Quote Originally Posted by Photo Engineer
Silver Iodide 'appears' to be insensitive to light due to the fact that it is almost non-developable. So, there may be a great amount of latent image, but you need a very unique developer to reveal that image.
Relative to salt prints, though, it's not a question of developing (unless you're doing calotype), but whether the silver can reduce and the iodide can continue to draw silver from the nitrate salt in the sensitizer (a reaction I'd normally expect only if there were sufficient water present, but lots of things act like there's plenty of water in what I think of as dry material). In that environment, I'd think iodide would be (again) faster than bromide. I've heard from another APUG member who comfirms that potassium bromide produces salt prints about two stops faster than sodium chloride, but with reduced range; using an iodide salt seems likely to be further along the spectrum, while fluoride would be at the other end (slower, but with broader range) if one can manage to get it to print out at all.

BTW, where I've read of silver iodide as insenstive was in reference to preparing calotypes -- the paper is pretreated with potassium iodide and then silver nitrate, and exposed to sunlight; this pre-exposure, producing latent image exposure overall, might be part of what makes the calotype so much faster than a common salt print (along with incorporating a developing agent, gallic acid, and then developing out the image with more gallic acid and keeping plenty of excess silver nitrate throughout).