good news, using regular, non-iodized salt works as a restrainer and can replace iodized salt or potassium bromide.
For the test I made a demanding setup, Rollei RPX 400 @ 800 stand developed @ 24 °C in Caffenol-C-L urgently needs a restrainer, without you will have huge problems concerning massive fog and uneven, cloudy, streaky development. Last afternoon I shot the 35mm film and cut it into 3 peaces. One was developed with 20 g/l regular non-iodized table salt aka sodium cloride. For the second piece 12 g/l iodized salt (0.0025 % iodate) was added and the third piece got the addition of the well working 1.2 g/l potassium bromide aka KBr.
Regular table salt without iodine (20 g/l) works good enough to prevent any streaks or uneven clouds in the image, that you will get with stand development if no restrainer is used. Yellowish stain and quite a lot base fog can be noticed. Again, base fog is not as evil as often told as long as the develoment is even. I guess that 30 or even 40 g/l will be fine for fast films.
Iodized salt (12 g/l), although much less is used, works slightly better with a bit less base fog, but still even enough developed that the image is not disturbed, only some unevennes at the borders where the spiral covered the film during development. And the stain is also less. Iodine does a good job. I would now adjust the salt to 15- 20 g/l for fast films, slow films need less salt.
You can see that KBr (1.2 g/l) gives the least fog and no stain, perfectly even developed, no surprise at all.
I couldn't notice any significant differences in grain or effective film speed. EI 800 was fine.
Here's an example with the regular table salt, no post processing exept a bit unsharp maskening and scaling. The neg was really quite dark due to the high base fog level. Do you notice any drawbacks? I can't. And increasing the amount of salt will probably reduce the fog. But most important, the development is even, no streaks, no clouds, simply fine.
It was a rainy day, so an orange filter was used. Probably I overdeveloped a little bit. It was really war in my lab and temp increased up to 25 or 26 °C during development. There's a break point in time and temp, if you exceed it, the RPX 400 shows immediately increased fog and grain. So that was probably a little bit too much. But all three chunks were developed simultanously under the same conditions.
These are my very first experiances. Go and try regular table salt and let me know how it works for you. It will work with other Caffenol variants to. Sharing your experiances via The new Caffenol Home on flickr is much appreciated.
Cheers - Reinhold
important update: my flickr buddy Rob showed that salt (sodium cloride) causes dichroic fog. Since iodized salt is widely available it's recommended to use it because you need much less salt and dichroic fog is less. Adjusting the amounts for your needs is quite easy. Potassium bromide still is the best restrainer but I love the idea of using commonly available agents.