in post.